Lighting: lighter night floor (0.18 -> 0.24)

Night was a touch too dark; raise the ambient moonlight floor a couple points.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CLAUDE.md

@@ -27,14 +27,26 @@ is the living showcase — new engine features are demonstrated there.
 
 Engine libraries (each feature is a namespaced subfolder of its host):
 
-- **`Core`** — game loop, ECS world, scenes, time (`GameClock` with `TimeScale`; `GameSpeed`
+- **`Core`** — the platform-free kernel: ECS world, scenes and transition timing, time
-  for discrete pause/1×/3×/6× speed control over the clock, `context.UseGameSpeed(...)`;
+  (`GameClock` with `TimeScale`; `GameSpeed` for discrete pause/1×/3×/6× speed control over
-  `Calendar` turning scaled time into in-game days, `context.UseCalendar(secondsPerDay)`),
+  the clock, `context.UseGameSpeed(...)`; `Calendar` turning scaled time into in-game days,
-  plus **Input** (`MrGameEng.Input`: `InputManager`, `ActionMap`, `InputSystem`, in
+  `context.UseCalendar(secondsPerDay)`; `Climate` — continuous seasonal/daily temperature
-  `Core/Input/`). Depends only on MonoGame and Friflo.Engine.ECS.
+  and season over the calendar, `context.UseClimate(settings)`), services, logging, and
+  **`HeadlessHost`** — a fixed-timestep loop without a window or GPU (dedicated servers,
+  batch simulation, tests). Depends only on Friflo.Engine.ECS — no MonoGame, no platform.
+- **`Host`** — the windowed MonoGame host: `GameHost` (wraps `Game`, owns the window and
+  `GraphicsDeviceManager`, publishes `GraphicsDevice` as a service), visual scene
+  transitions (`OverlayTransition`, `Transitions.Fade/Wipe`, `TransitionRenderer`), plus
+  **Input** (`MrGameEng.Input`: `InputManager`, `ActionMap`, `InputSystem`, in
+  `Host/Input/`). Nothing depends on `Host` except the game itself. → `Core`.
 - **`Graphics`** — custom batched renderer, camera, sprites, plus **Tilemaps**
   (`MrGameEng.Tilemaps`: code-built tile grids rendered through the batcher,
-  `scene.UseTilemaps()` after `UseRenderer2D()`, in `Graphics/Tilemaps/`). → `Core`.
+  `scene.UseTilemaps()` after `UseRenderer2D()`, in `Graphics/Tilemaps/`) and **Lighting**
+  (`MrGameEng.Lighting`, `Graphics/Lighting/`: day/night ambient over the `Calendar` driving
+  `Renderer2D.AmbientLight` on world layers, `scene.UseDayNight(renderer)`; plus a per-cell
+  **lightmap** — `LightmapBuilder` (ambient × occlusion + point lights with grid-traced shadows),
+  `PointLight` component, multiplied over the world via `scene.UseLighting(...)`, sampleable with
+  `Lighting.SampleAt` for the simulation). → `Core`.
 - **`Audio`** — ogg playback (NVorbis); `AudioManager` with `SoundVolume`/`MasterVolume`
   (one knob for effects + music). → `Core`.
 - **`Content`** — the asset/content pipeline: **Assets** (`MrGameEng.Assets`: runtime
@@ -52,6 +64,13 @@ Engine libraries (each feature is a namespaced subfolder of its host):
   **Collisions** (`MrGameEng.Collisions`: `Collider` component, spatial hash rebuilt per
   tick, pairs/queries/raycast, `scene.UseCollisions()` after movement systems).
   → `Core`, `Graphics` (Collisions needs `Transform2D`, `RectF`).
+- **`Net`** — multiplayer building blocks, browser-compatible by design: a dependency-free
+  RFC 6455 WebSocket server over `TcpListener` (browsers can't speak UDP, so WebSocket is
+  the engine's one transport), a `ClientWebSocket`-based client (works in Blazor WASM),
+  both behind the poll-based `INetConnection`; server-authoritative component replication
+  (`ReplicationSchema` of unmanaged components, `ReplicationServer` sending per-connection
+  deltas — no acks needed over a reliable ordered transport, `ReplicationClient` applying
+  snapshots to a local store, `NetId`). → `Core`.
 - **`UI`** — Myra integration (`scene.UseUI()` after `UseRenderer2D()`),
   **DevConsole** (`MrGameEng.DevConsole`: in-game console capturing `Core.Log`,
   `scene.UseDevConsole()` last in OnLoad) and **Inspector** (`MrGameEng.Inspector`: a
@@ -63,9 +82,13 @@ Engine libraries (each feature is a namespaced subfolder of its host):
   netstandard2.0 analyzer.
 
 Dependency rule: a library may depend only on `Core` and `Graphics`; `Core` depends only
-on MonoGame and Friflo.Engine.ECS. Features grouped into one library share its package
+on Friflo.Engine.ECS (no MonoGame — the simulation must run headless). MonoGame is pulled
-set (e.g. `Content` carries both FontStash and StbImage) — keep optional/heavy deps
+in by the platform/graphics libraries (`Host`, `Graphics`, `Audio`). Platform resources
-(Myra, NVorbis) in their own library so the rest of the engine stays free of them.
+(e.g. `GraphicsDevice`) are published by hosts as services in `EngineContext.Services`;
+graphics code reaches the device via `context.GetGraphicsDevice()` (extension in
+`Graphics`). Features grouped into one library share its package set (e.g. `Content`
+carries both FontStash and StbImage) — keep optional/heavy deps (Myra, NVorbis) in their
+own library so the rest of the engine stays free of them.
 
 ## Commands
 

Directory.Build.props

@@ -1,5 +1,4 @@
 <Project>
-
   <PropertyGroup>
     <LangVersion>latest</LangVersion>
     <Nullable>enable</Nullable>
@@ -13,5 +12,4 @@
   <PropertyGroup Condition="$(MSBuildProjectName.StartsWith('MrGameEng.')) AND !$(MSBuildProjectName.EndsWith('.Tests')) AND !$(MSBuildProjectName.EndsWith('.Generator')) AND !$(MSBuildProjectName.EndsWith('.Sample'))">
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
   </PropertyGroup>
-
 </Project>

MrGameEng.sln

@@ -39,6 +39,14 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MrGameEng.UI.Tests", "tests
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MrGameEng.Audio.Tests", "tests\MrGameEng.Audio.Tests\MrGameEng.Audio.Tests.csproj", "{4407F6E6-0B65-41A3-ADFA-B78684A9B918}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MrGameEng.Host", "src\MrGameEng.Host\MrGameEng.Host.csproj", "{59818072-0D2B-4007-A50F-1343FA189EC6}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MrGameEng.Host.Tests", "tests\MrGameEng.Host.Tests\MrGameEng.Host.Tests.csproj", "{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MrGameEng.Net", "src\MrGameEng.Net\MrGameEng.Net.csproj", "{A4E754C7-C5FD-43A2-B345-34152D3A22D1}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MrGameEng.Net.Tests", "tests\MrGameEng.Net.Tests\MrGameEng.Net.Tests.csproj", "{434C24AC-08C6-483E-A2DE-6DBC8A4DE791}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -229,6 +237,54 @@ Global
 		{4407F6E6-0B65-41A3-ADFA-B78684A9B918}.Release|x64.Build.0 = Release|Any CPU
 		{4407F6E6-0B65-41A3-ADFA-B78684A9B918}.Release|x86.ActiveCfg = Release|Any CPU
 		{4407F6E6-0B65-41A3-ADFA-B78684A9B918}.Release|x86.Build.0 = Release|Any CPU
+		{59818072-0D2B-4007-A50F-1343FA189EC6}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{59818072-0D2B-4007-A50F-1343FA189EC6}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{59818072-0D2B-4007-A50F-1343FA189EC6}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{59818072-0D2B-4007-A50F-1343FA189EC6}.Debug|x64.Build.0 = Debug|Any CPU
+		{59818072-0D2B-4007-A50F-1343FA189EC6}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{59818072-0D2B-4007-A50F-1343FA189EC6}.Debug|x86.Build.0 = Debug|Any CPU
+		{59818072-0D2B-4007-A50F-1343FA189EC6}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{59818072-0D2B-4007-A50F-1343FA189EC6}.Release|Any CPU.Build.0 = Release|Any CPU
+		{59818072-0D2B-4007-A50F-1343FA189EC6}.Release|x64.ActiveCfg = Release|Any CPU
+		{59818072-0D2B-4007-A50F-1343FA189EC6}.Release|x64.Build.0 = Release|Any CPU
+		{59818072-0D2B-4007-A50F-1343FA189EC6}.Release|x86.ActiveCfg = Release|Any CPU
+		{59818072-0D2B-4007-A50F-1343FA189EC6}.Release|x86.Build.0 = Release|Any CPU
+		{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2}.Debug|x64.Build.0 = Debug|Any CPU
+		{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2}.Debug|x86.Build.0 = Debug|Any CPU
+		{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2}.Release|Any CPU.Build.0 = Release|Any CPU
+		{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2}.Release|x64.ActiveCfg = Release|Any CPU
+		{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2}.Release|x64.Build.0 = Release|Any CPU
+		{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2}.Release|x86.ActiveCfg = Release|Any CPU
+		{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2}.Release|x86.Build.0 = Release|Any CPU
+		{A4E754C7-C5FD-43A2-B345-34152D3A22D1}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{A4E754C7-C5FD-43A2-B345-34152D3A22D1}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{A4E754C7-C5FD-43A2-B345-34152D3A22D1}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{A4E754C7-C5FD-43A2-B345-34152D3A22D1}.Debug|x64.Build.0 = Debug|Any CPU
+		{A4E754C7-C5FD-43A2-B345-34152D3A22D1}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{A4E754C7-C5FD-43A2-B345-34152D3A22D1}.Debug|x86.Build.0 = Debug|Any CPU
+		{A4E754C7-C5FD-43A2-B345-34152D3A22D1}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{A4E754C7-C5FD-43A2-B345-34152D3A22D1}.Release|Any CPU.Build.0 = Release|Any CPU
+		{A4E754C7-C5FD-43A2-B345-34152D3A22D1}.Release|x64.ActiveCfg = Release|Any CPU
+		{A4E754C7-C5FD-43A2-B345-34152D3A22D1}.Release|x64.Build.0 = Release|Any CPU
+		{A4E754C7-C5FD-43A2-B345-34152D3A22D1}.Release|x86.ActiveCfg = Release|Any CPU
+		{A4E754C7-C5FD-43A2-B345-34152D3A22D1}.Release|x86.Build.0 = Release|Any CPU
+		{434C24AC-08C6-483E-A2DE-6DBC8A4DE791}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{434C24AC-08C6-483E-A2DE-6DBC8A4DE791}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{434C24AC-08C6-483E-A2DE-6DBC8A4DE791}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{434C24AC-08C6-483E-A2DE-6DBC8A4DE791}.Debug|x64.Build.0 = Debug|Any CPU
+		{434C24AC-08C6-483E-A2DE-6DBC8A4DE791}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{434C24AC-08C6-483E-A2DE-6DBC8A4DE791}.Debug|x86.Build.0 = Debug|Any CPU
+		{434C24AC-08C6-483E-A2DE-6DBC8A4DE791}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{434C24AC-08C6-483E-A2DE-6DBC8A4DE791}.Release|Any CPU.Build.0 = Release|Any CPU
+		{434C24AC-08C6-483E-A2DE-6DBC8A4DE791}.Release|x64.ActiveCfg = Release|Any CPU
+		{434C24AC-08C6-483E-A2DE-6DBC8A4DE791}.Release|x64.Build.0 = Release|Any CPU
+		{434C24AC-08C6-483E-A2DE-6DBC8A4DE791}.Release|x86.ActiveCfg = Release|Any CPU
+		{434C24AC-08C6-483E-A2DE-6DBC8A4DE791}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -249,5 +305,9 @@ Global
 		{C34F2AFF-F2B0-4AC4-A6F9-B114A06FB272} = {0AB3BF05-4346-4AA6-1389-037BE0695223}
 		{7F7D9641-2409-40CB-88A9-56BCE8C90A45} = {0AB3BF05-4346-4AA6-1389-037BE0695223}
 		{4407F6E6-0B65-41A3-ADFA-B78684A9B918} = {0AB3BF05-4346-4AA6-1389-037BE0695223}
+		{59818072-0D2B-4007-A50F-1343FA189EC6} = {827E0CD3-B72D-47B6-A68D-7590B98EB39B}
+		{B3EB5318-5EC0-4F23-8ECA-0EC5A0C4DFD2} = {0AB3BF05-4346-4AA6-1389-037BE0695223}
+		{A4E754C7-C5FD-43A2-B345-34152D3A22D1} = {827E0CD3-B72D-47B6-A68D-7590B98EB39B}
+		{434C24AC-08C6-483E-A2DE-6DBC8A4DE791} = {0AB3BF05-4346-4AA6-1389-037BE0695223}
 	EndGlobalSection
 EndGlobal

docs/architecture.md

@@ -33,11 +33,13 @@
 
 | Библиотека (сборка)          | Фичи (неймспейсы) и ответственность                        |
 |------------------------------|------------------------------------------------------------|
-| `MrGameEng.Core`             | Игровой цикл (хост над `Game`), `EntityStore`, `SystemRoot`, сцены, время (`GameClock.TimeScale`; `GameSpeed` — дискретная скорость пауза/1×/3×/6× поверх часов; `Calendar` — игровые дни поверх масштабированного времени, `context.UseCalendar(...)`), жизненный цикл. **Input** (`MrGameEng.Input`, `Core/Input/`): клавиатура, мышь, геймпад, action maps |
+| `MrGameEng.Core`             | Платформо-независимое ядро (зависит только от Friflo): `EngineContext`, `EntityStore`, `SystemRoot`, сцены и переходы (тайминг — `Transition`, `SceneManager`; визуал переходов — в `Host`), время (`GameClock.TimeScale`; `GameSpeed` — дискретная скорость пауза/1×/3×/6× поверх часов; `Calendar` — игровые дни поверх масштабированного времени, `context.UseCalendar(...)`; `Climate` — непрерывная сезонная/суточная температура и сезон поверх календаря, `context.UseClimate(...)`), жизненный цикл, `ServiceRegistry`, `Log`. **`HeadlessHost`** — цикл без окна и GPU на фиксированном тике (`Tick`/`RunTicks`/`Run` с realtime-пейсингом): дедикейтед-серверы, батч-симуляция, тесты |
-| `MrGameEng.Graphics`         | Собственный батчер-рендерер (см. «Рендеринг»), камера, спрайты, анимации, слои. **Tilemaps** (`MrGameEng.Tilemaps`, `Graphics/Tilemaps/`): тайловые карты кодом — `TileGrid` + `TileSet` + компонент `Tilemap`, отрисовка видимых клеток через батчер |
+| `MrGameEng.Host`             | Оконный MonoGame-хост: `GameHost` (обёртка над `Game` — цикл, окно, `GraphicsDeviceManager`; публикует `GraphicsDevice` сервисом в контексте), визуальные переходы сцен (`OverlayTransition`, фабрики `Transitions.Fade/Wipe`, `TransitionRenderer`). **Input** (`MrGameEng.Input`, `Host/Input/`): клавиатура, мышь, геймпад, action maps |
+| `MrGameEng.Graphics`         | Собственный батчер-рендерер (см. «Рендеринг»), камера, спрайты, анимации, слои. **Tilemaps** (`MrGameEng.Tilemaps`, `Graphics/Tilemaps/`): тайловые карты кодом — `TileGrid` + `TileSet` + компонент `Tilemap`, отрисовка видимых клеток через батчер. **Lighting** (`MrGameEng.Lighting`, `Graphics/Lighting/`): амбиент день/ночь поверх `Calendar` → `Renderer2D.AmbientLight`, `scene.UseDayNight(renderer)`; по-клеточный лайтмап — `LightmapBuilder` (амбиент × окклюзия + точечные `PointLight` с трассировкой теней), накладывается multiply поверх мира через `scene.UseLighting(...)`, сэмплируется `Lighting.SampleAt` |
 | `MrGameEng.Audio`            | Звуковые эффекты и музыка (NVorbis); `AudioManager` с `SoundVolume`/`MasterVolume` (одна ручка на эффекты и музыку) |
 | `MrGameEng.Content`          | Пайплайн контента. **Assets** (`MrGameEng.Assets`): runtime-загрузка без Content Pipeline, кэш, `AssetRef<T>`. **Atlases** (`MrGameEng.Atlases`): текстурные атласы — сборка из дерева картинок (`AtlasBuilder`) и рантайм-загрузка (`TextureAtlas`), CLI `tools/MrGameEng.AtlasTool`. **Mods** (`MrGameEng.Mods`): система модов — порядок загрузки, JSON-дефы, локализация, слияние деревьев контента |
 | `MrGameEng.Simulation`       | Детерминированные геймплей-примитивы без данных мира. **Pathfinding** (`MrGameEng.Pathfinding`): A*, Dijkstra, BFS, flow fields по гриду. **AI** (`MrGameEng.AI`): utility-ИИ — кривые отклика, соображения, действия, выбор (`UtilityAi<TContext>`), `Blackboard`. **Collisions** (`MrGameEng.Collisions`): компонент `Collider`, spatial hash, пары/запросы/raycast |
+| `MrGameEng.Net`              | Мультиплеер, совместимый с браузером по построению: WebSocket-сервер (RFC 6455 поверх `TcpListener`, без зависимостей — браузер не умеет UDP, поэтому транспорт движка один — WebSocket), клиент на `ClientWebSocket` (работает в Blazor WASM), оба за poll-интерфейсом `INetConnection`; server-authoritative репликация компонентов: `ReplicationSchema` (unmanaged-компоненты, до 32 типов), `ReplicationServer` (пер-соединенческие дельты против последнего отправленного — ack не нужны поверх надёжного упорядоченного транспорта), `ReplicationClient` (применение снапшотов в локальный `EntityStore`), компонент `NetId` |
 | `MrGameEng.UI`               | Игровой UI на [Myra](https://github.com/rds1983/Myra): `Desktop` на сцену, виджеты, скининг. **DevConsole** (`MrGameEng.DevConsole`): ингейм-консоль — логи `Log`, команды, история, автодополнение. **Inspector** (`MrGameEng.Inspector`): ECS-дебагер в духе Chrome DevTools — дерево сущностей по архетипам, компоненты/поля с правкой простых полей, выбор кликом по миру с подсветкой, вкладка перфа рендера (`scene.UseInspector(renderer)`, F1) |
 | `MrGameEng.Assets.Generator` | Roslyn incremental source generator: классы с типизированными хендлами ресурсов (отдельный анализатор netstandard2.0) |
 
@@ -69,19 +71,28 @@
 ### Правило зависимостей
 
 ```
-MrGameEng.Audio       ─┐
+MrGameEng.Host        ─┐
-MrGameEng.Graphics    ─┼──► MrGameEng.Core ──► MonoGame.Framework.DesktopGL
+MrGameEng.Audio       ─┤
-                       │                   └──► Friflo.Engine.ECS
+MrGameEng.Net         ─┤
+MrGameEng.Graphics    ─┼──► MrGameEng.Core ──► Friflo.Engine.ECS
+                       │
 MrGameEng.Content     ─┤
 MrGameEng.Simulation  ─┤                         (Content — за Texture2DRegion,
 MrGameEng.UI          ─┴──► MrGameEng.Graphics    Simulation/UI — за Transform2D/рендер)
 ```
 
-Библиотека зависит **только от `Core` и `Graphics`**. `Core` зависит только от MonoGame
+Библиотека зависит **только от `Core` и `Graphics`**. `Core` зависит только от Friflo —
-и Friflo. Если двум библиотекам нужен общий тип — он переезжает в `Core` (или, если это
+ни MonoGame, ни другой платформы: благодаря этому симуляция запускается и без окна
-графический тип, в `Graphics`). `Content` тянет `Graphics` (атласы выдают
+(`HeadlessHost`). MonoGame (`MonoGame.Framework.DesktopGL`) тянут платформенные и
-`Texture2DRegion`); `Simulation` тянет `Graphics` (`Collisions` использует `Transform2D`,
+графические библиотеки: `Host`, `Graphics`, `Audio` (и транзитивно их потребители).
-`RectF`); `UI` — только `Core` (Myra рисует своим SpriteBatch).
+Платформенные ресурсы (например `GraphicsDevice`) хосты публикуют сервисами в
+`EngineContext.Services`; графический код достаёт девайс через
+`context.GetGraphicsDevice()` (расширение в `Graphics`). На `Host` не зависит никто,
+кроме самой игры — это точка входа оконной платформы. Если двум библиотекам нужен общий
+тип — он переезжает в `Core` (или, если это графический тип, в `Graphics`). `Content`
+тянет `Graphics` (атласы выдают `Texture2DRegion`); `Simulation` тянет `Graphics`
+(`Collisions` использует `Transform2D`, `RectF`); `UI` — только `Core` (Myra рисует
+своим SpriteBatch).
 
 Фичи, собранные в одну библиотеку, делят её набор пакетов (например, `Content` несёт и
 FontStash, и StbImage). Тяжёлые/опциональные зависимости (Myra, NVorbis) держим в
@@ -345,12 +356,15 @@ CLI-обёртка: `dotnet run --project tools/MrGameEng.AtlasTool -- <исто
 
 - `SceneManager` владеет активной сценой; обычное переключение откладывается до начала
   следующего кадра (сцена никогда не выгружается посреди собственного кадра).
-- `Scenes.Switch(scene, Transition.Fade(0.5f))` — переключение с визуальным переходом:
+- `Scenes.Switch(scene, Transitions.Fade(0.5f))` — переключение с визуальным переходом:
   фаза закрытия (старая сцена живёт) → своп при полном покрытии → фаза открытия.
   Тяжёлый `OnLoad` новой сцены скрыт за полностью закрытым экраном.
-- Встроенные переходы: `Transition.Fade(duration, color)` и `Transition.Wipe(duration, color)`
+- Тайминг-машина (`Transition` — длительности фаз, покрытие) живёт в `Core` и работает
-  (шторка). Свои — наследованием от `Transition` (рисование через `TransitionRenderer.Fill`
+  и в headless-контексте; визуал — в `Host`: встроенные `Transitions.Fade(duration, color)`
-  в нормализованных координатах экрана).
+  и `Transitions.Wipe(duration, color)` (шторка). Свои — наследованием от
+  `OverlayTransition` (рисование через `TransitionRenderer.Fill` в нормализованных
+  координатах экрана); `GameHost` рисует оверлей поверх сцены, читая
+  `Scenes.ActiveTransition`/`TransitionCoverage`/`TransitionPhase`.
 - Переходы идут по **unscaled**-времени: работают при паузе геймплея (`TimeScale = 0`).
 - Повторный `Switch` во время перехода заменяет целевую сцену, не перезапуская переход.
 

src/MrGameEng.Audio/MrGameEng.Audio.csproj

@@ -4,6 +4,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="MonoGame.Framework.DesktopGL" />
     <PackageReference Include="NVorbis" />
   </ItemGroup>
 

src/MrGameEng.Content/Assets/AssetManager.cs

@@ -2,6 +2,7 @@ using FontStashSharp;
 using Microsoft.Xna.Framework.Audio;
 using Microsoft.Xna.Framework.Graphics;
 using MrGameEng.Core;
+using MrGameEng.Graphics;
 
 namespace MrGameEng.Assets;
 
@@ -103,7 +104,7 @@ public sealed class AssetManager : IDisposable
     {
         using var stream = File.OpenRead(path);
         return Texture2D.FromStream(
-            context.GraphicsDevice,
+            context.GetGraphicsDevice(),
             stream,
             DefaultColorProcessors.PremultiplyAlpha
         );
@@ -123,7 +124,7 @@ public sealed class AssetManager : IDisposable
     }
 
     private static Effect LoadEffect(EngineContext context, string path) =>
-        new(context.GraphicsDevice, File.ReadAllBytes(path));
+        new(context.GetGraphicsDevice(), File.ReadAllBytes(path));
 }
 
 /// <summary>Wires the assets module into the engine.</summary>

src/MrGameEng.Content/Atlases/AtlasesEngineExtensions.cs

@@ -1,5 +1,6 @@
 using MrGameEng.Assets;
 using MrGameEng.Core;
+using MrGameEng.Graphics;
 
 namespace MrGameEng.Atlases;
 
@@ -14,6 +15,6 @@ public static class AtlasesEngineExtensions
     public static void UseTextureAtlases(this EngineContext context)
     {
         var assets = context.Services.Get<AssetManager>();
-        assets.RegisterLoader((_, path) => TextureAtlas.Load(context.GraphicsDevice, path));
+        assets.RegisterLoader((_, path) => TextureAtlas.Load(context.GetGraphicsDevice(), path));
     }
 }

src/MrGameEng.Content/Genetics/Allele.cs

@@ -0,0 +1,16 @@
+namespace MrGameEng.Genetics;
+
+/// <summary>
+/// A diploid gene slot: the two allele values an individual carries for one gene. Stored as floats
+/// for both gene kinds — a <see cref="GeneKind.Discrete"/> gene simply holds integral variant
+/// indices. How the pair becomes a single phenotype value is decided by the gene's
+/// <see cref="GeneKind"/> (see <see cref="Genome.Express"/>).
+/// </summary>
+public readonly record struct Allele(float A, float B)
+{
+    /// <summary>The average of the two alleles — the phenotype of a numeric gene.</summary>
+    public float Mean => (A + B) * 0.5f;
+
+    /// <summary>The lower (dominant) of the two alleles — the phenotype of a discrete gene.</summary>
+    public float Dominant => MathF.Min(A, B);
+}

src/MrGameEng.Content/Genetics/GeneDef.cs

@@ -0,0 +1,97 @@
+using System.Text.Json.Serialization;
+using MrGameEng.Formulas;
+using MrGameEng.Mods;
+
+namespace MrGameEng.Genetics;
+
+/// <summary>How a gene's two alleles are stored and expressed into a phenotype value.</summary>
+public enum GeneKind
+{
+    /// <summary>A continuous value; the phenotype is the average of the two alleles (hybrid blending).</summary>
+    Numeric,
+
+    /// <summary>
+    /// A discrete allele index in <c>[0, Variants)</c>; the lower index is dominant, so the
+    /// phenotype is <c>min(a, b)</c> — a higher (recessive) variant shows only when homozygous.
+    /// A two-variant discrete gene is effectively a flag.
+    /// </summary>
+    Discrete,
+}
+
+/// <summary>
+/// An organism-agnostic gene definition — the unit the whole gene system is built from. A
+/// <see cref="GeneDef"/> describes how to generate an individual's two alleles, how they mutate
+/// when bred, and how the gene <see cref="Effects"/> contribute to named phenotype traits via
+/// <see cref="Formula"/> expressions. Nothing here is plant-, animal- or human-specific, so the
+/// same machinery drives any organism and arbitrary hybrids (a genome can carry any mix of genes).
+/// </summary>
+public sealed class GeneDef : Def
+{
+    /// <summary>Whether the gene is continuous or a discrete dominant/recessive allele.</summary>
+    public GeneKind Kind { get; init; } = GeneKind.Numeric;
+
+    /// <summary>Numeric: the central value an allele is generated around.</summary>
+    public float Default { get; init; }
+
+    /// <summary>Numeric: lower clamp for generated and mutated allele values.</summary>
+    public float Min { get; init; } = float.NegativeInfinity;
+
+    /// <summary>Numeric: upper clamp for generated and mutated allele values.</summary>
+    public float Max { get; init; } = float.PositiveInfinity;
+
+    /// <summary>Numeric: relative spread of generated alleles around <see cref="Default"/> (allele = Default ± Spread·|Default|).</summary>
+    public float Spread { get; init; }
+
+    /// <summary>Numeric: relative magnitude of a mutation step (value ± Magnitude·|value|).</summary>
+    public float MutationMagnitude { get; init; } = 0.1f;
+
+    /// <summary>Discrete: number of allele variants, valued <c>0..Variants-1</c>.</summary>
+    public int Variants { get; init; } = 2;
+
+    /// <summary>
+    /// Discrete: relative weights for generating each variant (length <see cref="Variants"/>).
+    /// Empty means a uniform distribution.
+    /// </summary>
+    public float[] VariantWeights { get; init; } = [];
+
+    /// <summary>Probability, per allele, that a mutation occurs when this gene is passed to a child.</summary>
+    public float MutationChance { get; init; }
+
+    /// <summary>
+    /// The gene's contributions to phenotype traits: trait name → formula. Each formula may use the
+    /// variable <c>value</c> (this gene's expressed phenotype), any other gene's id (its expressed
+    /// value) and any environment variable the caller supplies. Contributions to the same trait
+    /// across genes are summed.
+    /// </summary>
+    public Dictionary<string, string> Effects { get; init; } = new();
+
+    /// <summary>Free-form category tags for grouping genes (used by formula grouping and content tooling).</summary>
+    public string[] Tags { get; init; } = [];
+
+    private IReadOnlyDictionary<string, Formula>? _compiled;
+
+    /// <summary>The <see cref="Effects"/> compiled once into evaluable formulas (lazy, cached).</summary>
+    [JsonIgnore]
+    public IReadOnlyDictionary<string, Formula> CompiledEffects => _compiled ??= CompileEffects();
+
+    private Dictionary<string, Formula> CompileEffects()
+    {
+        var compiled = new Dictionary<string, Formula>(StringComparer.Ordinal);
+        foreach (var (trait, expression) in Effects)
+        {
+            try
+            {
+                compiled[trait] = Formula.Compile(expression);
+            }
+            catch (FormulaException error)
+            {
+                throw new InvalidDataException(
+                    $"Gene '{DefName}' effect on trait '{trait}' has an invalid formula "
+                        + $"\"{expression}\": {error.Message}"
+                );
+            }
+        }
+
+        return compiled;
+    }
+}

src/MrGameEng.Content/Genetics/GeneSampling.cs

@@ -0,0 +1,56 @@
+namespace MrGameEng.Genetics;
+
+/// <summary>
+/// Shared, deterministic allele sampling used by both <see cref="Genome.Generate"/> (gene defaults)
+/// and <see cref="GenomeTemplate"/> (per-individual base overrides). Centralizes the numeric
+/// spread+clamp and the weighted discrete pick so the two paths stay consistent.
+/// </summary>
+internal static class GeneSampling
+{
+    /// <summary>A numeric allele drawn as <c>baseValue ± spread·|baseValue|</c>, clamped to the gene's range.</summary>
+    public static float Numeric(GeneDef gene, float baseValue, float spread, Random random)
+    {
+        var value = baseValue + (random.NextSingle() * 2f - 1f) * spread * MathF.Abs(baseValue);
+        return Math.Clamp(value, gene.Min, gene.Max);
+    }
+
+    /// <summary>
+    /// A discrete variant index in <c>[0, Variants)</c>, picked from <paramref name="weights"/> when
+    /// they match the variant count, otherwise the gene's own weights, otherwise uniformly.
+    /// </summary>
+    public static float Variant(GeneDef gene, float[]? weights, Random random)
+    {
+        var variants = Math.Max(1, gene.Variants);
+        var w =
+            weights is { Length: > 0 } && weights.Length == variants
+                ? weights
+                : gene.VariantWeights;
+        if (w.Length != variants)
+        {
+            return random.Next(variants);
+        }
+
+        var total = 0f;
+        foreach (var value in w)
+        {
+            total += MathF.Max(0f, value);
+        }
+
+        if (total <= 0f)
+        {
+            return random.Next(variants);
+        }
+
+        var roll = random.NextSingle() * total;
+        for (var i = 0; i < variants; i++)
+        {
+            roll -= MathF.Max(0f, w[i]);
+            if (roll < 0f)
+            {
+                return i;
+            }
+        }
+
+        return variants - 1;
+    }
+}

src/MrGameEng.Content/Genetics/Genome.cs

@@ -0,0 +1,156 @@
+namespace MrGameEng.Genetics;
+
+/// <summary>
+/// An individual's managed genome: a variable-composition map from gene id to the
+/// <see cref="Allele"/> pair it carries. Because composition is open, two organisms need not share
+/// the same gene set and a genome can gain "foreign" genes — the basis for arbitrary hybrids. The
+/// genome is generated from a set of <see cref="GeneDef"/>s, bred meiotically with mutation, and
+/// expressed into phenotype values; all randomness flows through a caller-owned seeded
+/// <see cref="Random"/> so the simulation stays deterministic.
+/// </summary>
+public sealed class Genome
+{
+    private readonly Dictionary<string, Allele> _alleles;
+
+    /// <summary>Creates an empty genome.</summary>
+    public Genome() => _alleles = new Dictionary<string, Allele>(StringComparer.Ordinal);
+
+    /// <summary>Creates a genome from an existing allele map (copied).</summary>
+    public Genome(IReadOnlyDictionary<string, Allele> alleles) =>
+        _alleles = new Dictionary<string, Allele>(alleles, StringComparer.Ordinal);
+
+    /// <summary>The carried genes and their allele pairs.</summary>
+    public IReadOnlyDictionary<string, Allele> Alleles => _alleles;
+
+    /// <summary>Whether the genome carries the gene <paramref name="geneId"/>.</summary>
+    public bool Has(string geneId) => _alleles.ContainsKey(geneId);
+
+    /// <summary>Gets or sets the allele pair for <paramref name="geneId"/>.</summary>
+    public Allele this[string geneId]
+    {
+        get => _alleles[geneId];
+        set => _alleles[geneId] = value;
+    }
+
+    /// <summary>Removes a gene from the genome; returns whether it was present.</summary>
+    public bool Remove(string geneId) => _alleles.Remove(geneId);
+
+    /// <summary>
+    /// Expresses the gene's phenotype value: the mean of the alleles for a numeric gene, the
+    /// dominant (lower) allele for a discrete one. Throws if the genome does not carry the gene.
+    /// </summary>
+    public float Express(GeneDef gene)
+    {
+        if (!_alleles.TryGetValue(gene.DefName, out var allele))
+        {
+            throw new KeyNotFoundException($"Genome does not carry gene '{gene.DefName}'.");
+        }
+
+        return gene.Kind == GeneKind.Numeric ? allele.Mean : allele.Dominant;
+    }
+
+    /// <summary>Builds the allele map for serialization (a copy).</summary>
+    public Dictionary<string, Allele> ToDictionary() => new(_alleles, StringComparer.Ordinal);
+
+    /// <summary>
+    /// Generates a fresh genome carrying every gene in <paramref name="genes"/>, each allele drawn
+    /// independently around the gene's default with its spread (numeric) or from its variant
+    /// distribution (discrete).
+    /// </summary>
+    public static Genome Generate(IEnumerable<GeneDef> genes, Random random)
+    {
+        var genome = new Genome();
+        foreach (var gene in genes)
+        {
+            genome._alleles[gene.DefName] = new Allele(
+                GenerateAllele(gene, random),
+                GenerateAllele(gene, random)
+            );
+        }
+
+        return genome;
+    }
+
+    /// <summary>
+    /// Breeds a child genome from two parents (meiosis): the child carries every gene either parent
+    /// has. For a gene both carry, one allele is drawn from each parent; for a gene only one parent
+    /// carries, it is inherited (from that parent, on both sides) with 50% probability. Every
+    /// inherited allele may then mutate per its <see cref="GeneDef"/>. <paramref name="registry"/>
+    /// supplies the def for each gene id; genes absent from it are skipped.
+    /// <paramref name="mutationChance"/>, when given, overrides every gene's
+    /// <see cref="GeneDef.MutationChance"/> — letting the caller drive mutation from an evolvable
+    /// trait rather than a fixed per-gene constant.
+    /// </summary>
+    public static Genome Breed(
+        Genome a,
+        Genome b,
+        IReadOnlyDictionary<string, GeneDef> registry,
+        Random random,
+        float? mutationChance = null
+    )
+    {
+        var child = new Genome();
+        foreach (var geneId in UnionKeys(a, b))
+        {
+            if (!registry.TryGetValue(geneId, out var gene))
+            {
+                continue;
+            }
+
+            var chance = mutationChance ?? gene.MutationChance;
+            var inA = a.Has(geneId);
+            var inB = b.Has(geneId);
+            if (inA && inB)
+            {
+                child._alleles[geneId] = new Allele(
+                    Meiosis(gene, a[geneId], chance, random),
+                    Meiosis(gene, b[geneId], chance, random)
+                );
+            }
+            else if (random.NextSingle() < 0.5f)
+            {
+                var parent = inA ? a : b;
+                child._alleles[geneId] = new Allele(
+                    Meiosis(gene, parent[geneId], chance, random),
+                    Meiosis(gene, parent[geneId], chance, random)
+                );
+            }
+        }
+
+        return child;
+    }
+
+    // One inherited allele: pick one of the parent slot's two alleles, then maybe mutate it.
+    private static float Meiosis(GeneDef gene, Allele parent, float mutationChance, Random random)
+    {
+        var inherited = random.NextSingle() < 0.5f ? parent.A : parent.B;
+        if (random.NextSingle() >= mutationChance)
+        {
+            return inherited;
+        }
+
+        if (gene.Kind == GeneKind.Discrete)
+        {
+            return GeneSampling.Variant(gene, null, random);
+        }
+
+        var shifted =
+            inherited
+            + (random.NextSingle() * 2f - 1f) * gene.MutationMagnitude * MathF.Abs(inherited);
+        return Math.Clamp(shifted, gene.Min, gene.Max);
+    }
+
+    private static float GenerateAllele(GeneDef gene, Random random) =>
+        gene.Kind == GeneKind.Discrete
+            ? GeneSampling.Variant(gene, null, random)
+            : GeneSampling.Numeric(gene, gene.Default, gene.Spread, random);
+
+    // Deterministic union of both parents' gene ids (ordered) so breeding is reproducible.
+    private static IEnumerable<string> UnionKeys(Genome a, Genome b)
+    {
+        var keys = new SortedSet<string>(StringComparer.Ordinal);
+        keys.UnionWith(a._alleles.Keys);
+        keys.UnionWith(b._alleles.Keys);
+        return keys;
+    }
+}

src/MrGameEng.Content/Genetics/GenomeTemplate.cs

@@ -0,0 +1,61 @@
+namespace MrGameEng.Genetics;
+
+/// <summary>
+/// A species' (or any organism kind's) gene allotment: which <see cref="GeneDef"/>s an individual
+/// carries and the per-organism base values its alleles are generated around. The same
+/// <see cref="GeneDef"/> (e.g. "optimal light") is shared by every species, while the template
+/// supplies the species-specific centre and spread — so an oak and grass differ in values, not in
+/// machinery. <see cref="Generate"/> draws a fresh individual; <see cref="Registry"/> feeds breeding
+/// and trait computation.
+/// </summary>
+public sealed class GenomeTemplate
+{
+    /// <summary>
+    /// One gene in the allotment. <paramref name="Base"/>/<paramref name="Spread"/> centre a numeric
+    /// gene's alleles; <paramref name="VariantWeights"/> (optional) override a discrete gene's
+    /// variant distribution for this organism.
+    /// </summary>
+    public readonly record struct Entry(
+        GeneDef Gene,
+        float Base,
+        float Spread,
+        float[]? VariantWeights = null
+    );
+
+    private readonly List<Entry> _entries;
+    private readonly Dictionary<string, GeneDef> _registry;
+
+    /// <summary>Builds a template from its gene entries.</summary>
+    public GenomeTemplate(IEnumerable<Entry> entries)
+    {
+        _entries = entries.ToList();
+        _registry = new Dictionary<string, GeneDef>(StringComparer.Ordinal);
+        foreach (var entry in _entries)
+        {
+            _registry[entry.Gene.DefName] = entry.Gene;
+        }
+    }
+
+    /// <summary>The gene entries that make up the allotment.</summary>
+    public IReadOnlyList<Entry> Entries => _entries;
+
+    /// <summary>Gene id → def for every carried gene; pass to <see cref="Genome.Breed"/> and <see cref="Phenotype.Compute"/>.</summary>
+    public IReadOnlyDictionary<string, GeneDef> Registry => _registry;
+
+    /// <summary>Generates a fresh individual: two alleles per gene drawn around each entry's base/variant.</summary>
+    public Genome Generate(Random random)
+    {
+        var genome = new Genome();
+        foreach (var entry in _entries)
+        {
+            genome[entry.Gene.DefName] = new Allele(Draw(entry, random), Draw(entry, random));
+        }
+
+        return genome;
+    }
+
+    private static float Draw(Entry entry, Random random) =>
+        entry.Gene.Kind == GeneKind.Discrete
+            ? GeneSampling.Variant(entry.Gene, entry.VariantWeights, random)
+            : GeneSampling.Numeric(entry.Gene, entry.Base, entry.Spread, random);
+}

src/MrGameEng.Content/Genetics/Phenotype.cs

@@ -0,0 +1,87 @@
+using MrGameEng.Formulas;
+
+namespace MrGameEng.Genetics;
+
+/// <summary>
+/// Computes the trait layer — the phenotype the simulation actually reads — from a
+/// <see cref="Genome"/>. Each gene's <see cref="GeneDef.Effects"/> formulas are evaluated and their
+/// results summed per trait name, so systems never touch genes directly: one fruiting system reads
+/// a <c>fruitYield</c> trait whether it comes from a tree or a human carrying a "fruit" gene.
+/// Formulas see the variable <c>value</c> (the contributing gene's expressed phenotype), any other
+/// carried gene's id, and whatever environment variables the caller supplies.
+/// </summary>
+public static class Phenotype
+{
+    /// <summary>
+    /// Evaluates every carried gene's effects against the genome and an optional
+    /// <paramref name="environment"/>, summing contributions into a trait map. Genes missing from
+    /// <paramref name="registry"/> are skipped.
+    /// </summary>
+    public static Dictionary<string, float> Compute(
+        Genome genome,
+        IReadOnlyDictionary<string, GeneDef> registry,
+        IFormulaContext? environment = null
+    )
+    {
+        var traits = new Dictionary<string, float>(StringComparer.Ordinal);
+        var context = new GenomeContext(genome, registry, environment);
+        foreach (var geneId in genome.Alleles.Keys)
+        {
+            if (!registry.TryGetValue(geneId, out var gene) || gene.CompiledEffects.Count == 0)
+            {
+                continue;
+            }
+
+            context.Self = genome.Express(gene);
+            foreach (var (trait, formula) in gene.CompiledEffects)
+            {
+                traits[trait] = traits.GetValueOrDefault(trait) + formula.Evaluate(context);
+            }
+        }
+
+        return traits;
+    }
+
+    // Resolves formula variables for a gene effect: 'value' is the current gene's phenotype, any
+    // carried gene's id resolves to its phenotype, anything else falls through to the environment.
+    private sealed class GenomeContext(
+        Genome genome,
+        IReadOnlyDictionary<string, GeneDef> registry,
+        IFormulaContext? environment
+    ) : IFormulaContext
+    {
+        public float Self;
+
+        public float Resolve(string name)
+        {
+            if (name == "value")
+            {
+                return Self;
+            }
+
+            if (genome.Has(name) && registry.TryGetValue(name, out var gene))
+            {
+                return genome.Express(gene);
+            }
+
+            if (environment is not null)
+            {
+                return environment.Resolve(name);
+            }
+
+            throw new FormulaException($"Unknown variable '{name}' while computing traits.");
+        }
+
+        // Группировка генов в формулах: значения всех генов, чьи id подходят под шаблон (gsum/gavg/…).
+        public IEnumerable<float> ResolveMatching(Func<string, bool> matches)
+        {
+            foreach (var geneId in genome.Alleles.Keys)
+            {
+                if (matches(geneId) && registry.TryGetValue(geneId, out var gene))
+                {
+                    yield return genome.Express(gene);
+                }
+            }
+        }
+    }
+}

src/MrGameEng.Content/Mods/DefDatabase.cs

@@ -1,5 +1,6 @@
 using System.Text.Json;
 using System.Text.Json.Nodes;
+using System.Text.RegularExpressions;
 
 namespace MrGameEng.Mods;
 
@@ -24,6 +25,18 @@ public sealed class DefDatabase
     private readonly Dictionary<string, TypeEntry> _byKey = new(StringComparer.OrdinalIgnoreCase);
     private readonly Dictionary<Type, TypeEntry> _byType = [];
 
+    /// <summary>Reserved def-file <c>"type"</c> that carries content patches rather than defs.</summary>
+    public const string PatchTypeKey = "Patch";
+
+    private sealed record PatchRule(string DefType, Regex Match, JsonObject Set);
+
+    private sealed record ValidationRule(string Field, Regex Pattern, string Description);
+
+    private readonly List<PatchRule> _patches = [];
+    private readonly Dictionary<string, List<ValidationRule>> _validators = new(
+        StringComparer.OrdinalIgnoreCase
+    );
+
     private static readonly JsonDocumentOptions DocumentOptions = new()
     {
         CommentHandling = JsonCommentHandling.Skip,
@@ -43,6 +56,38 @@ public sealed class DefDatabase
         _byType.Add(typeof(T), entry);
     }
 
+    /// <summary>
+    /// Registers a load-time validation: the string <paramref name="field"/> of every resolved def of
+    /// type <paramref name="typeKey"/> must match <paramref name="pattern"/> (a regex), or
+    /// <see cref="Load"/> throws. Non-string or absent fields are skipped. Use it to enforce naming
+    /// conventions (e.g. gene ids start with <c>Gene</c>) or key/format rules across a mod's content.
+    /// </summary>
+    public void RegisterValidator(
+        string typeKey,
+        string field,
+        string pattern,
+        string? description = null
+    )
+    {
+        Regex regex;
+        try
+        {
+            regex = new Regex(pattern, RegexOptions.CultureInvariant);
+        }
+        catch (ArgumentException error)
+        {
+            throw new ArgumentException($"Invalid validator regex '{pattern}': {error.Message}");
+        }
+
+        if (!_validators.TryGetValue(typeKey, out var list))
+        {
+            list = [];
+            _validators[typeKey] = list;
+        }
+
+        list.Add(new ValidationRule(field, regex, description ?? $"pattern /{pattern}/"));
+    }
+
     /// <summary>
     /// Loads every <c>Defs/**/*.json</c> of <paramref name="mods"/> (in load order) and
     /// resolves inheritance. Call once after registering all def types.
@@ -66,6 +111,8 @@ public sealed class DefDatabase
             }
         }
 
+        ApplyPatches();
+
         foreach (var entry in _byKey.Values)
         {
             Resolve(entry);
@@ -133,6 +180,12 @@ public sealed class DefDatabase
             ?? throw new InvalidDataException(
                 $"Def file '{file}' (mod '{mod.Id}') has no \"type\" field."
             );
+        if (string.Equals(typeKey, PatchTypeKey, StringComparison.OrdinalIgnoreCase))
+        {
+            LoadPatches(mod, file, root);
+            return;
+        }
+
         if (!_byKey.TryGetValue(typeKey, out var entry))
         {
             throw new InvalidDataException(
@@ -169,8 +222,83 @@ public sealed class DefDatabase
         }
     }
 
-    private static void Resolve(TypeEntry entry)
+    // Парсит файл-патч: операции { defType, match (регэксп по defName), set: {поля} }.
+    private void LoadPatches(Mod mod, string file, JsonNode root)
     {
+        if (root["patches"] is not JsonArray patches)
+        {
+            throw new InvalidDataException(
+                $"Patch file '{file}' (mod '{mod.Id}') has no \"patches\" array."
+            );
+        }
+
+        foreach (var node in patches)
+        {
+            if (node is not JsonObject patch)
+            {
+                throw new InvalidDataException(
+                    $"Patch file '{file}' (mod '{mod.Id}') contains a non-object patch."
+                );
+            }
+
+            var defType =
+                patch["defType"]?.GetValue<string>()
+                ?? throw new InvalidDataException($"A patch in '{file}' has no \"defType\".");
+            var match =
+                patch["match"]?.GetValue<string>()
+                ?? throw new InvalidDataException($"A patch in '{file}' has no \"match\".");
+            if (patch["set"] is not JsonObject set)
+            {
+                throw new InvalidDataException($"A patch in '{file}' has no \"set\" object.");
+            }
+
+            Regex regex;
+            try
+            {
+                regex = new Regex(match, RegexOptions.CultureInvariant);
+            }
+            catch (ArgumentException error)
+            {
+                throw new InvalidDataException(
+                    $"Patch in '{file}' has invalid regex '{match}': {error.Message}"
+                );
+            }
+
+            _patches.Add(new PatchRule(defType, regex, (JsonObject)set.DeepClone()));
+        }
+    }
+
+    // Применяет патчи к сырым дефам (до резолва), в порядке загрузки: каждому дефу нужного типа,
+    // чьё имя подходит под регэксп, проставляются поля set. Поля наследуются детьми как обычно.
+    private void ApplyPatches()
+    {
+        foreach (var patch in _patches)
+        {
+            if (!_byKey.TryGetValue(patch.DefType, out var entry))
+            {
+                throw new InvalidDataException(
+                    $"A patch targets unknown def type '{patch.DefType}'."
+                );
+            }
+
+            foreach (var raw in entry.Raw)
+            {
+                if (!patch.Match.IsMatch(raw.Key))
+                {
+                    continue;
+                }
+
+                foreach (var (key, value) in patch.Set)
+                {
+                    raw.Value[key] = value?.DeepClone();
+                }
+            }
+        }
+    }
+
+    private void Resolve(TypeEntry entry)
+    {
+        _validators.TryGetValue(entry.Key, out var rules);
         foreach (var defName in entry.Raw.Keys.Order(StringComparer.Ordinal))
         {
             var merged = MergeChain(entry, defName, []);
@@ -179,6 +307,11 @@ public sealed class DefDatabase
                 continue;
             }
 
+            if (rules is not null)
+            {
+                Validate(entry.Key, defName, merged, rules);
+            }
+
             var def =
                 (Def?)merged.Deserialize(entry.ClrType, ModInfo.JsonOptions)
                 ?? throw new InvalidDataException(
@@ -188,6 +321,28 @@ public sealed class DefDatabase
         }
     }
 
+    private static void Validate(
+        string typeKey,
+        string defName,
+        JsonObject merged,
+        List<ValidationRule> rules
+    )
+    {
+        foreach (var rule in rules)
+        {
+            if (
+                merged[rule.Field] is JsonValue value
+                && value.TryGetValue<string>(out var text)
+                && !rule.Pattern.IsMatch(text)
+            )
+            {
+                throw new InvalidDataException(
+                    $"Def '{defName}' ({typeKey}) field '{rule.Field}'=\"{text}\" violates {rule.Description}."
+                );
+            }
+        }
+    }
+
     private static JsonObject MergeChain(TypeEntry entry, string defName, HashSet<string> seen)
     {
         if (!seen.Add(defName))

src/MrGameEng.Content/Mods/ModInfo.cs

@@ -1,4 +1,5 @@
 using System.Text.Json;
+using System.Text.Json.Serialization;
 
 namespace MrGameEng.Mods;
 
@@ -14,6 +15,7 @@ public sealed class ModInfo
         ReadCommentHandling = JsonCommentHandling.Skip,
         AllowTrailingCommas = true,
         WriteIndented = true,
+        Converters = { new JsonStringEnumConverter() },
     };
 
     /// <summary>Unique mod id, referenced by <see cref="Dependencies"/> of other mods.</summary>

src/MrGameEng.Core/Calendar.cs

@@ -10,16 +10,21 @@ namespace MrGameEng.Core;
 public sealed class Calendar
 {
     private readonly GameClock _clock;
+    private readonly double _startDay;
     private float _secondsPerDay;
 
     /// <summary>
     /// Creates a calendar reading <paramref name="clock"/>; one day spans
     /// <paramref name="secondsPerDay"/> seconds of scaled time (must be positive).
+    /// <paramref name="startDay"/> offsets the calendar by (fractional) days at clock 0 — e.g.
+    /// <c>7.0 / 24</c> starts the world at 07:00 instead of midnight. It shifts the time of day and
+    /// the day/night phase that reads <see cref="DayProgress"/>, without touching the clock itself.
     /// </summary>
-    public Calendar(GameClock clock, float secondsPerDay)
+    public Calendar(GameClock clock, float secondsPerDay, double startDay = 0.0)
     {
         _clock = clock ?? throw new ArgumentNullException(nameof(clock));
         SecondsPerDay = secondsPerDay;
+        _startDay = startDay;
     }
 
     /// <summary>Scaled seconds per in-game day. Must be positive; raising it slows the calendar.</summary>
@@ -36,8 +41,8 @@ public sealed class Calendar
                     );
     }
 
-    /// <summary>Total elapsed days as a continuous value (e.g. 3.5 = midday of day 4).</summary>
+    /// <summary>Total elapsed days as a continuous value (e.g. 3.5 = midday of day 4), incl. the start offset.</summary>
-    public double TotalDays => _clock.TotalTime / _secondsPerDay;
+    public double TotalDays => _clock.TotalTime / _secondsPerDay + _startDay;
 
     /// <summary>The current day number, counting from 1.</summary>
     public int Day => (int)TotalDays + 1;
@@ -51,6 +56,15 @@ public sealed class Calendar
             return (float)(days - Math.Floor(days));
         }
     }
+
+    /// <summary>Minutes elapsed in the current day, 0–1439 (a day is 24×60 in-game minutes).</summary>
+    public int MinuteOfDay => (int)(DayProgress * 1440f) % 1440;
+
+    /// <summary>Hour of the current day, 0–23.</summary>
+    public int Hour => MinuteOfDay / 60;
+
+    /// <summary>Minute of the current hour, 0–59.</summary>
+    public int Minute => MinuteOfDay % 60;
 }
 
 /// <summary>Wires the in-game calendar into the engine.</summary>
@@ -59,11 +73,16 @@ public static class CalendarEngineExtensions
     /// <summary>
     /// Creates a <see cref="Calendar"/> bound to the context's clock and registers it as a
     /// service. Call once per world. <paramref name="secondsPerDay"/> is the scaled-time length
-    /// of one in-game day (must be positive).
+    /// of one in-game day (must be positive); <paramref name="startDay"/> offsets the starting
+    /// time of day in fractional days (e.g. <c>7.0 / 24</c> begins the world at 07:00).
     /// </summary>
-    public static Calendar UseCalendar(this EngineContext context, float secondsPerDay)
+    public static Calendar UseCalendar(
+        this EngineContext context,
+        float secondsPerDay,
+        double startDay = 0.0
+    )
     {
-        var calendar = new Calendar(context.Clock, secondsPerDay);
+        var calendar = new Calendar(context.Clock, secondsPerDay, startDay);
         context.Services.Add(calendar);
         return calendar;
     }

src/MrGameEng.Core/Climate.cs

@@ -0,0 +1,147 @@
+namespace MrGameEng.Core;
+
+/// <summary>The four seasons, in calendar order from the start of the year.</summary>
+public enum Season
+{
+    /// <summary>First quarter of the year — warming.</summary>
+    Spring,
+
+    /// <summary>Second quarter — warmest.</summary>
+    Summer,
+
+    /// <summary>Third quarter — cooling.</summary>
+    Autumn,
+
+    /// <summary>Last quarter — coldest.</summary>
+    Winter,
+}
+
+/// <summary>
+/// Tuning for <see cref="Climate"/>. A year spans <see cref="DaysPerYear"/> in-game days; temperature
+/// follows a seasonal cosine peaking on <see cref="WarmestDay"/>, plus a daily swing (cooler at night).
+/// </summary>
+public readonly record struct ClimateSettings
+{
+    /// <summary>In-game days in one year (e.g. 60 = four 15-day seasons).</summary>
+    public int DaysPerYear { get; init; }
+
+    /// <summary>Yearly mean temperature.</summary>
+    public float MeanTemperature { get; init; }
+
+    /// <summary>Peak deviation from the mean across the seasons (summer high / winter low).</summary>
+    public float SeasonalAmplitude { get; init; }
+
+    /// <summary>Peak deviation from the seasonal mean across one day (warmer at noon, cooler at night).</summary>
+    public float DailyAmplitude { get; init; }
+
+    /// <summary>Day of the year (0-based) with the highest temperature; defaults to mid-summer.</summary>
+    public int WarmestDay { get; init; }
+
+    /// <summary>
+    /// Day of the year (0-based) that the calendar's day 0 maps to. Shifts the whole seasonal phase
+    /// (season and temperature together) so a world can begin in a chosen part of the year — e.g. a
+    /// warm late spring instead of the cold turn of the year. Defaults to 0 (year begins at day 0).
+    /// </summary>
+    public int StartDayOfYear { get; init; }
+
+    /// <summary>Temperate defaults: a 60-day year, mean 12°, ±14° seasonal, ±5° daily, warmest mid-summer.</summary>
+    public static ClimateSettings Default =>
+        new()
+        {
+            DaysPerYear = 60,
+            MeanTemperature = 12f,
+            SeasonalAmplitude = 14f,
+            DailyAmplitude = 5f,
+            WarmestDay = 22, // ~middle of the summer quarter of a 60-day year
+        };
+}
+
+/// <summary>
+/// Continuous climate layered over <see cref="Calendar"/>: a temperature that varies smoothly with the
+/// season and the time of day, plus the current season and year. The whole curve is derived from the
+/// calendar's elapsed time, so it slows or stops with the game clock. Pure read-side, GPU-free and
+/// deterministic; registered as a service via <see cref="ClimateEngineExtensions.UseClimate"/>.
+/// </summary>
+public sealed class Climate
+{
+    private readonly Calendar _calendar;
+    private readonly ClimateSettings _settings;
+
+    /// <summary>Creates a climate reading <paramref name="calendar"/> with the given <paramref name="settings"/>.</summary>
+    public Climate(Calendar calendar, ClimateSettings settings)
+    {
+        _calendar = calendar ?? throw new ArgumentNullException(nameof(calendar));
+        if (settings.DaysPerYear <= 0)
+        {
+            throw new ArgumentOutOfRangeException(
+                nameof(settings),
+                "Days per year must be positive."
+            );
+        }
+
+        _settings = settings;
+    }
+
+    /// <summary>In-game days per year.</summary>
+    public int DaysPerYear => _settings.DaysPerYear;
+
+    /// <summary>Elapsed days shifted by <see cref="ClimateSettings.StartDayOfYear"/> — the seasonal clock.</summary>
+    private double YearDays => _calendar.TotalDays + _settings.StartDayOfYear;
+
+    /// <summary>Continuous position within the current year in <c>[0, 1)</c>.</summary>
+    public double YearProgress
+    {
+        get
+        {
+            var years = YearDays / _settings.DaysPerYear;
+            return years - Math.Floor(years);
+        }
+    }
+
+    /// <summary>The current year, counting from 1.</summary>
+    public int Year => (int)(YearDays / _settings.DaysPerYear) + 1;
+
+    /// <summary>Day within the current year, 0-based.</summary>
+    public int DayOfYear => (int)(YearProgress * _settings.DaysPerYear);
+
+    /// <summary>The current season, derived from the quarter of the year.</summary>
+    public Season Season => (Season)Math.Clamp((int)(YearProgress * 4.0), 0, 3);
+
+    /// <summary>Current temperature: seasonal cosine peaking on the warmest day, plus a daily swing.</summary>
+    public float Temperature
+    {
+        get
+        {
+            var warmFraction = _settings.WarmestDay / (float)_settings.DaysPerYear;
+            var seasonal =
+                _settings.MeanTemperature
+                + _settings.SeasonalAmplitude
+                    * MathF.Cos(MathF.Tau * ((float)YearProgress - warmFraction));
+            var daily = _settings.DailyAmplitude * (2f * Daylight() - 1f);
+            return seasonal + daily;
+        }
+    }
+
+    // Daytime factor 0..1 (0 at midnight, 1 at noon). Mirrors the day/night curve without a
+    // Graphics dependency — Core owns the daily temperature swing.
+    private float Daylight()
+    {
+        var value = -MathF.Cos(MathF.Tau * _calendar.DayProgress);
+        return value > 0f ? value : 0f;
+    }
+}
+
+/// <summary>Wires the climate model into the engine.</summary>
+public static class ClimateEngineExtensions
+{
+    /// <summary>
+    /// Creates a <see cref="Climate"/> bound to the context's <see cref="Calendar"/> service and
+    /// registers it. Call once per world, after <see cref="CalendarEngineExtensions.UseCalendar"/>.
+    /// </summary>
+    public static Climate UseClimate(this EngineContext context, ClimateSettings settings)
+    {
+        var climate = new Climate(context.Services.Get<Calendar>(), settings);
+        context.Services.Add(climate);
+        return climate;
+    }
+}

src/MrGameEng.Core/EngineContext.cs

@@ -1,10 +1,11 @@
-using Microsoft.Xna.Framework.Graphics;
-
 namespace MrGameEng.Core;
 
 /// <summary>
-/// Root object handed to scenes and systems: time, scene manager, services and graphics device.
+/// Root object handed to scenes and systems: time, scene manager and services.
-/// Created by <see cref="GameHost"/>; can also be created standalone for headless tests.
+/// Created by a host (the MonoGame game host or <see cref="HeadlessHost"/>); can also be
+/// created standalone for unit tests. Platform resources such as the graphics device are
+/// published through <see cref="Services"/> by hosts that have them — the core itself has
+/// no platform dependencies.
 /// </summary>
 public sealed class EngineContext
 {
@@ -17,38 +18,16 @@ public sealed class EngineContext
     /// <summary>Registry of module services (input, audio, assets, …).</summary>
     public ServiceRegistry Services { get; } = new();
 
-    /// <summary>
+    /// <summary>Creates a context. Games normally never create one themselves — the host does.</summary>
-    /// The graphics device. Available once the host is initialized;
-    /// throws when accessed in a headless context (unit tests).
-    /// </summary>
-    public GraphicsDevice GraphicsDevice =>
-        _graphicsDevice
-        ?? throw new InvalidOperationException(
-            "GraphicsDevice is not available (headless context)."
-        );
-
-    /// <summary>True when a graphics device is attached.</summary>
-    public bool HasGraphicsDevice => _graphicsDevice is not null;
-
-    private GraphicsDevice? _graphicsDevice;
-
-    /// <summary>Creates a context. Games normally never create one themselves — <see cref="GameHost"/> does.</summary>
     public EngineContext()
     {
         Scenes = new SceneManager(this);
     }
 
-    internal void AttachGraphicsDevice(GraphicsDevice device) => _graphicsDevice = device;
-
     /// <summary>
-    /// Disposes everything the context owns: registered <see cref="IDisposable"/> services
+    /// Disposes everything the context owns: registered <see cref="IDisposable"/> services.
-    /// and the transition renderer. <paramref name="except"/> (the host itself, also a
+    /// Instances in <paramref name="except"/> (the host itself, platform resources the host
-    /// registered service) is skipped — it is being disposed by the caller already.
+    /// disposes on its own) are skipped. Called by hosts on shutdown.
-    /// Called by <see cref="GameHost.Dispose(bool)"/>.
     /// </summary>
-    internal void DisposeOwnedResources(object except)
+    internal void DisposeOwnedResources(params object[] except) => Services.DisposeServices(except);
-    {
-        Scenes.DisposeRenderer();
-        Services.DisposeServices(except);
-    }
 }

src/MrGameEng.Core/Formulas/Formula.cs

@@ -0,0 +1,60 @@
+namespace MrGameEng.Formulas;
+
+/// <summary>
+/// A compiled arithmetic expression — the keystone of the data-driven gene system. A formula is
+/// parsed once from a string in a def (e.g. a gene effect on a trait) into a delegate tree, then
+/// evaluated many times against an <see cref="IFormulaContext"/> that supplies variable values
+/// (gene values, environment readings, other traits). Evaluation is deterministic and
+/// allocation-free; all the work happens in <see cref="Compile"/>.
+///
+/// <para>Grammar: numbers, variables, the constants <c>pi</c>/<c>tau</c>/<c>e</c>, operators
+/// <c>+ - * / %</c>, comparisons <c>&lt; &gt; &lt;= &gt;= == !=</c>, logical <c>&amp;&amp; || !</c>,
+/// the ternary <c>cond ? a : b</c>, and functions <c>abs sign floor ceil round sqrt exp log sin cos
+/// tan min max pow clamp lerp step</c>. Comparisons and logical operators yield <c>1</c>/<c>0</c>.</para>
+/// </summary>
+public sealed class Formula
+{
+    private static readonly IFormulaContext Empty = new EmptyContext();
+
+    private readonly Func<IFormulaContext, float> _root;
+
+    private Formula(string source, Func<IFormulaContext, float> root)
+    {
+        Source = source;
+        _root = root;
+    }
+
+    /// <summary>The original expression text this formula was compiled from.</summary>
+    public string Source { get; }
+
+    /// <summary>
+    /// Parses and compiles <paramref name="expression"/>. Throws <see cref="FormulaException"/> on any
+    /// lexical or syntactic error, with the offending position.
+    /// </summary>
+    public static Formula Compile(string expression)
+    {
+        ArgumentNullException.ThrowIfNull(expression);
+        var tokens = FormulaLexer.Tokenize(expression);
+        var root = new FormulaParser(tokens).ParseProgram();
+        return new Formula(expression, root);
+    }
+
+    /// <summary>Evaluates the formula, resolving variables through <paramref name="context"/>.</summary>
+    public float Evaluate(IFormulaContext context)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+        return _root(context);
+    }
+
+    /// <summary>
+    /// Evaluates a formula that references no variables. Throws <see cref="FormulaException"/> if it
+    /// turns out to reference one.
+    /// </summary>
+    public float Evaluate() => _root(Empty);
+
+    private sealed class EmptyContext : IFormulaContext
+    {
+        public float Resolve(string name) =>
+            throw new FormulaException($"No context to resolve variable '{name}'.");
+    }
+}

src/MrGameEng.Core/Formulas/FormulaContext.cs

@@ -0,0 +1,35 @@
+namespace MrGameEng.Formulas;
+
+/// <summary>
+/// Supplies variable values to a compiled <see cref="Formula"/>. A context maps a variable name
+/// (a gene value, an environment reading, another trait…) to a number; the formula engine itself
+/// is data-agnostic, so any consumer can back this with whatever lookup it owns.
+/// </summary>
+public interface IFormulaContext
+{
+    /// <summary>
+    /// Returns the value bound to <paramref name="name"/>. Throw (e.g. <see cref="FormulaException"/>)
+    /// if the name is unknown — the engine does not invent a default.
+    /// </summary>
+    float Resolve(string name);
+
+    /// <summary>
+    /// Returns the values of every variable whose name satisfies <paramref name="matches"/> — the
+    /// backing for the group functions (<c>gsum</c>, <c>gavg</c>, …) that aggregate over a name
+    /// pattern, e.g. all <c>leaf_*</c> genes. Contexts with no enumerable variables return nothing.
+    /// </summary>
+    IEnumerable<float> ResolveMatching(Func<string, bool> matches) => [];
+}
+
+/// <summary>An <see cref="IFormulaContext"/> backed by a lookup delegate — handy for tests and ad-hoc use.</summary>
+public sealed class DelegateFormulaContext : IFormulaContext
+{
+    private readonly Func<string, float> _resolve;
+
+    /// <summary>Wraps <paramref name="resolve"/>; it is called once per variable reference per evaluation.</summary>
+    public DelegateFormulaContext(Func<string, float> resolve) =>
+        _resolve = resolve ?? throw new ArgumentNullException(nameof(resolve));
+
+    /// <inheritdoc />
+    public float Resolve(string name) => _resolve(name);
+}

src/MrGameEng.Core/Formulas/FormulaException.cs

@@ -0,0 +1,12 @@
+namespace MrGameEng.Formulas;
+
+/// <summary>
+/// Thrown when a <see cref="Formula"/> cannot be lexed or parsed, or when a compiled formula
+/// references a variable the context cannot resolve at evaluation time.
+/// </summary>
+public sealed class FormulaException : Exception
+{
+    /// <summary>Creates the exception with a human-readable <paramref name="message"/>.</summary>
+    public FormulaException(string message)
+        : base(message) { }
+}

src/MrGameEng.Core/Formulas/FormulaFunctions.cs

@@ -0,0 +1,90 @@
+using Node = System.Func<MrGameEng.Formulas.IFormulaContext, float>;
+
+namespace MrGameEng.Formulas;
+
+/// <summary>
+/// The built-in function set available inside formulas. Each entry validates its argument count at
+/// compile time and returns a <see cref="Node"/> that evaluates its operands then the math. Kept
+/// deterministic and side-effect-free so formulas stay pure.
+/// </summary>
+internal static class FormulaFunctions
+{
+    public static Node Build(string name, List<Node> args)
+    {
+        switch (name)
+        {
+            case "abs":
+                return Unary(name, args, MathF.Abs);
+            case "sign":
+                return Unary(name, args, x => MathF.Sign(x));
+            case "floor":
+                return Unary(name, args, MathF.Floor);
+            case "ceil":
+                return Unary(name, args, MathF.Ceiling);
+            case "round":
+                return Unary(name, args, MathF.Round);
+            case "sqrt":
+                return Unary(name, args, MathF.Sqrt);
+            case "exp":
+                return Unary(name, args, MathF.Exp);
+            case "log":
+                return args.Count == 2
+                    ? Binary(name, args, MathF.Log)
+                    : Unary(name, args, MathF.Log);
+            case "sin":
+                return Unary(name, args, MathF.Sin);
+            case "cos":
+                return Unary(name, args, MathF.Cos);
+            case "tan":
+                return Unary(name, args, MathF.Tan);
+            case "min":
+                return Binary(name, args, MathF.Min);
+            case "max":
+                return Binary(name, args, MathF.Max);
+            case "pow":
+                return Binary(name, args, MathF.Pow);
+            case "clamp":
+                return Ternary(name, args, (x, lo, hi) => Math.Clamp(x, lo, hi));
+            case "lerp":
+                return Ternary(name, args, (a, b, t) => a + (b - a) * t);
+            case "step":
+                return Binary(name, args, (edge, x) => x < edge ? 0f : 1f);
+            default:
+                throw new FormulaException($"Unknown function '{name}'.");
+        }
+    }
+
+    private static Node Unary(string name, List<Node> args, Func<float, float> op)
+    {
+        Require(name, args, 1);
+        var a = args[0];
+        return ctx => op(a(ctx));
+    }
+
+    private static Node Binary(string name, List<Node> args, Func<float, float, float> op)
+    {
+        Require(name, args, 2);
+        var a = args[0];
+        var b = args[1];
+        return ctx => op(a(ctx), b(ctx));
+    }
+
+    private static Node Ternary(string name, List<Node> args, Func<float, float, float, float> op)
+    {
+        Require(name, args, 3);
+        var a = args[0];
+        var b = args[1];
+        var c = args[2];
+        return ctx => op(a(ctx), b(ctx), c(ctx));
+    }
+
+    private static void Require(string name, List<Node> args, int count)
+    {
+        if (args.Count != count)
+        {
+            throw new FormulaException(
+                $"Function '{name}' expects {count} argument(s) but got {args.Count}."
+            );
+        }
+    }
+}

src/MrGameEng.Core/Formulas/FormulaGroups.cs

@@ -0,0 +1,98 @@
+using System.Text.RegularExpressions;
+using Node = System.Func<MrGameEng.Formulas.IFormulaContext, float>;
+
+namespace MrGameEng.Formulas;
+
+/// <summary>
+/// The group functions — <c>gsum</c>, <c>gcount</c>, <c>gavg</c>, <c>gmin</c>, <c>gmax</c> — which
+/// aggregate over every context variable whose name matches a regex literal, e.g.
+/// <c>gsum('leaf_.*')</c> sums all <c>leaf_*</c> genes. The pattern is a string literal compiled to a
+/// <see cref="Regex"/> once at parse time; aggregation reads <see cref="IFormulaContext.ResolveMatching"/>.
+/// </summary>
+internal static class FormulaGroups
+{
+    private static readonly HashSet<string> Names = new(StringComparer.Ordinal)
+    {
+        "gsum",
+        "gcount",
+        "gavg",
+        "gmin",
+        "gmax",
+    };
+
+    public static bool IsGroupFunction(string name) => Names.Contains(name);
+
+    public static Node Build(string name, string pattern)
+    {
+        Regex regex;
+        try
+        {
+            regex = new Regex(pattern, RegexOptions.CultureInvariant);
+        }
+        catch (ArgumentException error)
+        {
+            throw new FormulaException($"Invalid regex '{pattern}': {error.Message}");
+        }
+
+        bool Match(string variable) => regex.IsMatch(variable);
+        return name switch
+        {
+            "gsum" => ctx => Aggregate(ctx.ResolveMatching(Match), sum: true),
+            "gavg" => ctx => Aggregate(ctx.ResolveMatching(Match), average: true),
+            "gcount" => ctx => Count(ctx.ResolveMatching(Match)),
+            "gmin" => ctx => Extreme(ctx.ResolveMatching(Match), max: false),
+            "gmax" => ctx => Extreme(ctx.ResolveMatching(Match), max: true),
+            _ => throw new FormulaException($"Unknown group function '{name}'."),
+        };
+    }
+
+    private static float Aggregate(
+        IEnumerable<float> values,
+        bool sum = false,
+        bool average = false
+    )
+    {
+        var total = 0f;
+        var count = 0;
+        foreach (var value in values)
+        {
+            total += value;
+            count++;
+        }
+
+        if (average)
+        {
+            return count == 0 ? 0f : total / count;
+        }
+
+        return total; // sum (count==0 → 0)
+    }
+
+    private static float Count(IEnumerable<float> values)
+    {
+        var count = 0;
+        foreach (var _ in values)
+        {
+            count++;
+        }
+
+        return count;
+    }
+
+    private static float Extreme(IEnumerable<float> values, bool max)
+    {
+        var has = false;
+        var best = 0f;
+        foreach (var value in values)
+        {
+            if (!has || (max ? value > best : value < best))
+            {
+                best = value;
+            }
+
+            has = true;
+        }
+
+        return best; // empty → 0
+    }
+}

src/MrGameEng.Core/Formulas/FormulaLexer.cs

@@ -0,0 +1,239 @@
+using System.Globalization;
+
+namespace MrGameEng.Formulas;
+
+internal enum TokenType
+{
+    Number,
+    Identifier,
+    String,
+    Plus,
+    Minus,
+    Star,
+    Slash,
+    Percent,
+    LParen,
+    RParen,
+    Comma,
+    Less,
+    Greater,
+    LessEqual,
+    GreaterEqual,
+    EqualEqual,
+    NotEqual,
+    And,
+    Or,
+    Not,
+    Question,
+    Colon,
+    End,
+}
+
+internal readonly struct Token(TokenType type, int position, float number = 0f, string text = "")
+{
+    public TokenType Type { get; } = type;
+    public int Position { get; } = position;
+    public float Number { get; } = number;
+    public string Text { get; } = text;
+}
+
+/// <summary>
+/// Turns a formula string into a flat token list. Pure and allocation-light; recognizes numbers,
+/// identifiers, the arithmetic/comparison/logical operators and the punctuation the parser needs.
+/// </summary>
+internal static class FormulaLexer
+{
+    public static List<Token> Tokenize(string source)
+    {
+        var tokens = new List<Token>();
+        var i = 0;
+        while (i < source.Length)
+        {
+            var c = source[i];
+            if (char.IsWhiteSpace(c))
+            {
+                i++;
+                continue;
+            }
+
+            if (
+                char.IsDigit(c)
+                || (c == '.' && i + 1 < source.Length && char.IsDigit(source[i + 1]))
+            )
+            {
+                var start = i;
+                while (i < source.Length && (char.IsDigit(source[i]) || source[i] == '.'))
+                {
+                    i++;
+                }
+
+                var span = source.AsSpan(start, i - start);
+                if (
+                    !float.TryParse(
+                        span,
+                        NumberStyles.Float,
+                        CultureInfo.InvariantCulture,
+                        out var value
+                    )
+                )
+                {
+                    throw new FormulaException(
+                        $"Invalid number '{span.ToString()}' at position {start}."
+                    );
+                }
+
+                tokens.Add(new Token(TokenType.Number, start, value));
+                continue;
+            }
+
+            if (char.IsLetter(c) || c == '_')
+            {
+                var start = i;
+                while (i < source.Length && (char.IsLetterOrDigit(source[i]) || source[i] == '_'))
+                {
+                    i++;
+                }
+
+                tokens.Add(
+                    new Token(TokenType.Identifier, start, text: source.Substring(start, i - start))
+                );
+                continue;
+            }
+
+            if (c == '\'')
+            {
+                var open = i;
+                var start = ++i;
+                while (i < source.Length && source[i] != '\'')
+                {
+                    i++;
+                }
+
+                if (i >= source.Length)
+                {
+                    throw new FormulaException($"Unterminated string at position {open}.");
+                }
+
+                tokens.Add(
+                    new Token(TokenType.String, open, text: source.Substring(start, i - start))
+                );
+                i++; // пропускаем закрывающую кавычку
+                continue;
+            }
+
+            var pos = i;
+            switch (c)
+            {
+                case '+':
+                    tokens.Add(new Token(TokenType.Plus, pos));
+                    i++;
+                    break;
+                case '-':
+                    tokens.Add(new Token(TokenType.Minus, pos));
+                    i++;
+                    break;
+                case '*':
+                    tokens.Add(new Token(TokenType.Star, pos));
+                    i++;
+                    break;
+                case '/':
+                    tokens.Add(new Token(TokenType.Slash, pos));
+                    i++;
+                    break;
+                case '%':
+                    tokens.Add(new Token(TokenType.Percent, pos));
+                    i++;
+                    break;
+                case '(':
+                    tokens.Add(new Token(TokenType.LParen, pos));
+                    i++;
+                    break;
+                case ')':
+                    tokens.Add(new Token(TokenType.RParen, pos));
+                    i++;
+                    break;
+                case ',':
+                    tokens.Add(new Token(TokenType.Comma, pos));
+                    i++;
+                    break;
+                case '?':
+                    tokens.Add(new Token(TokenType.Question, pos));
+                    i++;
+                    break;
+                case ':':
+                    tokens.Add(new Token(TokenType.Colon, pos));
+                    i++;
+                    break;
+                case '<':
+                    i = AddMaybeEqual(tokens, source, i, TokenType.LessEqual, TokenType.Less);
+                    break;
+                case '>':
+                    i = AddMaybeEqual(tokens, source, i, TokenType.GreaterEqual, TokenType.Greater);
+                    break;
+                case '=':
+                    if (Next(source, i) == '=')
+                    {
+                        tokens.Add(new Token(TokenType.EqualEqual, pos));
+                        i += 2;
+                        break;
+                    }
+
+                    throw new FormulaException($"Expected '==' at position {pos}.");
+                case '!':
+                    if (Next(source, i) == '=')
+                    {
+                        tokens.Add(new Token(TokenType.NotEqual, pos));
+                        i += 2;
+                        break;
+                    }
+
+                    tokens.Add(new Token(TokenType.Not, pos));
+                    i++;
+                    break;
+                case '&':
+                    if (Next(source, i) == '&')
+                    {
+                        tokens.Add(new Token(TokenType.And, pos));
+                        i += 2;
+                        break;
+                    }
+
+                    throw new FormulaException($"Expected '&&' at position {pos}.");
+                case '|':
+                    if (Next(source, i) == '|')
+                    {
+                        tokens.Add(new Token(TokenType.Or, pos));
+                        i += 2;
+                        break;
+                    }
+
+                    throw new FormulaException($"Expected '||' at position {pos}.");
+                default:
+                    throw new FormulaException($"Unexpected character '{c}' at position {pos}.");
+            }
+        }
+
+        tokens.Add(new Token(TokenType.End, source.Length));
+        return tokens;
+    }
+
+    private static int AddMaybeEqual(
+        List<Token> tokens,
+        string source,
+        int i,
+        TokenType withEqual,
+        TokenType plain
+    )
+    {
+        if (Next(source, i) == '=')
+        {
+            tokens.Add(new Token(withEqual, i));
+            return i + 2;
+        }
+
+        tokens.Add(new Token(plain, i));
+        return i + 1;
+    }
+
+    private static char Next(string source, int i) => i + 1 < source.Length ? source[i + 1] : '\0';
+}

src/MrGameEng.Core/Formulas/FormulaParser.cs

@@ -0,0 +1,287 @@
+using Node = System.Func<MrGameEng.Formulas.IFormulaContext, float>;
+
+namespace MrGameEng.Formulas;
+
+/// <summary>
+/// Recursive-descent parser that compiles a token list straight into a tree of <see cref="Node"/>
+/// delegates. Parsing (and therefore all closure allocation) happens once; evaluating the returned
+/// node is allocation-free. Precedence, low to high: ternary, <c>||</c>, <c>&amp;&amp;</c>, equality,
+/// comparison, additive, multiplicative, unary, primary.
+/// </summary>
+internal sealed class FormulaParser(List<Token> tokens)
+{
+    private const float True = 1f;
+    private const float False = 0f;
+
+    private int _pos;
+
+    public Node ParseProgram()
+    {
+        var node = ParseTernary();
+        Expect(TokenType.End);
+        return node;
+    }
+
+    private Node ParseTernary()
+    {
+        var condition = ParseOr();
+        if (!Match(TokenType.Question))
+        {
+            return condition;
+        }
+
+        var whenTrue = ParseTernary();
+        Expect(TokenType.Colon);
+        var whenFalse = ParseTernary();
+        return ctx => condition(ctx) != False ? whenTrue(ctx) : whenFalse(ctx);
+    }
+
+    private Node ParseOr()
+    {
+        var left = ParseAnd();
+        while (Match(TokenType.Or))
+        {
+            var right = ParseAnd();
+            var l = left;
+            left = ctx => l(ctx) != False || right(ctx) != False ? True : False;
+        }
+
+        return left;
+    }
+
+    private Node ParseAnd()
+    {
+        var left = ParseEquality();
+        while (Match(TokenType.And))
+        {
+            var right = ParseEquality();
+            var l = left;
+            left = ctx => l(ctx) != False && right(ctx) != False ? True : False;
+        }
+
+        return left;
+    }
+
+    private Node ParseEquality()
+    {
+        var left = ParseComparison();
+        while (true)
+        {
+            if (Match(TokenType.EqualEqual))
+            {
+                var right = ParseComparison();
+                var l = left;
+                left = ctx => l(ctx) == right(ctx) ? True : False;
+            }
+            else if (Match(TokenType.NotEqual))
+            {
+                var right = ParseComparison();
+                var l = left;
+                left = ctx => l(ctx) != right(ctx) ? True : False;
+            }
+            else
+            {
+                return left;
+            }
+        }
+    }
+
+    private Node ParseComparison()
+    {
+        var left = ParseAdditive();
+        while (true)
+        {
+            if (Match(TokenType.Less))
+            {
+                left = Compare(left, ParseAdditive(), (a, b) => a < b);
+            }
+            else if (Match(TokenType.LessEqual))
+            {
+                left = Compare(left, ParseAdditive(), (a, b) => a <= b);
+            }
+            else if (Match(TokenType.Greater))
+            {
+                left = Compare(left, ParseAdditive(), (a, b) => a > b);
+            }
+            else if (Match(TokenType.GreaterEqual))
+            {
+                left = Compare(left, ParseAdditive(), (a, b) => a >= b);
+            }
+            else
+            {
+                return left;
+            }
+        }
+    }
+
+    private Node ParseAdditive()
+    {
+        var left = ParseMultiplicative();
+        while (true)
+        {
+            if (Match(TokenType.Plus))
+            {
+                var right = ParseMultiplicative();
+                var l = left;
+                left = ctx => l(ctx) + right(ctx);
+            }
+            else if (Match(TokenType.Minus))
+            {
+                var right = ParseMultiplicative();
+                var l = left;
+                left = ctx => l(ctx) - right(ctx);
+            }
+            else
+            {
+                return left;
+            }
+        }
+    }
+
+    private Node ParseMultiplicative()
+    {
+        var left = ParseUnary();
+        while (true)
+        {
+            if (Match(TokenType.Star))
+            {
+                var right = ParseUnary();
+                var l = left;
+                left = ctx => l(ctx) * right(ctx);
+            }
+            else if (Match(TokenType.Slash))
+            {
+                var right = ParseUnary();
+                var l = left;
+                left = ctx => l(ctx) / right(ctx);
+            }
+            else if (Match(TokenType.Percent))
+            {
+                var right = ParseUnary();
+                var l = left;
+                left = ctx => l(ctx) % right(ctx);
+            }
+            else
+            {
+                return left;
+            }
+        }
+    }
+
+    private Node ParseUnary()
+    {
+        if (Match(TokenType.Minus))
+        {
+            var operand = ParseUnary();
+            return ctx => -operand(ctx);
+        }
+
+        if (Match(TokenType.Plus))
+        {
+            return ParseUnary();
+        }
+
+        if (Match(TokenType.Not))
+        {
+            var operand = ParseUnary();
+            return ctx => operand(ctx) != False ? False : True;
+        }
+
+        return ParsePrimary();
+    }
+
+    private Node ParsePrimary()
+    {
+        var token = Current;
+        if (Match(TokenType.Number))
+        {
+            var value = token.Number;
+            return _ => value;
+        }
+
+        if (Match(TokenType.LParen))
+        {
+            var inner = ParseTernary();
+            Expect(TokenType.RParen);
+            return inner;
+        }
+
+        if (Match(TokenType.Identifier))
+        {
+            return Peek(TokenType.LParen) ? ParseCall(token.Text) : ParseName(token.Text);
+        }
+
+        throw new FormulaException($"Unexpected token at position {token.Position}.");
+    }
+
+    private Node ParseName(string name)
+    {
+        switch (name)
+        {
+            case "pi":
+                return _ => MathF.PI;
+            case "tau":
+                return _ => MathF.Tau;
+            case "e":
+                return _ => MathF.E;
+            default:
+                return ctx => ctx.Resolve(name);
+        }
+    }
+
+    private Node ParseCall(string name)
+    {
+        Expect(TokenType.LParen);
+        if (FormulaGroups.IsGroupFunction(name))
+        {
+            var pattern = Current;
+            if (!Match(TokenType.String))
+            {
+                throw new FormulaException(
+                    $"Group function '{name}' expects a quoted regex pattern at position {pattern.Position}."
+                );
+            }
+
+            Expect(TokenType.RParen);
+            return FormulaGroups.Build(name, pattern.Text);
+        }
+
+        var args = new List<Node>();
+        if (!Peek(TokenType.RParen))
+        {
+            do
+            {
+                args.Add(ParseTernary());
+            } while (Match(TokenType.Comma));
+        }
+
+        Expect(TokenType.RParen);
+        return FormulaFunctions.Build(name, args);
+    }
+
+    private static Node Compare(Node left, Node right, Func<float, float, bool> op) =>
+        ctx => op(left(ctx), right(ctx)) ? True : False;
+
+    private Token Current => tokens[_pos];
+
+    private bool Peek(TokenType type) => Current.Type == type;
+
+    private bool Match(TokenType type)
+    {
+        if (Current.Type != type)
+        {
+            return false;
+        }
+
+        _pos++;
+        return true;
+    }
+
+    private void Expect(TokenType type)
+    {
+        if (!Match(type))
+        {
+            throw new FormulaException($"Expected {type} at position {Current.Position}.");
+        }
+    }
+}

src/MrGameEng.Core/GameClock.cs

@@ -2,7 +2,7 @@ namespace MrGameEng.Core;
 
 /// <summary>
 /// Engine time service: per-frame delta, total elapsed time, time scaling and frame counter.
-/// Advanced once per frame by <see cref="GameHost"/>.
+/// Advanced once per frame (or per fixed tick) by the host.
 /// </summary>
 public sealed class GameClock
 {

src/MrGameEng.Core/HeadlessHost.cs

@@ -0,0 +1,107 @@
+using System.Diagnostics;
+
+namespace MrGameEng.Core;
+
+/// <summary>
+/// A game-loop host without a window, GPU or any platform dependency: drives the active
+/// scene's update phase on a fixed timestep. Suits dedicated servers, batch simulation and
+/// tests. Scenes still own draw systems — they are simply never run, and platform services
+/// (graphics device, window) are absent from <see cref="EngineContext.Services"/>, so only
+/// platform-free modules can be used. The fixed step makes simulation time independent of
+/// wall-clock jitter: N ticks always advance the world by exactly N ×
+/// <see cref="FixedDeltaTime"/> seconds.
+/// </summary>
+public sealed class HeadlessHost : IDisposable
+{
+    /// <summary>Engine context shared with scenes and systems.</summary>
+    public EngineContext Context { get; } = new();
+
+    /// <summary>Fixed simulation step in seconds: 1 / <see cref="HeadlessHostOptions.TicksPerSecond"/>.</summary>
+    public float FixedDeltaTime { get; }
+
+    /// <summary>Ticks completed since the host was created.</summary>
+    public long TickCount => Context.Clock.FrameCount;
+
+    // Отстав сильнее этого, Run ресинкается с настоящим временем вместо лавины тиков.
+    private const double MaxLagSeconds = 1.0;
+
+    private readonly HeadlessHostOptions _options;
+
+    /// <summary>Creates a host that starts with <paramref name="initialScene"/>. The scene
+    /// loads on the first tick, mirroring the windowed host's deferred switch.</summary>
+    public HeadlessHost(HeadlessHostOptions options, Scene initialScene)
+    {
+        if (options.TicksPerSecond <= 0f)
+        {
+            throw new ArgumentOutOfRangeException(
+                nameof(options),
+                "TicksPerSecond must be positive."
+            );
+        }
+
+        _options = options;
+        FixedDeltaTime = 1f / options.TicksPerSecond;
+        Context.Scenes.Switch(initialScene);
+    }
+
+    /// <summary>Advances the world by exactly one fixed tick.</summary>
+    public void Tick()
+    {
+        Context.Clock.Advance(FixedDeltaTime);
+        Context.Scenes.Update(Context.Clock);
+    }
+
+    /// <summary>Advances the world by <paramref name="count"/> ticks as fast as possible.</summary>
+    public void RunTicks(long count)
+    {
+        for (long i = 0; i < count; i++)
+        {
+            Tick();
+        }
+    }
+
+    /// <summary>
+    /// Runs until <paramref name="cancellationToken"/> is cancelled. With
+    /// <see cref="HeadlessHostOptions.Realtime"/> ticks are paced to the wall clock — the
+    /// loop sleeps when ahead and, having fallen more than a second behind, resyncs instead
+    /// of bursting a catch-up avalanche. Pacing relies on <see cref="Thread.Sleep(TimeSpan)"/>
+    /// and is accurate to a few milliseconds, not exact.
+    /// </summary>
+    public void Run(CancellationToken cancellationToken = default)
+    {
+        if (!_options.Realtime)
+        {
+            while (!cancellationToken.IsCancellationRequested)
+            {
+                Tick();
+            }
+
+            return;
+        }
+
+        var wallClock = Stopwatch.StartNew();
+        var nextTickAt = 0.0;
+        while (!cancellationToken.IsCancellationRequested)
+        {
+            Tick();
+            nextTickAt += FixedDeltaTime;
+            var ahead = nextTickAt - wallClock.Elapsed.TotalSeconds;
+            if (ahead > 0)
+            {
+                Thread.Sleep(TimeSpan.FromSeconds(ahead));
+            }
+            else if (-ahead > MaxLagSeconds)
+            {
+                nextTickAt = wallClock.Elapsed.TotalSeconds;
+            }
+        }
+    }
+
+    /// <summary>Unloads the active scene and disposes context-owned services.</summary>
+    public void Dispose()
+    {
+        Context.Scenes.Switch(null);
+        Context.Scenes.ApplyPending();
+        Context.DisposeOwnedResources();
+    }
+}

src/MrGameEng.Core/HeadlessHostOptions.cs

@@ -0,0 +1,15 @@
+namespace MrGameEng.Core;
+
+/// <summary>Loop settings for <see cref="HeadlessHost"/>.</summary>
+public sealed class HeadlessHostOptions
+{
+    /// <summary>Fixed simulation rate in ticks per second. Must be positive.</summary>
+    public float TicksPerSecond { get; set; } = 60f;
+
+    /// <summary>
+    /// When true, <see cref="HeadlessHost.Run"/> paces ticks to the wall clock (a dedicated
+    /// server); when false it runs flat out (batch simulation). <see cref="HeadlessHost.RunTicks"/>
+    /// always runs flat out regardless of this setting.
+    /// </summary>
+    public bool Realtime { get; set; } = true;
+}

src/MrGameEng.Core/MrGameEng.Core.csproj

@@ -4,11 +4,11 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="MonoGame.Framework.DesktopGL" />
     <PackageReference Include="Friflo.Engine.ECS" />
   </ItemGroup>
 
   <ItemGroup>
     <InternalsVisibleTo Include="MrGameEng.Core.Tests" />
+    <InternalsVisibleTo Include="MrGameEng.Host" />
   </ItemGroup>
 </Project>

src/MrGameEng.Core/SceneManager.cs

@@ -22,13 +22,24 @@ public sealed class SceneManager
     /// <summary>True while a transition is covering or revealing.</summary>
     public bool IsTransitioning => _state != State.Idle;
 
+    /// <summary>The transition currently covering or revealing, or null while idle.
+    /// Hosts that render overlays read this together with <see cref="TransitionCoverage"/>
+    /// and <see cref="TransitionPhase"/> during their draw phase.</summary>
+    public Transition? ActiveTransition => _state == State.Idle ? null : _transition;
+
+    /// <summary>Coverage of the active transition: 0 = scene fully visible, 1 = fully covered.</summary>
+    public float TransitionCoverage => Math.Clamp(_coverage, 0f, 1f);
+
+    /// <summary>Phase of the active transition. Meaningful only while <see cref="IsTransitioning"/>.</summary>
+    public TransitionPhase TransitionPhase =>
+        _state == State.CoveringOut ? TransitionPhase.Out : TransitionPhase.In;
+
     private readonly EngineContext _context;
     private Scene? _pending;
     private bool _hasPending;
     private Transition? _transition;
     private State _state;
     private float _coverage;
-    private TransitionRenderer? _renderer;
 
     internal SceneManager(EngineContext context) => _context = context;
 
@@ -100,27 +111,9 @@ public sealed class SceneManager
         Current?.Update(clock);
     }
 
-    /// <summary>Draws the active scene and the transition overlay on top. Called by the host.</summary>
+    /// <summary>Draws the active scene. Transition overlays are rendered by the host on top,
-    public void Draw(GameClock clock)
+    /// from <see cref="ActiveTransition"/> and <see cref="TransitionCoverage"/>.</summary>
-    {
+    public void Draw(GameClock clock) => Current?.Draw(clock);
-        Current?.Draw(clock);
-
-        if (_state == State.Idle || !_context.HasGraphicsDevice)
-        {
-            return;
-        }
-
-        _renderer ??= new TransitionRenderer(_context.GraphicsDevice);
-        var phase = _state == State.CoveringOut ? TransitionPhase.Out : TransitionPhase.In;
-        _transition!.Draw(_renderer, Math.Clamp(_coverage, 0f, 1f), phase);
-    }
-
-    /// <summary>Disposes the lazily created transition renderer. Called on host shutdown.</summary>
-    internal void DisposeRenderer()
-    {
-        _renderer?.Dispose();
-        _renderer = null;
-    }
 
     internal void ApplyPending()
     {

src/MrGameEng.Core/ServiceRegistry.cs

@@ -40,16 +40,17 @@ public sealed class ServiceRegistry
 
     /// <summary>
     /// Disposes every registered <see cref="IDisposable"/> service (each instance once, even
-    /// when registered under several types) and clears the registry. <paramref name="except"/>
+    /// when registered under several types) and clears the registry. Instances in
-    /// is skipped. Called on host shutdown.
+    /// <paramref name="except"/> are skipped. Called on host shutdown.
     /// </summary>
-    internal void DisposeServices(object? except = null)
+    internal void DisposeServices(params object[] except)
     {
+        var skipped = new HashSet<object>(except, ReferenceEqualityComparer.Instance);
         var disposed = new HashSet<object>(ReferenceEqualityComparer.Instance);
         foreach (var service in _services.Values)
         {
             if (
-                !ReferenceEquals(service, except)
+                !skipped.Contains(service)
                 && service is IDisposable disposable
                 && disposed.Add(service)
             )

src/MrGameEng.Core/Transition.cs

@@ -1,5 +1,3 @@
-using Microsoft.Xna.Framework;
-
 namespace MrGameEng.Core;
 
 /// <summary>Phase of a scene transition.</summary>
@@ -13,10 +11,12 @@ public enum TransitionPhase
 }
 
 /// <summary>
-/// Visual transition between scenes. The scene switch itself happens at full coverage,
+/// Timing of a visual transition between scenes. The scene switch itself happens at full
-/// so a slow <c>OnLoad</c> of the next scene is hidden behind the overlay.
+/// coverage, so a slow <c>OnLoad</c> of the next scene is hidden behind the overlay.
-/// Transitions are stateless and reusable; progress is tracked by <see cref="SceneManager"/>.
+/// Progress is tracked by <see cref="SceneManager"/> on unscaled time, so transitions work
-/// Runs on unscaled time, so it works while gameplay is paused.
+/// while gameplay is paused. The core only times the phases — how the overlay looks is
+/// defined by the host (the MonoGame host's <c>OverlayTransition</c> and the
+/// <c>Transitions</c> factories); headless hosts simply let transitions pass invisibly.
 /// </summary>
 public abstract class Transition
 {
@@ -32,49 +32,4 @@ public abstract class Transition
         OutDuration = Math.Max(0f, outDuration);
         InDuration = Math.Max(0f, inDuration);
     }
-
-    /// <summary>
-    /// Draws the overlay. <paramref name="coverage"/> is 0 (scene fully visible) to
-    /// 1 (scene fully covered); <paramref name="phase"/> tells which side of the switch this is.
-    /// </summary>
-    public abstract void Draw(TransitionRenderer renderer, float coverage, TransitionPhase phase);
-
-    /// <summary>Fade through a solid color (black by default). Total duration is split between out and in.</summary>
-    public static Transition Fade(float duration = 0.6f, Color? color = null) =>
-        new FadeTransition(duration / 2f, duration / 2f, color ?? Color.Black);
-
-    /// <summary>A curtain wiping across the screen (black by default). Total duration is split between out and in.</summary>
-    public static Transition Wipe(float duration = 0.6f, Color? color = null) =>
-        new WipeTransition(duration / 2f, duration / 2f, color ?? Color.Black);
-
-    private sealed class FadeTransition(float outDuration, float inDuration, Color color)
-        : Transition(outDuration, inDuration)
-    {
-        public override void Draw(
-            TransitionRenderer renderer,
-            float coverage,
-            TransitionPhase phase
-        ) => renderer.Fill(0f, 0f, 1f, 1f, color, coverage);
-    }
-
-    private sealed class WipeTransition(float outDuration, float inDuration, Color color)
-        : Transition(outDuration, inDuration)
-    {
-        public override void Draw(
-            TransitionRenderer renderer,
-            float coverage,
-            TransitionPhase phase
-        )
-        {
-            // Out: шторка растёт слева направо; In: уезжает дальше вправо.
-            if (phase == TransitionPhase.Out)
-            {
-                renderer.Fill(0f, 0f, coverage, 1f, color);
-            }
-            else
-            {
-                renderer.Fill(1f - coverage, 0f, coverage, 1f, color);
-            }
-        }
-    }
 }

src/MrGameEng.Graphics/CameraMath.cs

@@ -33,6 +33,15 @@ public readonly struct CameraState
     /// <summary>Physical-screen to virtual-pixel mapping.</summary>
     public required ViewportMapping Mapping { get; init; }
 
+    /// <summary>
+    /// World point at the centre of the virtual screen — the camera's <em>effective</em> position
+    /// after bounds-clamping, i.e. what the view is actually built around. Prefer this over the raw
+    /// <see cref="Camera.Position"/> when anchoring zoom-to-cursor, so the reposition matches what is
+    /// rendered even while the camera is clamped against <see cref="Camera.Bounds"/>.
+    /// </summary>
+    public Vector2 WorldCenter =>
+        Vector2.Transform(new Vector2(VirtualWidth / 2f, VirtualHeight / 2f), InverseView);
+
     /// <summary>Converts a physical screen point to world coordinates.</summary>
     public Vector2 ScreenToWorld(Vector2 screen)
     {

src/MrGameEng.Graphics/EngineContextGraphicsExtensions.cs

@@ -0,0 +1,19 @@
+using Microsoft.Xna.Framework.Graphics;
+using MrGameEng.Core;
+
+namespace MrGameEng.Graphics;
+
+/// <summary>Graphics-side accessors for the platform-free <see cref="EngineContext"/>.</summary>
+public static class EngineContextGraphicsExtensions
+{
+    /// <summary>
+    /// Returns the <see cref="GraphicsDevice"/> service published by a windowed host.
+    /// Throws in a headless context, where no graphics device exists.
+    /// </summary>
+    public static GraphicsDevice GetGraphicsDevice(this EngineContext context) =>
+        context.Services.GetOrDefault<GraphicsDevice>()
+        ?? throw new InvalidOperationException(
+            "GraphicsDevice is not available: no windowed host has published it "
+                + "(headless context, or graphics are not initialized yet)."
+        );
+}

src/MrGameEng.Graphics/Lighting/DayNight.cs

@@ -0,0 +1,86 @@
+using Microsoft.Xna.Framework;
+using MrGameEng.Core;
+
+namespace MrGameEng.Lighting;
+
+/// <summary>Colors for the day/night ambient: the tint at deep night and at midday.</summary>
+public readonly record struct DayNightSettings
+{
+    /// <summary>Ambient tint at midnight (a dim, cool night).</summary>
+    public Color NightColor { get; init; }
+
+    /// <summary>Ambient tint at noon (white = no tint).</summary>
+    public Color DayColor { get; init; }
+
+    /// <summary>Sensible defaults: a dim blue night, untinted day.</summary>
+    public static DayNightSettings Default =>
+        new() { NightColor = new Color(45, 55, 95), DayColor = Color.White };
+}
+
+/// <summary>
+/// Day/night ambient driven by <see cref="Calendar.DayProgress"/>: a daylight factor (0 at midnight,
+/// 1 at noon) and an ambient color lerped from night to day. <see cref="SampleAt"/> is the sampleable
+/// light interface read by both the renderer (scene darkening) and the simulation (plant light);
+/// it returns the global daylight today and will return locally-shadowed light once point lights and
+/// occlusion land. Pure read-side, GPU-free and deterministic.
+/// </summary>
+public sealed class DayNight
+{
+    private readonly Calendar _calendar;
+    private readonly DayNightSettings _settings;
+
+    /// <summary>Creates the cycle reading <paramref name="calendar"/> with the given <paramref name="settings"/>.</summary>
+    public DayNight(Calendar calendar, DayNightSettings settings)
+    {
+        _calendar = calendar ?? throw new ArgumentNullException(nameof(calendar));
+        _settings = settings;
+    }
+
+    /// <summary>Daylight factor in <c>[0, 1]</c> — 0 at midnight, 1 at noon, 0 again at midnight.</summary>
+    public float Daylight
+    {
+        get
+        {
+            var value = -MathF.Cos(MathF.Tau * _calendar.DayProgress);
+            return value > 0f ? value : 0f;
+        }
+    }
+
+    /// <summary>Global light intensity in <c>[0, 1]</c>; same as <see cref="Daylight"/> today.</summary>
+    public float Intensity => Daylight;
+
+    /// <summary>Light intensity at a world point in <c>[0, 1]</c>. Global today; local (with shadows) later.</summary>
+    public float SampleAt(Vector2 world) => Daylight;
+
+    /// <summary>
+    /// Offset, in grid cells, of the shadow an occluder casts under the current sun: opposite the
+    /// sun's east–west position and longest near sunrise/sunset (low sun), shrinking to zero at noon
+    /// and at night. Feeds the lightmap's directional shadow pass; <paramref name="maxLength"/> caps
+    /// the dawn/dusk shadow length. Tilted slightly "south" (down) so shadows fall in front of objects.
+    /// </summary>
+    public Vector2 SunShadow(float maxLength)
+    {
+        var day = (_calendar.DayProgress - 0.25f) / 0.5f; // daytime fraction over [06:00, 18:00]
+        if (day <= 0f || day >= 1f)
+        {
+            return Vector2.Zero; // night — no sun; the ambient floor handles darkness
+        }
+
+        var altitude = MathF.Sin(day * MathF.PI); // 0 at dawn/dusk, 1 at noon
+        var direction = new Vector2(2f * day - 1f, 0.4f); // sun east→west ⇒ shadow west→east, tilted south
+        direction.Normalize();
+        return direction * (maxLength * (1f - altitude));
+    }
+
+    /// <summary>Ambient tint for the scene: night color at night, day color at noon, eased between.</summary>
+    public Color Ambient
+    {
+        get
+        {
+            var t = Smoothstep(Daylight);
+            return Color.Lerp(_settings.NightColor, _settings.DayColor, t);
+        }
+    }
+
+    private static float Smoothstep(float x) => x * x * (3f - 2f * x);
+}

src/MrGameEng.Graphics/Lighting/DayNightSystem.cs

@@ -0,0 +1,49 @@
+using Friflo.Engine.ECS.Systems;
+using MrGameEng.Core;
+using MrGameEng.Graphics;
+
+namespace MrGameEng.Lighting;
+
+/// <summary>
+/// Update-phase system that pushes the current <see cref="DayNight.Ambient"/> into the renderer's
+/// <see cref="Renderer2D.AmbientLight"/> each frame, so the world darkens toward night and brightens
+/// toward noon. Runs in the update phase, before the draw phase consumes the value.
+/// </summary>
+public sealed class DayNightSystem : BaseSystem
+{
+    private readonly DayNight _dayNight;
+    private readonly Renderer2D _renderer;
+
+    internal DayNightSystem(DayNight dayNight, Renderer2D renderer)
+    {
+        _dayNight = dayNight;
+        _renderer = renderer;
+    }
+
+    /// <inheritdoc />
+    protected override void OnUpdateGroup() => _renderer.AmbientLight = _dayNight.Ambient;
+}
+
+/// <summary>Wires the day/night ambient cycle into a <see cref="Scene"/>.</summary>
+public static class SceneLightingExtensions
+{
+    /// <summary>
+    /// Creates a <see cref="DayNight"/> bound to the scene's <see cref="Calendar"/> service, registers
+    /// it, and drives <paramref name="renderer"/>'s ambient light from it. Call from <c>OnLoad</c>
+    /// after <see cref="CalendarEngineExtensions.UseCalendar"/> and <c>UseRenderer2D</c>.
+    /// </summary>
+    public static DayNight UseDayNight(
+        this Scene scene,
+        Renderer2D renderer,
+        DayNightSettings? settings = null
+    )
+    {
+        var dayNight = new DayNight(
+            scene.Context.Services.Get<Calendar>(),
+            settings ?? DayNightSettings.Default
+        );
+        scene.Context.Services.Add(dayNight);
+        scene.UpdateSystems.Add(new DayNightSystem(dayNight, renderer));
+        return dayNight;
+    }
+}

src/MrGameEng.Graphics/Lighting/Lighting.cs

@@ -0,0 +1,60 @@
+using Microsoft.Xna.Framework;
+using MrGameEng.Core;
+using MrGameEng.Graphics;
+
+namespace MrGameEng.Lighting;
+
+/// <summary>
+/// Scene lighting service: owns the <see cref="Lightmap"/> and exposes a sampleable local light for
+/// the simulation. Built by <see cref="SceneLightmapExtensions.UseLighting"/>, which also registers
+/// the systems that rebuild the lightmap and multiply it over the scene.
+/// </summary>
+public sealed class Lighting
+{
+    /// <summary>The light grid rendered over the world and sampled by the simulation.</summary>
+    public Lightmap Lightmap { get; }
+
+    /// <summary>Creates the service over <paramref name="lightmap"/>.</summary>
+    public Lighting(Lightmap lightmap) => Lightmap = lightmap;
+
+    /// <summary>Local light in <c>[0, 1]</c> at a world point (e.g. for plant growth under canopy).</summary>
+    public float SampleAt(Vector2 world) => Lightmap.SampleAt(world);
+}
+
+/// <summary>Wires the 2D lightmap (day/night × occlusion + point lights) into a <see cref="Scene"/>.</summary>
+public static class SceneLightmapExtensions
+{
+    /// <summary>
+    /// Builds a <see cref="Lighting"/> service for a <paramref name="width"/>×<paramref name="height"/>
+    /// cell world and registers the rebuild and composite systems. Ambient comes from
+    /// <paramref name="dayNight"/>; <paramref name="occluders"/> supplies the current occluder grid
+    /// (row-major, length width×height) each rebuild. Call after <c>UseRenderer2D</c>/<c>UseTilemaps</c>
+    /// and before <c>UseUI</c> so the lightmap composites over the world but under the HUD.
+    /// </summary>
+    public static Lighting UseLighting(
+        this Scene scene,
+        Renderer2D renderer,
+        DayNight dayNight,
+        int width,
+        int height,
+        float cellSize,
+        Vector2 origin,
+        Func<bool[]> occluders
+    )
+    {
+        var device = scene.Context.GetGraphicsDevice();
+        var lightmap = new Lightmap(device, width, height, cellSize, origin);
+        var lighting = new Lighting(lightmap);
+        scene.Context.Services.Add(lighting);
+        RegisterUnloadDispose(scene, lightmap);
+
+        scene.UpdateSystems.Add(
+            new LightmapSystem(scene.Store, lightmap, dayNight, occluders, cellSize, origin)
+        );
+        scene.DrawSystems.Add(new LightmapRenderSystem(device, renderer, lightmap));
+        return lighting;
+    }
+
+    private static void RegisterUnloadDispose(Scene scene, Lightmap lightmap) =>
+        scene.RegisterUnload(lightmap.Dispose);
+}

src/MrGameEng.Graphics/Lighting/Lightmap.cs

@@ -0,0 +1,85 @@
+using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Graphics;
+
+namespace MrGameEng.Lighting;
+
+/// <summary>
+/// A per-cell light grid backed by a greyscale <see cref="Texture2D"/>. <see cref="LightmapBuilder"/>
+/// fills <see cref="Light"/>; <see cref="Upload"/> pushes it to the texture (the renderer multiplies
+/// it over the world for soft, cell-resolution shadows); <see cref="SampleAt"/> reads bilinearly for
+/// the simulation (local light at a plant). The grid maps cell (x,y) to world
+/// <c>Origin + (x+0.5, y+0.5)·CellSize</c>.
+/// </summary>
+public sealed class Lightmap : IDisposable
+{
+    /// <summary>Grid width in cells.</summary>
+    public int Width { get; }
+
+    /// <summary>Grid height in cells.</summary>
+    public int Height { get; }
+
+    /// <summary>World size of one cell.</summary>
+    public float CellSize { get; }
+
+    /// <summary>World position of cell (0,0)'s top-left.</summary>
+    public Vector2 Origin { get; }
+
+    /// <summary>Per-cell light in <c>[0, 1]</c>, row-major. Filled by <see cref="LightmapBuilder"/>.</summary>
+    public float[] Light { get; }
+
+    /// <summary>The greyscale light texture (one texel per cell), updated by <see cref="Upload"/>.</summary>
+    public Texture2D Texture { get; }
+
+    private readonly Color[] _pixels;
+
+    /// <summary>Creates a lightmap grid and its backing texture on <paramref name="device"/>.</summary>
+    public Lightmap(GraphicsDevice device, int width, int height, float cellSize, Vector2 origin)
+    {
+        Width = width;
+        Height = height;
+        CellSize = cellSize;
+        Origin = origin;
+        Light = new float[width * height];
+        _pixels = new Color[width * height];
+        Texture = new Texture2D(device, width, height);
+        Array.Fill(Light, 1f);
+        Upload();
+    }
+
+    /// <summary>Writes the current <see cref="Light"/> grid into the texture as greyscale.</summary>
+    public void Upload()
+    {
+        for (var i = 0; i < Light.Length; i++)
+        {
+            var b = (byte)(Math.Clamp(Light[i], 0f, 1f) * 255f);
+            _pixels[i] = new Color(b, b, b, (byte)255);
+        }
+
+        Texture.SetData(_pixels);
+    }
+
+    /// <summary>Bilinearly samples the light at a world point; clamps at the edges.</summary>
+    public float SampleAt(Vector2 world)
+    {
+        var fx = (world.X - Origin.X) / CellSize - 0.5f;
+        var fy = (world.Y - Origin.Y) / CellSize - 0.5f;
+        fx = Math.Clamp(fx, 0f, Width - 1f);
+        fy = Math.Clamp(fy, 0f, Height - 1f);
+
+        var x0 = (int)fx;
+        var y0 = (int)fy;
+        var x1 = Math.Min(x0 + 1, Width - 1);
+        var y1 = Math.Min(y0 + 1, Height - 1);
+        var tx = fx - x0;
+        var ty = fy - y0;
+
+        var top = Lerp(Light[y0 * Width + x0], Light[y0 * Width + x1], tx);
+        var bottom = Lerp(Light[y1 * Width + x0], Light[y1 * Width + x1], tx);
+        return Lerp(top, bottom, ty);
+    }
+
+    private static float Lerp(float a, float b, float t) => a + (b - a) * t;
+
+    /// <inheritdoc />
+    public void Dispose() => Texture.Dispose();
+}

src/MrGameEng.Graphics/Lighting/LightmapBuilder.cs

@@ -0,0 +1,184 @@
+using Microsoft.Xna.Framework;
+
+namespace MrGameEng.Lighting;
+
+/// <summary>One point light projected onto the light grid: a cell position, a radius in cells and an intensity.</summary>
+public readonly record struct LightSample(int X, int Y, float Radius, float Intensity);
+
+/// <summary>
+/// Builds a per-cell light grid (CPU, GPU-free, testable): an ambient base dimmed under occluders,
+/// plus point lights that attenuate with distance and are blocked by occluders between the source
+/// and the cell (grid-traced shadows). Pure data — a <see cref="Lightmap"/> turns the grid into a
+/// texture and the simulation samples it for local light.
+/// </summary>
+public static class LightmapBuilder
+{
+    /// <summary>How much of the ambient light reaches a cell that is itself an occluder (canopy/shade).</summary>
+    public const float OccluderShade = 0.35f;
+
+    /// <summary>
+    /// Fills <paramref name="light"/> (length <paramref name="width"/>×<paramref name="height"/>) with
+    /// ambient light, shading occluder cells, casts each occluder's directional sun shadow along
+    /// <paramref name="sunShadow"/> (cells), then adds each point light with grid-traced occlusion.
+    /// Values end clamped to <c>[0, 1]</c>. A zero <paramref name="sunShadow"/> or
+    /// <paramref name="sunShadowStrength"/> skips the directional pass (e.g. at night/noon).
+    /// </summary>
+    public static void Build(
+        float[] light,
+        int width,
+        int height,
+        float ambient,
+        ReadOnlySpan<bool> occluders,
+        IReadOnlyList<LightSample> lights,
+        Vector2 sunShadow = default,
+        float sunShadowStrength = 0f
+    )
+    {
+        for (var i = 0; i < light.Length; i++)
+        {
+            light[i] = occluders[i] ? ambient * OccluderShade : ambient;
+        }
+
+        CastSunShadows(light, width, height, occluders, sunShadow, sunShadowStrength);
+
+        foreach (var l in lights)
+        {
+            if (l.Radius <= 0f || l.Intensity <= 0f)
+            {
+                continue;
+            }
+
+            var r = (int)MathF.Ceiling(l.Radius);
+            var minX = Math.Max(0, l.X - r);
+            var maxX = Math.Min(width - 1, l.X + r);
+            var minY = Math.Max(0, l.Y - r);
+            var maxY = Math.Min(height - 1, l.Y + r);
+            for (var y = minY; y <= maxY; y++)
+            {
+                for (var x = minX; x <= maxX; x++)
+                {
+                    var dx = x - l.X;
+                    var dy = y - l.Y;
+                    var d = MathF.Sqrt(dx * dx + dy * dy);
+                    if (d > l.Radius)
+                    {
+                        continue;
+                    }
+
+                    if (!Visible(l.X, l.Y, x, y, occluders, width))
+                    {
+                        continue; // в тени за препятствием
+                    }
+
+                    light[y * width + x] += l.Intensity * (1f - d / l.Radius);
+                }
+            }
+        }
+
+        for (var i = 0; i < light.Length; i++)
+        {
+            light[i] = Math.Clamp(light[i], 0f, 1f);
+        }
+    }
+
+    // Направленная тень от солнца: каждый окклюдер (гора/зрелая крона) отбрасывает тень вдоль
+    // вектора sunShadow (в клетках). Затемнение гуще у основания и тает к концу тени; сами клетки-
+    // окклюдеры не трогаем (они уже затенены). Окклюдеры разрежены, так что проход дёшев.
+    private static void CastSunShadows(
+        float[] light,
+        int width,
+        int height,
+        ReadOnlySpan<bool> occluders,
+        Vector2 sunShadow,
+        float strength
+    )
+    {
+        if (strength <= 0f)
+        {
+            return;
+        }
+
+        var steps = (int)MathF.Ceiling(sunShadow.Length());
+        if (steps <= 0)
+        {
+            return;
+        }
+
+        var stepX = sunShadow.X / steps;
+        var stepY = sunShadow.Y / steps;
+        for (var oy = 0; oy < height; oy++)
+        {
+            for (var ox = 0; ox < width; ox++)
+            {
+                if (!occluders[oy * width + ox])
+                {
+                    continue;
+                }
+
+                for (var s = 1; s <= steps; s++)
+                {
+                    var cx = ox + (int)MathF.Round(stepX * s);
+                    var cy = oy + (int)MathF.Round(stepY * s);
+                    if (cx < 0 || cx >= width || cy < 0 || cy >= height)
+                    {
+                        break;
+                    }
+
+                    var index = cy * width + cx;
+                    if (occluders[index])
+                    {
+                        continue; // тень проходит над другими окклюдерами — они и так тёмные
+                    }
+
+                    var falloff = 1f - (float)(s - 1) / steps; // гуще у основания тени
+                    light[index] *= 1f - strength * falloff;
+                }
+            }
+        }
+    }
+
+    // Есть ли прямая видимость между клетками: проводим линию (Брезенхем) и проверяем
+    // промежуточные клетки на окклюдер (концы исключены).
+    private static bool Visible(
+        int x0,
+        int y0,
+        int x1,
+        int y1,
+        ReadOnlySpan<bool> occluders,
+        int width
+    )
+    {
+        var dx = Math.Abs(x1 - x0);
+        var dy = Math.Abs(y1 - y0);
+        var sx = x0 < x1 ? 1 : -1;
+        var sy = y0 < y1 ? 1 : -1;
+        var err = dx - dy;
+        var x = x0;
+        var y = y0;
+        while (true)
+        {
+            if (x == x1 && y == y1)
+            {
+                return true;
+            }
+
+            if ((x != x0 || y != y0) && occluders[y * width + x])
+            {
+                return false;
+            }
+
+            var e2 = 2 * err;
+            if (e2 > -dy)
+            {
+                err -= dy;
+                x += sx;
+            }
+
+            if (e2 < dx)
+            {
+                err += dx;
+                y += sy;
+            }
+        }
+    }
+}

src/MrGameEng.Graphics/Lighting/LightmapSystems.cs

@@ -0,0 +1,168 @@
+using Friflo.Engine.ECS;
+using Friflo.Engine.ECS.Systems;
+using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Graphics;
+using MrGameEng.Graphics;
+
+namespace MrGameEng.Lighting;
+
+/// <summary>
+/// Rebuilds the lightmap a few times a second: ambient from the day/night cycle, occluder cells from
+/// the game-supplied grid and point lights from the ECS, then uploads it to the texture. Throttled by
+/// frame skipping — the light changes slowly, so 10 Hz looks smooth and keeps cost low.
+/// </summary>
+public sealed class LightmapSystem : BaseSystem
+{
+    private const int RebuildEvery = 6; // ~10 Гц при 60 fps
+    private const float NightFloor = 0.24f; // ночь тусклая, но не чёрная (лунный свет) — чуть светлее, чем было
+    private const float MaxShadowCells = 7f; // макс. длина тени от солнца (на рассвете/закате)
+    private const float SunShadowStrength = 0.5f; // насколько темнеет клетка у основания тени
+
+    private readonly Lightmap _lightmap;
+    private readonly DayNight _dayNight;
+    private readonly Func<bool[]> _occluders;
+    private readonly float _cellSize;
+    private readonly Vector2 _origin;
+    private readonly ArchetypeQuery<Transform2D, PointLight> _query;
+    private readonly List<LightSample> _lights = [];
+    private int _frame;
+
+    internal LightmapSystem(
+        EntityStore store,
+        Lightmap lightmap,
+        DayNight dayNight,
+        Func<bool[]> occluders,
+        float cellSize,
+        Vector2 origin
+    )
+    {
+        _lightmap = lightmap;
+        _dayNight = dayNight;
+        _occluders = occluders;
+        _cellSize = cellSize;
+        _origin = origin;
+        _query = store.Query<Transform2D, PointLight>();
+    }
+
+    /// <inheritdoc />
+    protected override void OnUpdateGroup()
+    {
+        if (++_frame < RebuildEvery)
+        {
+            return;
+        }
+
+        _frame = 0;
+
+        _lights.Clear();
+        foreach (var (transforms, lights, _) in _query.Chunks)
+        {
+            var t = transforms.Span;
+            var l = lights.Span;
+            for (var i = 0; i < t.Length; i++)
+            {
+                if (l[i].Radius <= 0f || l[i].Intensity <= 0f)
+                {
+                    continue;
+                }
+
+                var cx = (int)((t[i].Position.X - _origin.X) / _cellSize);
+                var cy = (int)((t[i].Position.Y - _origin.Y) / _cellSize);
+                _lights.Add(new LightSample(cx, cy, l[i].Radius / _cellSize, l[i].Intensity));
+            }
+        }
+
+        var ambient = NightFloor + (1f - NightFloor) * _dayNight.Intensity;
+        LightmapBuilder.Build(
+            _lightmap.Light,
+            _lightmap.Width,
+            _lightmap.Height,
+            ambient,
+            _occluders(),
+            _lights,
+            _dayNight.SunShadow(MaxShadowCells),
+            SunShadowStrength
+        );
+        _lightmap.Upload();
+    }
+}
+
+/// <summary>
+/// Draws the lightmap over the world as a single texture quad with multiply blending and linear
+/// filtering — the world darkens by the grid and shadows read soft. Registered after the sprite flush
+/// (so it lands on the drawn scene) and before the screen-space UI (so the HUD stays at full brightness).
+/// </summary>
+public sealed class LightmapRenderSystem : BaseSystem
+{
+    private static readonly BlendState Multiply = new()
+    {
+        ColorSourceBlend = Blend.DestinationColor,
+        ColorDestinationBlend = Blend.Zero,
+        AlphaSourceBlend = Blend.DestinationAlpha,
+        AlphaDestinationBlend = Blend.Zero,
+    };
+
+    private readonly GraphicsDevice _device;
+    private readonly Renderer2D _renderer;
+    private readonly Lightmap _lightmap;
+    private readonly BasicEffect _effect;
+    private readonly VertexPositionTexture[] _quad;
+
+    internal LightmapRenderSystem(GraphicsDevice device, Renderer2D renderer, Lightmap lightmap)
+    {
+        _device = device;
+        _renderer = renderer;
+        _lightmap = lightmap;
+        _effect = new BasicEffect(device)
+        {
+            TextureEnabled = true,
+            VertexColorEnabled = false,
+            World = Matrix.Identity,
+        };
+
+        var x0 = lightmap.Origin.X;
+        var y0 = lightmap.Origin.Y;
+        var x1 = x0 + lightmap.Width * lightmap.CellSize;
+        var y1 = y0 + lightmap.Height * lightmap.CellSize;
+        _quad =
+        [
+            new VertexPositionTexture(new Vector3(x0, y0, 0f), new Vector2(0f, 0f)),
+            new VertexPositionTexture(new Vector3(x1, y0, 0f), new Vector2(1f, 0f)),
+            new VertexPositionTexture(new Vector3(x0, y1, 0f), new Vector2(0f, 1f)),
+            new VertexPositionTexture(new Vector3(x1, y0, 0f), new Vector2(1f, 0f)),
+            new VertexPositionTexture(new Vector3(x1, y1, 0f), new Vector2(1f, 1f)),
+            new VertexPositionTexture(new Vector3(x0, y1, 0f), new Vector2(0f, 1f)),
+        ];
+    }
+
+    /// <inheritdoc />
+    protected override void OnUpdateGroup()
+    {
+        var camera = _renderer.Camera;
+        _effect.View = camera.View;
+        _effect.Projection = camera.Projection;
+        _effect.Texture = _lightmap.Texture;
+
+        var previousViewport = _device.Viewport;
+        var mapping = camera.Mapping;
+        _device.Viewport = new Viewport(
+            (int)MathF.Round(mapping.Offset.X),
+            (int)MathF.Round(mapping.Offset.Y),
+            (int)MathF.Round(camera.VirtualWidth * mapping.Scale),
+            (int)MathF.Round(camera.VirtualHeight * mapping.Scale)
+        );
+        _device.BlendState = Multiply;
+        _device.SamplerStates[0] = SamplerState.LinearClamp;
+        _device.DepthStencilState = DepthStencilState.None;
+        _device.RasterizerState = RasterizerState.CullNone;
+
+        foreach (var pass in _effect.CurrentTechnique.Passes)
+        {
+            pass.Apply();
+            _device.DrawUserPrimitives(PrimitiveType.TriangleList, _quad, 0, 2);
+        }
+
+        _device.Viewport = previousViewport;
+        _device.BlendState = BlendState.AlphaBlend;
+    }
+}

src/MrGameEng.Graphics/Lighting/PointLight.cs

@@ -0,0 +1,21 @@
+using Friflo.Engine.ECS;
+using Microsoft.Xna.Framework;
+
+namespace MrGameEng.Lighting;
+
+/// <summary>
+/// A point light: an entity with this component plus a <see cref="MrGameEng.Graphics.Transform2D"/>
+/// adds light around its world position, attenuating to zero at <see cref="Radius"/> and casting
+/// grid-traced shadows behind occluders. Picked up by the lighting system into the lightmap.
+/// </summary>
+public struct PointLight : IComponent
+{
+    /// <summary>Reach of the light in world units (light fades to zero at this distance).</summary>
+    public float Radius;
+
+    /// <summary>Light tint (reserved for colored lights; intensity currently drives brightness).</summary>
+    public Color Color;
+
+    /// <summary>Peak brightness added at the light's centre (0..1+).</summary>
+    public float Intensity;
+}

src/MrGameEng.Graphics/MrGameEng.Graphics.csproj

@@ -3,6 +3,10 @@
     <TargetFramework>net8.0</TargetFramework>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="MonoGame.Framework.DesktopGL" />
+  </ItemGroup>
+
   <ItemGroup>
     <InternalsVisibleTo Include="MrGameEng.Graphics.Tests" />
   </ItemGroup>

src/MrGameEng.Graphics/Renderer2D.cs

@@ -27,6 +27,13 @@ public sealed class Renderer2D : IDisposable
     /// <summary>Camera state of the current frame. Valid between BeginFrame and the next BeginFrame.</summary>
     public CameraState Camera { get; private set; }
 
+    /// <summary>
+    /// Global ambient light multiplied into every <see cref="LayerSpace.World"/> sprite — the engine
+    /// hook a day/night cycle drives. <see cref="Color.White"/> (default) leaves the scene unchanged;
+    /// screen-space layers (HUD overlays) are never tinted.
+    /// </summary>
+    public Color AmbientLight { get; set; } = Color.White;
+
     /// <summary>Draw calls issued by the last <see cref="EndFrame"/>.</summary>
     public int DrawCalls { get; private set; }
 
@@ -338,6 +345,12 @@ public sealed class Renderer2D : IDisposable
         // высоты с origin «в ногах» сортируются по ногам, как принято в top-down.
         var depth = layer.SortMode == LayerSortMode.YSort ? transform.Position.Y : sprite.Depth;
 
+        // Ambient light tints world sprites (day/night); screen-space overlays stay at full brightness.
+        var color =
+            layer.Space == LayerSpace.World && AmbientLight != Color.White
+                ? new Color(sprite.Color.ToVector4() * AmbientLight.ToVector4())
+                : sprite.Color;
+
         instance = new SpriteInstance
         {
             Region = region,
@@ -346,7 +359,7 @@ public sealed class Renderer2D : IDisposable
                 new Vector2(region.Width * transform.Scale.X, region.Height * transform.Scale.Y)
                 / 2f,
             Rotation = transform.Rotation,
-            Color = sprite.Color,
+            Color = color,
             Flip = sprite.Flip,
             Layer = sprite.Layer.Value,
         };

src/MrGameEng.Graphics/SceneGraphicsExtensions.cs

@@ -22,7 +22,7 @@ public static class SceneGraphicsExtensions
         var renderer = services.GetOrDefault<Renderer2D>();
         if (renderer is null)
         {
-            renderer = new Renderer2D(scene.Context.GraphicsDevice, options);
+            renderer = new Renderer2D(scene.Context.GetGraphicsDevice(), options);
             services.Add(renderer);
         }
         else if (options is not null)

src/MrGameEng.Graphics/Texture2DRegion.cs

@@ -43,10 +43,13 @@ public sealed class Texture2DRegion
         // texture может быть null только в headless-тестах.
         if (texture is not null)
         {
-            U0 = bounds.X / (float)texture.Width;
+            // Полутексельный inset: UV идут от центра крайнего текселя к центру крайнего, а не по
-            V0 = bounds.Y / (float)texture.Height;
+            // самым кромкам региона. С point-фильтрацией это гарантирует, что края тайла никогда не
-            U1 = (bounds.X + bounds.Width) / (float)texture.Width;
+            // сэмплят прозрачный «жёлоб» атласа (Padding) — иначе при дробном зуме видны чёрные швы.
-            V1 = (bounds.Y + bounds.Height) / (float)texture.Height;
+            U0 = (bounds.X + 0.5f) / texture.Width;
+            V0 = (bounds.Y + 0.5f) / texture.Height;
+            U1 = (bounds.X + bounds.Width - 0.5f) / texture.Width;
+            V1 = (bounds.Y + bounds.Height - 0.5f) / texture.Height;
         }
     }
 

src/MrGameEng.Host/GameHost.cs

@@ -1,11 +1,16 @@
 using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Graphics;
+using MrGameEng.Core;
 
-namespace MrGameEng.Core;
+namespace MrGameEng.Host;
 
 /// <summary>
-/// The engine's game loop host. Wraps MonoGame's <see cref="Game"/>: owns the
+/// The engine's windowed game-loop host. Wraps MonoGame's <see cref="Game"/>: owns the
-/// <see cref="EngineContext"/>, advances the <see cref="GameClock"/> and drives the
+/// <see cref="EngineContext"/>, advances the <see cref="GameClock"/>, drives the active
-/// active scene's update and draw phases.
+/// scene's update and draw phases and renders scene-transition overlays. The
+/// <see cref="GraphicsDevice"/> is published as a service so graphics modules can reach it
+/// through the context. For a loop without a window or GPU see
+/// <see cref="HeadlessHost"/> in the core.
 /// </summary>
 public class GameHost : Game
 {
@@ -17,6 +22,7 @@ public class GameHost : Game
 
     private readonly GameHostOptions _options;
     private readonly Scene _initialScene;
+    private TransitionRenderer? _transitionRenderer;
 
     /// <summary>Creates a host that starts with <paramref name="initialScene"/>.</summary>
     public GameHost(GameHostOptions options, Scene initialScene)
@@ -48,7 +54,7 @@ public class GameHost : Game
     {
         Window.Title = _options.Title;
         Window.AllowUserResizing = _options.AllowResizing;
-        Context.AttachGraphicsDevice(GraphicsDevice);
+        Context.Services.Add(GraphicsDevice);
         Context.Services.Add(Window);
         Context.Services.Add<Game>(this);
         base.Initialize();
@@ -68,9 +74,25 @@ public class GameHost : Game
     {
         GraphicsDevice.Clear(_options.ClearColor);
         Context.Scenes.Draw(Context.Clock);
+        DrawTransitionOverlay();
         base.Draw(gameTime);
     }
 
+    private void DrawTransitionOverlay()
+    {
+        if (Context.Scenes.ActiveTransition is not OverlayTransition transition)
+        {
+            return;
+        }
+
+        _transitionRenderer ??= new TransitionRenderer(GraphicsDevice);
+        transition.Draw(
+            _transitionRenderer,
+            Context.Scenes.TransitionCoverage,
+            Context.Scenes.TransitionPhase
+        );
+    }
+
     /// <inheritdoc />
     protected override void OnExiting(object sender, ExitingEventArgs args)
     {
@@ -84,7 +106,11 @@ public class GameHost : Game
     {
         if (disposing)
         {
-            Context.DisposeOwnedResources(except: this);
+            _transitionRenderer?.Dispose();
+            _transitionRenderer = null;
+            // GraphicsDevice зарегистрирован как сервис, но им владеет MonoGame:
+            // base.Dispose сам его освобождает, реестру трогать нельзя.
+            Context.DisposeOwnedResources(this, GraphicsDevice);
         }
 
         base.Dispose(disposing);

src/MrGameEng.Host/GameHostOptions.cs

@@ -1,6 +1,6 @@
 using Microsoft.Xna.Framework;
 
-namespace MrGameEng.Core;
+namespace MrGameEng.Host;
 
 /// <summary>Window and loop settings for <see cref="GameHost"/>.</summary>
 public sealed class GameHostOptions

src/MrGameEng.Host/MrGameEng.Host.csproj

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="MonoGame.Framework.DesktopGL" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <InternalsVisibleTo Include="MrGameEng.Host.Tests" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\MrGameEng.Core\MrGameEng.Core.csproj" />
+  </ItemGroup>
+</Project>

src/MrGameEng.Host/TransitionRenderer.cs

@@ -1,11 +1,11 @@
 using Microsoft.Xna.Framework;
 using Microsoft.Xna.Framework.Graphics;
 
-namespace MrGameEng.Core;
+namespace MrGameEng.Host;
 
 /// <summary>
-/// Minimal overlay renderer handed to <see cref="Transition.Draw"/>: fills rectangles in
+/// Minimal overlay renderer handed to <see cref="OverlayTransition.Draw"/>: fills rectangles
-/// normalized screen coordinates (0..1 on both axes) over the rendered scene.
+/// in normalized screen coordinates (0..1 on both axes) over the rendered scene.
 /// </summary>
 public sealed class TransitionRenderer : IDisposable
 {
@@ -13,7 +13,7 @@ public sealed class TransitionRenderer : IDisposable
     private readonly BasicEffect _effect;
     private readonly VertexPositionColor[] _vertices = new VertexPositionColor[6];
 
-    /// <summary>Disposes the GPU effect. Called by <see cref="SceneManager"/> on shutdown.</summary>
+    /// <summary>Disposes the GPU effect. Called by <see cref="GameHost"/> on shutdown.</summary>
     public void Dispose() => _effect.Dispose();
 
     internal TransitionRenderer(GraphicsDevice device)

src/MrGameEng.Host/Transitions.cs

@@ -0,0 +1,66 @@
+using Microsoft.Xna.Framework;
+using MrGameEng.Core;
+
+namespace MrGameEng.Host;
+
+/// <summary>
+/// A scene transition that draws a full-screen overlay through a
+/// <see cref="TransitionRenderer"/>. The timing state machine lives in
+/// <see cref="SceneManager"/>; <see cref="GameHost"/> renders the overlay each draw while a
+/// transition is active. Transitions are stateless and reusable.
+/// </summary>
+public abstract class OverlayTransition : Transition
+{
+    /// <summary>Creates a transition with explicit phase durations.</summary>
+    protected OverlayTransition(float outDuration, float inDuration)
+        : base(outDuration, inDuration) { }
+
+    /// <summary>
+    /// Draws the overlay. <paramref name="coverage"/> is 0 (scene fully visible) to
+    /// 1 (scene fully covered); <paramref name="phase"/> tells which side of the switch this is.
+    /// </summary>
+    public abstract void Draw(TransitionRenderer renderer, float coverage, TransitionPhase phase);
+}
+
+/// <summary>Factories for the built-in visual scene transitions.</summary>
+public static class Transitions
+{
+    /// <summary>Fade through a solid color (black by default). Total duration is split between out and in.</summary>
+    public static Transition Fade(float duration = 0.6f, Color? color = null) =>
+        new FadeTransition(duration / 2f, duration / 2f, color ?? Color.Black);
+
+    /// <summary>A curtain wiping across the screen (black by default). Total duration is split between out and in.</summary>
+    public static Transition Wipe(float duration = 0.6f, Color? color = null) =>
+        new WipeTransition(duration / 2f, duration / 2f, color ?? Color.Black);
+
+    private sealed class FadeTransition(float outDuration, float inDuration, Color color)
+        : OverlayTransition(outDuration, inDuration)
+    {
+        public override void Draw(
+            TransitionRenderer renderer,
+            float coverage,
+            TransitionPhase phase
+        ) => renderer.Fill(0f, 0f, 1f, 1f, color, coverage);
+    }
+
+    private sealed class WipeTransition(float outDuration, float inDuration, Color color)
+        : OverlayTransition(outDuration, inDuration)
+    {
+        public override void Draw(
+            TransitionRenderer renderer,
+            float coverage,
+            TransitionPhase phase
+        )
+        {
+            // Out: шторка растёт слева направо; In: уезжает дальше вправо.
+            if (phase == TransitionPhase.Out)
+            {
+                renderer.Fill(0f, 0f, coverage, 1f, color);
+            }
+            else
+            {
+                renderer.Fill(1f - coverage, 0f, coverage, 1f, color);
+            }
+        }
+    }
+}

src/MrGameEng.Net/INetConnection.cs

@@ -0,0 +1,25 @@
+namespace MrGameEng.Net;
+
+/// <summary>
+/// A bidirectional, reliable, ordered binary message channel (a WebSocket under the hood).
+/// Receiving is poll-based to fit the simulation loop: incoming messages queue up on a
+/// background reader and are drained with <see cref="TryReceive"/> from the tick. Sending
+/// never blocks the caller. Implementations are safe to use from one simulation thread.
+/// </summary>
+public interface INetConnection
+{
+    /// <summary>Connection id, unique within its owner (server-assigned; 0 for a client's own connection).</summary>
+    int Id { get; }
+
+    /// <summary>False once the peer disconnected or the connection failed; sends become no-ops.</summary>
+    bool IsOpen { get; }
+
+    /// <summary>Queues one binary message for delivery. No-op when the connection is closed.</summary>
+    void Send(ReadOnlySpan<byte> message);
+
+    /// <summary>Dequeues the next received binary message, if any.</summary>
+    bool TryReceive(out byte[] message);
+
+    /// <summary>Closes the connection.</summary>
+    void Close();
+}

src/MrGameEng.Net/MrGameEng.Net.csproj

@@ -0,0 +1,18 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Friflo.Engine.ECS" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <InternalsVisibleTo Include="MrGameEng.Net.Tests" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\MrGameEng.Core\MrGameEng.Core.csproj" />
+  </ItemGroup>
+</Project>

src/MrGameEng.Net/Replication/NetId.cs

@@ -0,0 +1,14 @@
+using Friflo.Engine.ECS;
+
+namespace MrGameEng.Net;
+
+/// <summary>
+/// Marks an entity as replicated and identifies it across the network. The server assigns
+/// values (see <see cref="ReplicationServer.NextNetId"/>); the client creates a local
+/// entity with the same <see cref="Value"/> when the first snapshot arrives.
+/// </summary>
+public struct NetId : IComponent
+{
+    /// <summary>Network-wide entity id, unique per server world.</summary>
+    public int Value;
+}

src/MrGameEng.Net/Replication/ReplicationClient.cs

@@ -0,0 +1,137 @@
+using Friflo.Engine.ECS;
+using MrGameEng.Core;
+
+namespace MrGameEng.Net;
+
+/// <summary>
+/// Client side of replication: applies snapshot messages from a
+/// <see cref="ReplicationServer"/> to a local <see cref="EntityStore"/>. Unknown net ids
+/// spawn local entities (carrying <see cref="NetId"/>), known ones get their changed
+/// components overwritten, despawns delete. The game decorates replicated entities with
+/// presentation components (sprites etc.) on top — replication never touches types outside
+/// its <see cref="ReplicationSchema"/>.
+/// </summary>
+public sealed class ReplicationClient
+{
+    /// <summary>Number of replicated entities currently alive locally.</summary>
+    public int EntityCount => _entities.Count;
+
+    /// <summary>Raised after an entity is created from a snapshot. Hook presentation setup here.</summary>
+    public event Action<Entity>? EntitySpawned;
+
+    private readonly ReplicationSchema _schema;
+    private readonly EntityStore _store;
+    private readonly Dictionary<int, Entity> _entities = [];
+    private bool _warnedVersion;
+
+    /// <summary>Creates a replication client writing into <paramref name="store"/>.</summary>
+    public ReplicationClient(ReplicationSchema schema, EntityStore store)
+    {
+        _schema = schema;
+        _store = store;
+    }
+
+    /// <summary>Applies every message queued on <paramref name="connection"/>.</summary>
+    public void Pump(INetConnection connection)
+    {
+        while (connection.TryReceive(out var message))
+        {
+            Apply(message);
+        }
+    }
+
+    /// <summary>
+    /// Deletes every replicated entity and forgets all net ids. Call before reconnecting: the
+    /// fresh connection receives the full world again with a clean id space, so stale entities
+    /// from the previous session don't linger as duplicates.
+    /// </summary>
+    public void Clear()
+    {
+        foreach (var entity in _entities.Values)
+        {
+            entity.DeleteEntity();
+        }
+
+        _entities.Clear();
+    }
+
+    /// <summary>Applies one snapshot message to the local store.</summary>
+    public void Apply(byte[] message)
+    {
+        using var reader = new BinaryReader(new MemoryStream(message));
+        // Заголовок: тип(1) + версия(1). Короче — точно не наш снапшот.
+        if (message.Length < 2 || reader.ReadByte() != ReplicationMessage.Snapshot)
+        {
+            return; // незнакомый тип сообщения — пропускаем, это не снапшот
+        }
+
+        var version = reader.ReadByte();
+        if (version != ReplicationMessage.ProtocolVersion)
+        {
+            if (!_warnedVersion)
+            {
+                _warnedVersion = true;
+                Log.Warning(
+                    $"Replication protocol mismatch: server v{version}, client "
+                        + $"v{ReplicationMessage.ProtocolVersion} — snapshots dropped. Schemas out of sync."
+                );
+            }
+
+            return;
+        }
+
+        var slots = _schema.Slots;
+        try
+        {
+            var count = reader.ReadInt32();
+            for (var record = 0; record < count; record++)
+            {
+                var netId = reader.ReadInt32();
+                var op = reader.ReadByte();
+                if (op == ReplicationMessage.OpDespawn)
+                {
+                    if (_entities.Remove(netId, out var dead))
+                    {
+                        dead.DeleteEntity();
+                    }
+
+                    continue;
+                }
+
+                var mask = reader.ReadUInt32();
+                var spawned = false;
+                if (!_entities.TryGetValue(netId, out var entity))
+                {
+                    entity = _store.CreateEntity(new NetId { Value = netId });
+                    _entities[netId] = entity;
+                    spawned = true;
+                }
+
+                foreach (var slot in slots)
+                {
+                    if ((mask & (1u << slot.Bit)) == 0)
+                    {
+                        continue;
+                    }
+
+                    var data = reader.ReadBytes(slot.Size);
+                    if (data.Length < slot.Size)
+                    {
+                        return; // снапшот оборван на полпути — дальше читать нечего
+                    }
+
+                    slot.Apply(entity, data, 0);
+                }
+
+                if (spawned)
+                {
+                    EntitySpawned?.Invoke(entity);
+                }
+            }
+        }
+        catch (EndOfStreamException)
+        {
+            // Структурно битый/усечённый снапшот — игнорируем остаток, соединение не роняем.
+        }
+    }
+}

src/MrGameEng.Net/Replication/ReplicationSchema.cs

@@ -0,0 +1,64 @@
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Friflo.Engine.ECS;
+
+namespace MrGameEng.Net;
+
+/// <summary>
+/// The set of component types a game replicates, registered in the same order on the
+/// server and every client (the order defines the wire ids). Components must be
+/// unmanaged structs — they are blitted to the wire as raw bytes, so server and client
+/// must run on the same engine version. Up to 32 types.
+/// </summary>
+public sealed class ReplicationSchema
+{
+    internal sealed class ComponentSlot
+    {
+        public required int Bit;
+        public required int Size;
+        public required Func<Entity, byte[], bool> TryWrite;
+        public required Action<Entity, byte[], int> Apply;
+    }
+
+    internal readonly List<ComponentSlot> Slots = [];
+
+    /// <summary>
+    /// Registers component type <typeparamref name="T"/> for replication. Returns this
+    /// schema for fluent chaining.
+    /// </summary>
+    public ReplicationSchema Register<T>()
+        where T : unmanaged, IComponent
+    {
+        if (Slots.Count == 32)
+        {
+            throw new InvalidOperationException(
+                "ReplicationSchema supports at most 32 component types."
+            );
+        }
+
+        var size = Unsafe.SizeOf<T>();
+        Slots.Add(
+            new ComponentSlot
+            {
+                Bit = Slots.Count,
+                Size = size,
+                TryWrite = (entity, buffer) =>
+                {
+                    if (!entity.HasComponent<T>())
+                    {
+                        return false;
+                    }
+
+                    MemoryMarshal.Write(buffer, in entity.GetComponent<T>());
+                    return true;
+                },
+                Apply = (entity, data, offset) =>
+                {
+                    var value = MemoryMarshal.Read<T>(data.AsSpan(offset, size));
+                    entity.AddComponent(value);
+                },
+            }
+        );
+        return this;
+    }
+}

src/MrGameEng.Net/Replication/ReplicationServer.cs

@@ -0,0 +1,183 @@
+using Friflo.Engine.ECS;
+
+namespace MrGameEng.Net;
+
+/// <summary>
+/// Server-authoritative component replication. Each call to <see cref="Send"/> snapshots
+/// every entity carrying <see cref="NetId"/> and sends each connection only what changed
+/// since that connection's previous snapshot (per-component deltas; a new connection gets
+/// the full state the same way). Deltas need no acknowledgements because the transport is
+/// reliable and ordered. Call at the desired send rate (e.g. every Nth simulation tick),
+/// from the simulation thread.
+/// </summary>
+public sealed class ReplicationServer
+{
+    private sealed class ConnectionState
+    {
+        // По netId: последний отправленный блоб каждого зарегистрированного компонента.
+        public readonly Dictionary<int, byte[]?[]> LastSent = [];
+    }
+
+    private readonly ReplicationSchema _schema;
+    private readonly ArchetypeQuery<NetId> _query;
+    private readonly Dictionary<INetConnection, ConnectionState> _states = [];
+
+    // Снапшот текущего тика, переиспользуется между соединениями.
+    private readonly List<(int NetId, byte[]?[] Components)> _current = [];
+    private readonly HashSet<int> _currentIds = [];
+    private int _nextNetId;
+
+    /// <summary>Creates a replication server over <paramref name="store"/>.</summary>
+    public ReplicationServer(ReplicationSchema schema, EntityStore store)
+    {
+        _schema = schema;
+        _query = store.Query<NetId>();
+    }
+
+    /// <summary>Allocates the next free network id for a newly spawned replicated entity.</summary>
+    public int NextNetId() => ++_nextNetId;
+
+    /// <summary>
+    /// Snapshots the world once and sends per-connection deltas. Closed connections are
+    /// forgotten; brand-new ones receive the full state.
+    /// </summary>
+    public void Send(IReadOnlyList<INetConnection> connections)
+    {
+        CaptureCurrentState();
+
+        foreach (var connection in connections)
+        {
+            if (!connection.IsOpen)
+            {
+                continue;
+            }
+
+            if (!_states.TryGetValue(connection, out var state))
+            {
+                state = new ConnectionState();
+                _states[connection] = state;
+            }
+
+            var message = BuildDelta(state);
+            if (message is not null)
+            {
+                connection.Send(message);
+            }
+        }
+
+        // Забываем состояние умерших соединений, чтобы не копить мусор.
+        foreach (var dead in _states.Keys.Where(c => !c.IsOpen).ToList())
+        {
+            _states.Remove(dead);
+        }
+    }
+
+    private void CaptureCurrentState()
+    {
+        _current.Clear();
+        _currentIds.Clear();
+        var slots = _schema.Slots;
+        _query.ForEachEntity(
+            (ref NetId netId, Entity entity) =>
+            {
+                var components = new byte[]?[slots.Count];
+                foreach (var slot in slots)
+                {
+                    var buffer = new byte[slot.Size];
+                    components[slot.Bit] = slot.TryWrite(entity, buffer) ? buffer : null;
+                }
+
+                _current.Add((netId.Value, components));
+                _currentIds.Add(netId.Value);
+            }
+        );
+    }
+
+    private byte[]? BuildDelta(ConnectionState state)
+    {
+        using var stream = new MemoryStream();
+        using var writer = new BinaryWriter(stream);
+        writer.Write(ReplicationMessage.Snapshot);
+        writer.Write(ReplicationMessage.ProtocolVersion); // версия формата — клиент отвергает чужую
+        var countPosition = stream.Position;
+        writer.Write(0); // количество записей, допишем в конце
+        var records = 0;
+
+        foreach (var (netId, components) in _current)
+        {
+            if (!state.LastSent.TryGetValue(netId, out var lastSent))
+            {
+                lastSent = new byte[]?[components.Length];
+                state.LastSent[netId] = lastSent;
+            }
+
+            uint mask = 0;
+            for (var bit = 0; bit < components.Length; bit++)
+            {
+                var current = components[bit];
+                if (current is null)
+                {
+                    continue;
+                }
+
+                if (lastSent[bit] is null || !current.AsSpan().SequenceEqual(lastSent[bit]))
+                {
+                    mask |= 1u << bit;
+                    lastSent[bit] = current;
+                }
+            }
+
+            if (mask == 0)
+            {
+                continue;
+            }
+
+            writer.Write(netId);
+            writer.Write(ReplicationMessage.OpUpsert);
+            writer.Write(mask);
+            for (var bit = 0; bit < components.Length; bit++)
+            {
+                if ((mask & (1u << bit)) != 0)
+                {
+                    writer.Write(components[bit]!);
+                }
+            }
+
+            records++;
+        }
+
+        // Сущности, которые соединение знает, а в мире их больше нет.
+        foreach (var known in state.LastSent.Keys.Where(id => !_currentIds.Contains(id)).ToList())
+        {
+            state.LastSent.Remove(known);
+            writer.Write(known);
+            writer.Write(ReplicationMessage.OpDespawn);
+            records++;
+        }
+
+        if (records == 0)
+        {
+            return null;
+        }
+
+        stream.Position = countPosition;
+        writer.Write(records);
+        return stream.ToArray();
+    }
+}
+
+/// <summary>Wire constants shared by <see cref="ReplicationServer"/> and <see cref="ReplicationClient"/>.</summary>
+internal static class ReplicationMessage
+{
+    internal const byte Snapshot = 1;
+
+    /// <summary>
+    /// Wire-format version. Bump whenever the snapshot layout or the meaning of the schema's
+    /// component blits changes; a client receiving a mismatched version drops the message
+    /// instead of decoding garbage (guards against a desync between server and client schemas).
+    /// </summary>
+    internal const byte ProtocolVersion = 1;
+
+    internal const byte OpUpsert = 0;
+    internal const byte OpDespawn = 1;
+}

src/MrGameEng.Net/WebSocketClient.cs

@@ -0,0 +1,149 @@
+using System.Collections.Concurrent;
+using System.Net.WebSockets;
+
+namespace MrGameEng.Net;
+
+/// <summary>
+/// Client side of <see cref="INetConnection"/>: a thin wrapper over the BCL
+/// <see cref="ClientWebSocket"/>, which works on desktop and inside Blazor WebAssembly
+/// (where it maps to the browser's WebSocket). Receiving runs on a background task into a
+/// queue; sends are chained fire-and-forget so the caller — and the browser's single
+/// thread — never blocks.
+/// </summary>
+public sealed class WebSocketClient : INetConnection, IDisposable
+{
+    /// <inheritdoc />
+    public int Id => 0;
+
+    /// <inheritdoc />
+    public bool IsOpen => !_closed && _socket.State == WebSocketState.Open;
+
+    private readonly ClientWebSocket _socket;
+    private readonly ConcurrentQueue<byte[]> _inbox = new();
+    private readonly CancellationTokenSource _shutdown = new();
+    private Task _sendTail = Task.CompletedTask;
+    private volatile bool _closed;
+
+    private WebSocketClient(ClientWebSocket socket) => _socket = socket;
+
+    /// <summary>
+    /// Connects to <paramref name="uri"/> (ws:// or wss://) and starts the receive loop.
+    /// </summary>
+    public static async Task<WebSocketClient> ConnectAsync(
+        Uri uri,
+        CancellationToken cancellationToken = default
+    )
+    {
+        var socket = new ClientWebSocket();
+        await socket.ConnectAsync(uri, cancellationToken).ConfigureAwait(false);
+        var client = new WebSocketClient(socket);
+        _ = Task.Run(client.ReceiveLoop);
+        return client;
+    }
+
+    /// <inheritdoc />
+    public void Send(ReadOnlySpan<byte> message)
+    {
+        if (!IsOpen)
+        {
+            return;
+        }
+
+        var copy = message.ToArray();
+        // Отправки сцеплены в хвост: ClientWebSocket не терпит параллельных SendAsync,
+        // а блокировать поток нельзя (в wasm это смерть).
+        lock (_shutdown)
+        {
+            _sendTail = _sendTail.ContinueWith(
+                _ => SendCore(copy),
+                CancellationToken.None,
+                TaskContinuationOptions.None,
+                TaskScheduler.Default
+            );
+        }
+    }
+
+    private async Task SendCore(byte[] message)
+    {
+        try
+        {
+            await _socket
+                .SendAsync(
+                    message,
+                    WebSocketMessageType.Binary,
+                    endOfMessage: true,
+                    _shutdown.Token
+                )
+                .ConfigureAwait(false);
+        }
+        catch (Exception)
+        {
+            Close();
+        }
+    }
+
+    /// <inheritdoc />
+    public bool TryReceive(out byte[] message) => _inbox.TryDequeue(out message!);
+
+    /// <inheritdoc />
+    public void Close()
+    {
+        if (_closed)
+        {
+            return;
+        }
+
+        _closed = true;
+        _shutdown.Cancel();
+        _socket.Dispose();
+    }
+
+    /// <summary>Closes the connection.</summary>
+    public void Dispose() => Close();
+
+    /// <summary>Largest reassembled message accepted from the server before the connection is dropped.</summary>
+    public const int MaxMessageBytes = 16 * 1024 * 1024;
+
+    private async Task ReceiveLoop()
+    {
+        var buffer = new byte[64 * 1024];
+        var message = new MemoryStream();
+        try
+        {
+            while (!_closed)
+            {
+                var result = await _socket
+                    .ReceiveAsync(buffer, _shutdown.Token)
+                    .ConfigureAwait(false);
+                if (result.MessageType == WebSocketMessageType.Close)
+                {
+                    break;
+                }
+
+                if (message.Length + result.Count > MaxMessageBytes)
+                {
+                    break; // сервер шлёт ненормально большое сообщение — рвём соединение
+                }
+
+                message.Write(buffer, 0, result.Count);
+                if (result.EndOfMessage)
+                {
+                    if (result.MessageType == WebSocketMessageType.Binary)
+                    {
+                        _inbox.Enqueue(message.ToArray());
+                    }
+
+                    message.SetLength(0);
+                }
+            }
+        }
+        catch (Exception)
+        {
+            // обрыв или закрытие — штатное завершение цикла
+        }
+        finally
+        {
+            Close();
+        }
+    }
+}

src/MrGameEng.Net/WebSocketProtocol.cs

@@ -0,0 +1,248 @@
+using System.Buffers.Binary;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace MrGameEng.Net;
+
+/// <summary>WebSocket frame opcodes used by the server.</summary>
+internal enum WebSocketOpcode : byte
+{
+    Continuation = 0x0,
+    Text = 0x1,
+    Binary = 0x2,
+    Close = 0x8,
+    Ping = 0x9,
+    Pong = 0xA,
+}
+
+/// <summary>
+/// Minimal RFC 6455 building blocks for the server side: the upgrade handshake and frame
+/// encode/decode over a <see cref="Stream"/>. Kept free of sockets so the protocol logic is
+/// unit-testable; <see cref="WebSocketServer"/> wires it to TCP.
+/// </summary>
+internal static class WebSocketProtocol
+{
+    private const string HandshakeGuid = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
+
+    /// <summary>Computes the Sec-WebSocket-Accept value for a client's Sec-WebSocket-Key.</summary>
+    internal static string AcceptKey(string secWebSocketKey)
+    {
+        var bytes = Encoding.ASCII.GetBytes(secWebSocketKey + HandshakeGuid);
+        return Convert.ToBase64String(SHA1.HashData(bytes));
+    }
+
+    /// <summary>
+    /// Reads the HTTP upgrade request from <paramref name="stream"/> (up to the blank line)
+    /// and extracts the Sec-WebSocket-Key header. Returns false on a malformed request.
+    /// </summary>
+    internal static bool TryReadHandshakeKey(Stream stream, out string key)
+    {
+        key = "";
+        var buffer = new byte[8 * 1024];
+        var length = 0;
+        // Читаем до конца заголовков (\r\n\r\n); запрос маленький, побайтовое чтение не больно.
+        while (length < buffer.Length)
+        {
+            var read = stream.Read(buffer, length, 1);
+            if (read == 0)
+            {
+                return false;
+            }
+
+            length++;
+            if (
+                length >= 4
+                && buffer[length - 4] == (byte)'\r'
+                && buffer[length - 3] == (byte)'\n'
+                && buffer[length - 2] == (byte)'\r'
+                && buffer[length - 1] == (byte)'\n'
+            )
+            {
+                break;
+            }
+        }
+
+        var request = Encoding.ASCII.GetString(buffer, 0, length);
+        foreach (var line in request.Split("\r\n"))
+        {
+            var separator = line.IndexOf(':');
+            if (separator < 0)
+            {
+                continue;
+            }
+
+            if (
+                line[..separator]
+                    .Trim()
+                    .Equals("Sec-WebSocket-Key", StringComparison.OrdinalIgnoreCase)
+            )
+            {
+                key = line[(separator + 1)..].Trim();
+                return key.Length > 0;
+            }
+        }
+
+        return false;
+    }
+
+    /// <summary>Writes the 101 Switching Protocols response completing the handshake.</summary>
+    internal static void WriteHandshakeResponse(Stream stream, string secWebSocketKey)
+    {
+        var response =
+            "HTTP/1.1 101 Switching Protocols\r\n"
+            + "Upgrade: websocket\r\n"
+            + "Connection: Upgrade\r\n"
+            + $"Sec-WebSocket-Accept: {AcceptKey(secWebSocketKey)}\r\n"
+            + "\r\n";
+        var bytes = Encoding.ASCII.GetBytes(response);
+        stream.Write(bytes, 0, bytes.Length);
+    }
+
+    /// <summary>
+    /// Encodes one complete (FIN) frame. Server frames are unmasked per RFC 6455;
+    /// <paramref name="maskKey"/> is for tests that emulate a client.
+    /// </summary>
+    internal static byte[] EncodeFrame(
+        ReadOnlySpan<byte> payload,
+        WebSocketOpcode opcode,
+        byte[]? maskKey = null
+    )
+    {
+        var masked = maskKey is not null;
+        var headerLength =
+            2
+            + payload.Length switch
+            {
+                <= 125 => 0,
+                <= ushort.MaxValue => 2,
+                _ => 8,
+            };
+        var frame = new byte[headerLength + (masked ? 4 : 0) + payload.Length];
+        frame[0] = (byte)(0x80 | (byte)opcode);
+        switch (payload.Length)
+        {
+            case <= 125:
+                frame[1] = (byte)payload.Length;
+                break;
+            case <= ushort.MaxValue:
+                frame[1] = 126;
+                BinaryPrimitives.WriteUInt16BigEndian(frame.AsSpan(2), (ushort)payload.Length);
+                break;
+            default:
+                frame[1] = 127;
+                BinaryPrimitives.WriteUInt64BigEndian(frame.AsSpan(2), (ulong)payload.Length);
+                break;
+        }
+
+        var offset = headerLength;
+        if (masked)
+        {
+            frame[1] |= 0x80;
+            maskKey!.CopyTo(frame, offset);
+            offset += 4;
+            for (var i = 0; i < payload.Length; i++)
+            {
+                frame[offset + i] = (byte)(payload[i] ^ maskKey[i % 4]);
+            }
+        }
+        else
+        {
+            payload.CopyTo(frame.AsSpan(offset));
+        }
+
+        return frame;
+    }
+
+    /// <summary>
+    /// Reads one frame. Returns false on a clean end of stream. Masked payloads are unmasked.
+    /// </summary>
+    internal static bool TryReadFrame(
+        Stream stream,
+        out WebSocketOpcode opcode,
+        out bool fin,
+        out byte[] payload
+    )
+    {
+        opcode = WebSocketOpcode.Close;
+        fin = true;
+        payload = [];
+
+        var header = new byte[2];
+        if (!TryReadExactly(stream, header))
+        {
+            return false;
+        }
+
+        fin = (header[0] & 0x80) != 0;
+        opcode = (WebSocketOpcode)(header[0] & 0x0F);
+        var masked = (header[1] & 0x80) != 0;
+        long length = header[1] & 0x7F;
+        if (length == 126)
+        {
+            var extended = new byte[2];
+            if (!TryReadExactly(stream, extended))
+            {
+                return false;
+            }
+
+            length = BinaryPrimitives.ReadUInt16BigEndian(extended);
+        }
+        else if (length == 127)
+        {
+            var extended = new byte[8];
+            if (!TryReadExactly(stream, extended))
+            {
+                return false;
+            }
+
+            length = (long)BinaryPrimitives.ReadUInt64BigEndian(extended);
+        }
+
+        if (length > MaxPayloadBytes)
+        {
+            return false; // защита от злонамеренной длины — соединение закроется
+        }
+
+        var maskKey = new byte[4];
+        if (masked && !TryReadExactly(stream, maskKey))
+        {
+            return false;
+        }
+
+        payload = new byte[length];
+        if (!TryReadExactly(stream, payload))
+        {
+            return false;
+        }
+
+        if (masked)
+        {
+            for (var i = 0; i < payload.Length; i++)
+            {
+                payload[i] ^= maskKey[i % 4];
+            }
+        }
+
+        return true;
+    }
+
+    /// <summary>Upper bound for a single frame payload accepted by the server.</summary>
+    internal const int MaxPayloadBytes = 16 * 1024 * 1024;
+
+    private static bool TryReadExactly(Stream stream, byte[] buffer)
+    {
+        var offset = 0;
+        while (offset < buffer.Length)
+        {
+            var read = stream.Read(buffer, offset, buffer.Length - offset);
+            if (read == 0)
+            {
+                return false;
+            }
+
+            offset += read;
+        }
+
+        return true;
+    }
+}

src/MrGameEng.Net/WebSocketServer.cs

@@ -0,0 +1,372 @@
+using System.Collections.Concurrent;
+using System.Net;
+using System.Net.Sockets;
+using MrGameEng.Core;
+
+namespace MrGameEng.Net;
+
+/// <summary>
+/// A dependency-free WebSocket server (RFC 6455 over <see cref="TcpListener"/>) for
+/// dedicated servers. Accepting and reading happen on background tasks; the simulation
+/// drains new connections with <see cref="TryAcceptConnection"/> and reads messages by
+/// polling each connection — nothing here touches the ECS world from another thread.
+/// Binary messages only; incoming pings are answered automatically and the server itself
+/// heartbeats each connection, closing any that goes silent past <see cref="IdleTimeout"/>
+/// (detects half-open TCP — a peer that vanished without a close frame). A reassembled
+/// message is capped at <see cref="MaxMessageBytes"/> so a peer can't exhaust memory.
+/// </summary>
+public sealed class WebSocketServer : IDisposable
+{
+    /// <summary>Largest reassembled (possibly fragmented) message accepted from a peer.</summary>
+    public const int MaxMessageBytes = WebSocketProtocol.MaxPayloadBytes;
+
+    /// <summary>The port the server listens on.</summary>
+    public int Port { get; }
+
+    /// <summary>How often the server pings each connection to keep it alive and probe liveness.</summary>
+    public TimeSpan HeartbeatInterval { get; }
+
+    /// <summary>A connection with no traffic for longer than this is considered dead and closed.</summary>
+    public TimeSpan IdleTimeout { get; }
+
+    /// <summary>Snapshot of currently open connections.</summary>
+    public IReadOnlyList<INetConnection> Connections
+    {
+        get
+        {
+            lock (_connections)
+            {
+                return _connections.Where(c => c.IsOpen).Cast<INetConnection>().ToArray();
+            }
+        }
+    }
+
+    private readonly TcpListener _listener;
+    private readonly List<ServerConnection> _connections = [];
+    private readonly ConcurrentQueue<ServerConnection> _accepted = new();
+    private readonly CancellationTokenSource _shutdown = new();
+    private int _nextConnectionId;
+    private bool _started;
+
+    /// <summary>
+    /// Creates a server for <paramref name="port"/> on all interfaces. Call <see cref="Start"/>
+    /// to listen. <paramref name="heartbeatInterval"/> (default 10 s) sets how often each
+    /// connection is pinged; <paramref name="idleTimeout"/> (default 30 s) how long a silent
+    /// connection lives before it's dropped as dead. The timeout must exceed the interval so a
+    /// healthy peer's pong lands before it's judged idle.
+    /// </summary>
+    public WebSocketServer(
+        int port,
+        TimeSpan? heartbeatInterval = null,
+        TimeSpan? idleTimeout = null
+    )
+    {
+        Port = port;
+        HeartbeatInterval = heartbeatInterval ?? TimeSpan.FromSeconds(10);
+        IdleTimeout = idleTimeout ?? TimeSpan.FromSeconds(30);
+        _listener = new TcpListener(IPAddress.Any, port);
+    }
+
+    /// <summary>Starts listening and accepting connections in the background.</summary>
+    public void Start()
+    {
+        if (_started)
+        {
+            return;
+        }
+
+        _started = true;
+        _listener.Start();
+        Task.Run(AcceptLoop);
+        Task.Run(HeartbeatLoop);
+        Log.Info($"WebSocketServer listening on port {Port}");
+    }
+
+    /// <summary>Dequeues a connection that completed its handshake since the last call.</summary>
+    public bool TryAcceptConnection(out INetConnection connection)
+    {
+        if (_accepted.TryDequeue(out var accepted))
+        {
+            connection = accepted;
+            return true;
+        }
+
+        connection = null!;
+        return false;
+    }
+
+    /// <summary>Stops listening and closes every connection.</summary>
+    public void Dispose()
+    {
+        _shutdown.Cancel();
+        _listener.Stop();
+        lock (_connections)
+        {
+            foreach (var connection in _connections)
+            {
+                connection.Close();
+            }
+
+            _connections.Clear();
+        }
+    }
+
+    private async Task AcceptLoop()
+    {
+        while (!_shutdown.IsCancellationRequested)
+        {
+            TcpClient client;
+            try
+            {
+                client = await _listener.AcceptTcpClientAsync(_shutdown.Token);
+            }
+            catch (Exception) when (_shutdown.IsCancellationRequested)
+            {
+                return;
+            }
+            catch (Exception exception)
+            {
+                Log.Warning($"WebSocketServer accept failed: {exception.Message}");
+                continue;
+            }
+
+            _ = Task.Run(() => Handshake(client));
+        }
+    }
+
+    // Пингует живые соединения и закрывает те, что молчат дольше IdleTimeout (мёртвый peer
+    // не отвечает pong'ом — его активность не обновляется и он отваливается по таймауту).
+    private async Task HeartbeatLoop()
+    {
+        while (!_shutdown.IsCancellationRequested)
+        {
+            try
+            {
+                await Task.Delay(HeartbeatInterval, _shutdown.Token);
+            }
+            catch (OperationCanceledException)
+            {
+                return;
+            }
+
+            ServerConnection[] snapshot;
+            lock (_connections)
+            {
+                snapshot = _connections.ToArray();
+            }
+
+            var now = DateTime.UtcNow;
+            foreach (var connection in snapshot)
+            {
+                if (!connection.IsOpen)
+                {
+                    continue;
+                }
+
+                if (now - connection.LastActivityUtc > IdleTimeout)
+                {
+                    Log.Info($"WebSocketServer: connection #{connection.Id} timed out (idle)");
+                    connection.Close();
+                }
+                else
+                {
+                    connection.SendPing();
+                }
+            }
+        }
+    }
+
+    private void Handshake(TcpClient client)
+    {
+        try
+        {
+            client.NoDelay = true;
+            var stream = client.GetStream();
+            if (!WebSocketProtocol.TryReadHandshakeKey(stream, out var key))
+            {
+                client.Dispose();
+                return;
+            }
+
+            WebSocketProtocol.WriteHandshakeResponse(stream, key);
+            var connection = new ServerConnection(
+                Interlocked.Increment(ref _nextConnectionId),
+                client
+            );
+            lock (_connections)
+            {
+                _connections.RemoveAll(c => !c.IsOpen);
+                _connections.Add(connection);
+            }
+
+            _accepted.Enqueue(connection);
+            connection.StartReceiveLoop();
+            Log.Info($"WebSocketServer: connection #{connection.Id} accepted");
+        }
+        catch (Exception exception)
+        {
+            Log.Warning($"WebSocketServer handshake failed: {exception.Message}");
+            client.Dispose();
+        }
+    }
+
+    private sealed class ServerConnection : INetConnection
+    {
+        public int Id { get; }
+        public bool IsOpen => !_closed;
+
+        /// <summary>UTC of the last frame received from the peer — drives idle-timeout detection.</summary>
+        public DateTime LastActivityUtc =>
+            new(Volatile.Read(ref _lastActivityTicks), DateTimeKind.Utc);
+
+        private readonly TcpClient _client;
+        private readonly NetworkStream _stream;
+        private readonly ConcurrentQueue<byte[]> _inbox = new();
+        private readonly object _sendLock = new();
+        private volatile bool _closed;
+        private long _lastActivityTicks;
+
+        internal ServerConnection(int id, TcpClient client)
+        {
+            Id = id;
+            _client = client;
+            _stream = client.GetStream();
+            _lastActivityTicks = DateTime.UtcNow.Ticks;
+        }
+
+        internal void StartReceiveLoop() => Task.Run(ReceiveLoop);
+
+        /// <summary>Sends a heartbeat ping; a live peer answers with a pong, refreshing activity.</summary>
+        internal void SendPing() => SendControl(WebSocketOpcode.Ping, []);
+
+        public void Send(ReadOnlySpan<byte> message)
+        {
+            if (_closed)
+            {
+                return;
+            }
+
+            var frame = WebSocketProtocol.EncodeFrame(message, WebSocketOpcode.Binary);
+            try
+            {
+                lock (_sendLock)
+                {
+                    _stream.Write(frame, 0, frame.Length);
+                }
+            }
+            catch (Exception)
+            {
+                Close();
+            }
+        }
+
+        private void SendControl(WebSocketOpcode opcode, ReadOnlySpan<byte> payload)
+        {
+            if (_closed)
+            {
+                return;
+            }
+
+            var frame = WebSocketProtocol.EncodeFrame(payload, opcode);
+            try
+            {
+                lock (_sendLock)
+                {
+                    _stream.Write(frame, 0, frame.Length);
+                }
+            }
+            catch (Exception)
+            {
+                Close();
+            }
+        }
+
+        public bool TryReceive(out byte[] message) => _inbox.TryDequeue(out message!);
+
+        public void Close()
+        {
+            if (_closed)
+            {
+                return;
+            }
+
+            _closed = true;
+            try
+            {
+                _client.Dispose();
+            }
+            catch (Exception)
+            {
+                // соединение уже мертво — закрытие не должно бросать
+            }
+        }
+
+        private void ReceiveLoop()
+        {
+            var pending = new List<byte>();
+            var pendingOpcode = WebSocketOpcode.Binary;
+            try
+            {
+                while (!_closed)
+                {
+                    if (
+                        !WebSocketProtocol.TryReadFrame(
+                            _stream,
+                            out var opcode,
+                            out var fin,
+                            out var payload
+                        )
+                    )
+                    {
+                        break;
+                    }
+
+                    // Любой кадр (включая pong) — признак жизни: сбрасываем счётчик простоя.
+                    Volatile.Write(ref _lastActivityTicks, DateTime.UtcNow.Ticks);
+
+                    switch (opcode)
+                    {
+                        case WebSocketOpcode.Ping:
+                            SendControl(WebSocketOpcode.Pong, payload);
+                            continue;
+                        case WebSocketOpcode.Pong:
+                            continue;
+                        case WebSocketOpcode.Close:
+                            SendControl(WebSocketOpcode.Close, []);
+                            return;
+                    }
+
+                    if (opcode != WebSocketOpcode.Continuation)
+                    {
+                        pendingOpcode = opcode;
+                        pending.Clear();
+                    }
+
+                    if (pending.Count + payload.Length > MaxMessageBytes)
+                    {
+                        Log.Warning(
+                            $"WebSocketServer: connection #{Id} exceeded {MaxMessageBytes}-byte "
+                                + "message cap — closing"
+                        );
+                        return; // finally закроет соединение
+                    }
+
+                    pending.AddRange(payload);
+                    if (fin && pendingOpcode == WebSocketOpcode.Binary)
+                    {
+                        _inbox.Enqueue(pending.ToArray());
+                        pending.Clear();
+                    }
+                }
+            }
+            catch (Exception)
+            {
+                // обрыв соединения — штатный путь завершения цикла
+            }
+            finally
+            {
+                Close();
+            }
+        }
+    }
+}

src/MrGameEng.Simulation/AI/Suitability.cs

@@ -0,0 +1,63 @@
+namespace MrGameEng.AI;
+
+/// <summary>
+/// Suitability curves: how well an environmental value matches a preferred optimum. Unlike
+/// <see cref="ResponseCurve"/> (monotonic shaping over <c>[0,1]</c>), these are bell shapes around an
+/// optimum on an arbitrary scale — the building block for "this organism likes ~18°C, tolerates ±12°".
+/// Pure and GPU-free.
+/// </summary>
+public static class Suitability
+{
+    /// <summary>
+    /// Gaussian bell in <c>[0, 1]</c>: 1 when <paramref name="value"/> equals <paramref name="optimum"/>,
+    /// falling off as it departs, reaching <c>e^-0.5 ≈ 0.607</c> one <paramref name="tolerance"/> away.
+    /// A non-positive <paramref name="tolerance"/> degenerates to an exact match (1 at the optimum, else 0).
+    /// </summary>
+    public static float Gaussian(float value, float optimum, float tolerance)
+    {
+        if (tolerance <= 0f)
+        {
+            return value == optimum ? 1f : 0f;
+        }
+
+        var z = (value - optimum) / tolerance;
+        return MathF.Exp(-0.5f * z * z);
+    }
+
+    /// <summary>
+    /// Trapezoidal suitability in <c>[0, 1]</c>: <c>0</c> at or beyond the hard limits
+    /// <paramref name="min"/>/<paramref name="max"/>, ramping linearly up to <c>1</c> at
+    /// <paramref name="optimalLow"/>, flat <c>1</c> across the comfortable plateau to
+    /// <paramref name="optimalHigh"/>, then ramping back down to <c>0</c> at <paramref name="max"/>.
+    /// Models a hard tolerance band with a plateau (RimWorld-style plant growth vs. temperature:
+    /// dormant below <paramref name="min"/> or above <paramref name="max"/>). A degenerate edge
+    /// (<paramref name="optimalLow"/> ≤ <paramref name="min"/> or <paramref name="optimalHigh"/> ≥
+    /// <paramref name="max"/>) becomes a hard step on that side. The four bounds are expected
+    /// ordered (<c>min ≤ optimalLow ≤ optimalHigh ≤ max</c>); pass ordered values.
+    /// </summary>
+    public static float Trapezoid(
+        float value,
+        float min,
+        float optimalLow,
+        float optimalHigh,
+        float max
+    )
+    {
+        if (value <= min || value >= max)
+        {
+            return 0f;
+        }
+
+        if (value < optimalLow)
+        {
+            return optimalLow > min ? (value - min) / (optimalLow - min) : 1f;
+        }
+
+        if (value > optimalHigh)
+        {
+            return max > optimalHigh ? (max - value) / (max - optimalHigh) : 1f;
+        }
+
+        return 1f;
+    }
+}

tests/MrGameEng.Content.Tests/Genetics/GeneDefLoadTests.cs

@@ -0,0 +1,68 @@
+using MrGameEng.Genetics;
+using MrGameEng.Mods;
+using Xunit;
+
+namespace MrGameEng.Genetics.Tests;
+
+/// <summary>
+/// Verifies <see cref="GeneDef"/> loads through the real <see cref="DefDatabase"/> the way the game
+/// loads <c>genes.json</c>: string-named <see cref="GeneKind"/>, parent inheritance and effect maps.
+/// </summary>
+public sealed class GeneDefLoadTests : IDisposable
+{
+    private readonly string _root = Directory.CreateTempSubdirectory("mrge-gene-tests-").FullName;
+
+    public void Dispose() => Directory.Delete(_root, recursive: true);
+
+    private DefDatabase Load(string defsJson)
+    {
+        var modDir = Path.Combine(_root, "mod");
+        Directory.CreateDirectory(Path.Combine(modDir, "Defs"));
+        File.WriteAllText(Path.Combine(modDir, "Defs", "genes.json"), defsJson);
+        var database = new DefDatabase();
+        database.RegisterType<GeneDef>("Gene");
+        database.Load([new Mod(new ModInfo { Id = "mod" }, modDir)]);
+        return database;
+    }
+
+    [Fact]
+    public void Load_NumericGeneWithParentAndEffects_Resolves()
+    {
+        var database = Load(
+            """
+            { "type": "Gene", "defs": [
+                { "defName": "BaseGene", "abstract": true, "spread": 0.1, "mutationChance": 0.05 },
+                { "defName": "GeneVigor", "parent": "BaseGene", "default": 1.0, "min": 0.1, "max": 3.0,
+                  "tags": ["growth"], "effects": { "vigor": "value" } }
+            ]}
+            """
+        );
+
+        var gene = database.Get<GeneDef>("GeneVigor");
+        Assert.Equal(GeneKind.Numeric, gene.Kind);
+        Assert.Equal(0.1f, gene.Spread); // inherited from parent
+        Assert.Equal(0.05f, gene.MutationChance); // inherited
+        Assert.Equal(3.0f, gene.Max);
+        Assert.Equal(["growth"], gene.Tags);
+        Assert.Equal("value", gene.Effects["vigor"]);
+        Assert.Single(gene.CompiledEffects); // formula compiles
+    }
+
+    [Fact]
+    public void Load_DiscreteKindByName_Parses()
+    {
+        var database = Load(
+            """
+            { "type": "Gene", "defs": [
+                { "defName": "GeneMorph", "kind": "Discrete", "variants": 2,
+                  "variantWeights": [0.8, 0.2], "effects": { "variant": "value" } }
+            ]}
+            """
+        );
+
+        var gene = database.Get<GeneDef>("GeneMorph");
+        Assert.Equal(GeneKind.Discrete, gene.Kind);
+        Assert.Equal(2, gene.Variants);
+        Assert.Equal([0.8f, 0.2f], gene.VariantWeights);
+    }
+}

tests/MrGameEng.Content.Tests/Genetics/GeneticsTests.cs

@@ -0,0 +1,194 @@
+using MrGameEng.Formulas;
+using MrGameEng.Genetics;
+using Xunit;
+
+namespace MrGameEng.Genetics.Tests;
+
+public class GeneticsTests
+{
+    private static GeneDef Numeric(
+        string name,
+        float def,
+        float spread = 0f,
+        float min = float.NegativeInfinity,
+        float max = float.PositiveInfinity,
+        float mutationChance = 0f,
+        float mutationMagnitude = 0.1f,
+        Dictionary<string, string>? effects = null
+    ) =>
+        new()
+        {
+            DefName = name,
+            Kind = GeneKind.Numeric,
+            Default = def,
+            Spread = spread,
+            Min = min,
+            Max = max,
+            MutationChance = mutationChance,
+            MutationMagnitude = mutationMagnitude,
+            Effects = effects ?? new(),
+        };
+
+    private static GeneDef Discrete(string name, int variants = 2, float mutationChance = 0f) =>
+        new()
+        {
+            DefName = name,
+            Kind = GeneKind.Discrete,
+            Variants = variants,
+            MutationChance = mutationChance,
+        };
+
+    private static Dictionary<string, GeneDef> Registry(params GeneDef[] genes) =>
+        genes.ToDictionary(g => g.DefName, g => g, StringComparer.Ordinal);
+
+    [Fact]
+    public void Generate_NumericAlleles_StayWithinSpreadAndClamp()
+    {
+        var gene = Numeric("vigor", def: 1f, spread: 0.2f, min: 0f, max: 2f);
+        var random = new Random(7);
+
+        for (var i = 0; i < 200; i++)
+        {
+            var genome = Genome.Generate([gene], random);
+            var allele = genome["vigor"];
+            Assert.InRange(allele.A, 0.8f, 1.2f);
+            Assert.InRange(allele.B, 0.8f, 1.2f);
+        }
+    }
+
+    [Fact]
+    public void Generate_SameSeed_IsDeterministic()
+    {
+        var genes = new[] { Numeric("a", 1f, 0.3f), Discrete("morph", 2) };
+
+        var first = Genome.Generate(genes, new Random(42));
+        var second = Genome.Generate(genes, new Random(42));
+
+        Assert.Equal(first["a"], second["a"]);
+        Assert.Equal(first["morph"], second["morph"]);
+    }
+
+    [Fact]
+    public void Express_Numeric_IsAlleleMean()
+    {
+        var gene = Numeric("opt", 0f);
+        var genome = new Genome { ["opt"] = new Allele(0.4f, 0.8f) };
+
+        Assert.Equal(0.6f, genome.Express(gene), 5);
+    }
+
+    [Fact]
+    public void Express_Discrete_DominantIsLowerIndex()
+    {
+        var gene = Discrete("morph", 2);
+
+        Assert.Equal(0f, new Genome { ["morph"] = new Allele(0f, 1f) }.Express(gene)); // heterozygous → dominant 0
+        Assert.Equal(1f, new Genome { ["morph"] = new Allele(1f, 1f) }.Express(gene)); // homozygous recessive
+    }
+
+    [Fact]
+    public void Breed_WithoutMutation_InheritsOneAlleleFromEachParent()
+    {
+        var gene = Numeric("g", 0f, mutationChance: 0f);
+        var registry = Registry(gene);
+        var a = new Genome { ["g"] = new Allele(1f, 2f) };
+        var b = new Genome { ["g"] = new Allele(3f, 4f) };
+
+        var child = Genome.Breed(a, b, registry, new Random(1));
+
+        Assert.Contains(child["g"].A, new[] { 1f, 2f }); // first allele from parent a
+        Assert.Contains(child["g"].B, new[] { 3f, 4f }); // second allele from parent b
+    }
+
+    [Fact]
+    public void Breed_UnionOfGenes_ProducesHybridComposition()
+    {
+        // a carries only "leaf", b carries only "root" — a child can carry both (hybrid).
+        var registry = Registry(Numeric("leaf", 1f), Numeric("root", 1f));
+        var a = new Genome { ["leaf"] = new Allele(1f, 1f) };
+        var b = new Genome { ["root"] = new Allele(2f, 2f) };
+
+        var carriedBoth = false;
+        for (var seed = 0; seed < 50 && !carriedBoth; seed++)
+        {
+            var child = Genome.Breed(a, b, registry, new Random(seed));
+            carriedBoth = child.Has("leaf") && child.Has("root");
+        }
+
+        Assert.True(carriedBoth, "single-parent genes should sometimes both be inherited");
+    }
+
+    [Fact]
+    public void Breed_HighMutation_DiscreteCanFlipVariant()
+    {
+        var gene = Discrete("morph", variants: 2, mutationChance: 1f);
+        var registry = Registry(gene);
+        var parent = new Genome { ["morph"] = new Allele(0f, 0f) };
+
+        var sawOne = false;
+        for (var seed = 0; seed < 50 && !sawOne; seed++)
+        {
+            var child = Genome.Breed(parent, parent, registry, new Random(seed));
+            var allele = child["morph"];
+            sawOne = allele.A == 1f || allele.B == 1f;
+        }
+
+        Assert.True(sawOne, "with full mutation a 0/0 parent should sometimes yield variant 1");
+    }
+
+    [Fact]
+    public void Compute_GeneEffect_UsesValueVariable()
+    {
+        var gene = Numeric("vigor", 0f, effects: new() { ["growth"] = "value * 2" });
+        var genome = new Genome { ["vigor"] = new Allele(1.5f, 2.5f) }; // mean 2
+
+        var traits = Phenotype.Compute(genome, Registry(gene));
+
+        Assert.Equal(4f, traits["growth"], 5); // 2 * 2
+    }
+
+    [Fact]
+    public void Compute_MultipleGenes_SumContributionsPerTrait()
+    {
+        var a = Numeric("a", 0f, effects: new() { ["yield"] = "value" });
+        var b = Numeric("b", 0f, effects: new() { ["yield"] = "value" });
+        var genome = new Genome { ["a"] = new Allele(3f, 3f), ["b"] = new Allele(4f, 4f) };
+
+        var traits = Phenotype.Compute(genome, Registry(a, b));
+
+        Assert.Equal(7f, traits["yield"], 5);
+    }
+
+    [Fact]
+    public void Compute_FormulaReadsEnvironmentAndOtherGenes()
+    {
+        var opt = Numeric("optLight", 0.5f);
+        var vigor = Numeric(
+            "vigor",
+            1f,
+            effects: new() { ["rate"] = "value * (1 - abs(light - optLight))" }
+        );
+        var genome = new Genome
+        {
+            ["optLight"] = new Allele(0.5f, 0.5f),
+            ["vigor"] = new Allele(1f, 1f),
+        };
+        var env = new DelegateFormulaContext(n =>
+            n == "light" ? 0.7f : throw new FormulaException(n)
+        );
+
+        var traits = Phenotype.Compute(genome, Registry(opt, vigor), env);
+
+        Assert.Equal(0.8f, traits["rate"], 5); // 1 * (1 - |0.7 - 0.5|)
+    }
+
+    [Fact]
+    public void CompiledEffects_InvalidFormula_ThrowsWithGeneAndTrait()
+    {
+        var gene = Numeric("bad", 0f, effects: new() { ["t"] = "value *" });
+
+        var error = Assert.Throws<InvalidDataException>(() => _ = gene.CompiledEffects);
+        Assert.Contains("bad", error.Message);
+        Assert.Contains("t", error.Message);
+    }
+}

tests/MrGameEng.Content.Tests/Genetics/GenomeTemplateTests.cs

@@ -0,0 +1,106 @@
+using MrGameEng.Genetics;
+using Xunit;
+
+namespace MrGameEng.Genetics.Tests;
+
+public class GenomeTemplateTests
+{
+    private static GeneDef Numeric(string name, float min, float max) =>
+        new()
+        {
+            DefName = name,
+            Kind = GeneKind.Numeric,
+            Min = min,
+            Max = max,
+        };
+
+    private static GeneDef Discrete(string name, int variants = 2) =>
+        new()
+        {
+            DefName = name,
+            Kind = GeneKind.Discrete,
+            Variants = variants,
+        };
+
+    [Fact]
+    public void Generate_UsesPerEntryBaseAndSpread_NotGeneDefault()
+    {
+        var gene = Numeric("opt", min: 0f, max: 100f); // GeneDef.Default is 0
+        var template = new GenomeTemplate([
+            new GenomeTemplate.Entry(gene, Base: 50f, Spread: 0.1f),
+        ]);
+        var random = new Random(3);
+
+        for (var i = 0; i < 200; i++)
+        {
+            var allele = template.Generate(random)["opt"];
+            Assert.InRange(allele.A, 45f, 55f); // around the template base, not 0
+            Assert.InRange(allele.B, 45f, 55f);
+        }
+    }
+
+    [Fact]
+    public void Generate_TwoSpecies_DifferInCentre()
+    {
+        var gene = Numeric("opt", 0f, 100f);
+        var oak = new GenomeTemplate([new GenomeTemplate.Entry(gene, 20f, 0f)]);
+        var grass = new GenomeTemplate([new GenomeTemplate.Entry(gene, 80f, 0f)]);
+
+        Assert.Equal(20f, oak.Generate(new Random(1)).Express(gene), 3);
+        Assert.Equal(80f, grass.Generate(new Random(1)).Express(gene), 3);
+    }
+
+    [Fact]
+    public void Registry_CoversEntries_AndDrivesBreeding()
+    {
+        var template = new GenomeTemplate([
+            new GenomeTemplate.Entry(Numeric("a", 0f, 10f), 5f, 0.1f),
+            new GenomeTemplate.Entry(Discrete("morph"), 0f, 0f),
+        ]);
+        var random = new Random(9);
+        var a = template.Generate(random);
+        var b = template.Generate(random);
+
+        var child = Genome.Breed(a, b, template.Registry, random);
+
+        Assert.True(child.Has("a"));
+        Assert.True(child.Has("morph"));
+    }
+
+    [Fact]
+    public void Breed_MutationChanceOverride_ForcesMutation()
+    {
+        var gene = Numeric("a", min: -100f, max: 100f);
+        var registry = new Dictionary<string, GeneDef> { ["a"] = gene };
+        var parent = new Genome { ["a"] = new Allele(10f, 10f) };
+
+        // Override chance to 1 → every inherited allele mutates away from 10.
+        var moved = false;
+        for (var seed = 0; seed < 30 && !moved; seed++)
+        {
+            var child = Genome.Breed(
+                parent,
+                parent,
+                registry,
+                new Random(seed),
+                mutationChance: 1f
+            );
+            moved = child["a"].A != 10f || child["a"].B != 10f;
+        }
+
+        Assert.True(moved, "with overridden mutationChance=1 the allele should mutate");
+    }
+
+    [Fact]
+    public void Breed_MutationChanceZero_KeepsAlleles()
+    {
+        var gene = Numeric("a", -100f, 100f);
+        var registry = new Dictionary<string, GeneDef> { ["a"] = gene };
+        var parent = new Genome { ["a"] = new Allele(10f, 10f) };
+
+        var child = Genome.Breed(parent, parent, registry, new Random(5), mutationChance: 0f);
+
+        Assert.Equal(10f, child["a"].A);
+        Assert.Equal(10f, child["a"].B);
+    }
+}

tests/MrGameEng.Content.Tests/Mods/DefDatabaseTests.cs

@@ -143,4 +143,73 @@ public sealed class DefDatabaseTests : IDisposable
         Assert.Throws<KeyNotFoundException>(() => database.Get<AnimalDef>("Dodo"));
         Assert.False(database.TryGet<AnimalDef>("Dodo", out _));
     }
+
+    private Mod WriteMod(string fileName, string json)
+    {
+        var id = $"mod{_modCounter++:D2}";
+        var modDir = Path.Combine(_root, id);
+        Directory.CreateDirectory(Path.Combine(modDir, "Defs"));
+        File.WriteAllText(Path.Combine(modDir, "Defs", fileName), json);
+        return new Mod(new ModInfo { Id = id }, modDir);
+    }
+
+    [Fact]
+    public void Patch_SetsFields_OnDefsMatchingNamePattern()
+    {
+        var defs = WriteDefsMod(
+            """
+            { "type": "Animal", "defs": [
+                { "defName": "Wolf", "speed": 9 },
+                { "defName": "WolfPup", "speed": 4 },
+                { "defName": "Bear", "speed": 6 }
+            ]}
+            """
+        );
+        var patch = WriteMod(
+            "patches.json",
+            """{ "type": "Patch", "patches": [ { "defType": "Animal", "match": "Wolf.*", "set": { "legs": 6 } } ] }"""
+        );
+
+        var database = LoadAnimals(defs, patch);
+
+        Assert.Equal(6, database.Get<AnimalDef>("Wolf").Legs); // matched
+        Assert.Equal(6, database.Get<AnimalDef>("WolfPup").Legs); // matched
+        Assert.Equal(4, database.Get<AnimalDef>("Bear").Legs); // unmatched → default
+    }
+
+    [Fact]
+    public void Patch_UnknownDefType_Throws()
+    {
+        var patch = WriteMod(
+            "patches.json",
+            """{ "type": "Patch", "patches": [ { "defType": "Ghost", "match": ".*", "set": {} } ] }"""
+        );
+
+        Assert.Throws<InvalidDataException>(() => LoadAnimals(patch));
+    }
+
+    [Fact]
+    public void Validator_RejectsField_NotMatchingPattern()
+    {
+        var database = new DefDatabase();
+        database.RegisterType<AnimalDef>("Animal");
+        database.RegisterValidator("Animal", "defName", "^[A-Z]");
+        var bad = WriteDefsMod("""{ "type": "Animal", "defs": [ { "defName": "wolf" } ] }""");
+
+        var error = Assert.Throws<InvalidDataException>(() => database.Load([bad]));
+        Assert.Contains("wolf", error.Message);
+    }
+
+    [Fact]
+    public void Validator_Passes_WhenFieldMatches()
+    {
+        var database = new DefDatabase();
+        database.RegisterType<AnimalDef>("Animal");
+        database.RegisterValidator("Animal", "defName", "^[A-Z]");
+        database.Load([
+            WriteDefsMod("""{ "type": "Animal", "defs": [ { "defName": "Wolf", "speed": 7 } ] }"""),
+        ]);
+
+        Assert.Equal(7f, database.Get<AnimalDef>("Wolf").Speed);
+    }
 }

tests/MrGameEng.Core.Tests/CalendarTests.cs

@@ -41,6 +41,33 @@ public class CalendarTests
         Assert.Equal(0.5f, calendar.DayProgress, 5);
     }
 
+    [Fact]
+    public void HourAndMinute_DecomposeTimeOfDay()
+    {
+        var clock = new GameClock();
+        var calendar = new Calendar(clock, secondsPerDay: 1440f); // one minute per in-game minute
+
+        clock.Advance(14 * 60 + 30); // 14:30
+
+        Assert.Equal(14, calendar.Hour);
+        Assert.Equal(30, calendar.Minute);
+        Assert.Equal(14 * 60 + 30, calendar.MinuteOfDay);
+    }
+
+    [Fact]
+    public void StartDay_OffsetsTheTimeOfDay()
+    {
+        var clock = new GameClock();
+        var calendar = new Calendar(clock, secondsPerDay: 10f, startDay: 7.0 / 24); // begin at 07:00
+
+        Assert.Equal(1, calendar.Day);
+        Assert.Equal(7, calendar.Hour);
+        Assert.Equal(0, calendar.Minute);
+
+        clock.Advance(5f); // half a day later → 19:00
+        Assert.Equal(19, calendar.Hour);
+    }
+
     [Fact]
     public void Pause_DoesNotAdvanceTheCalendar()
     {

tests/MrGameEng.Core.Tests/ClimateTests.cs

@@ -0,0 +1,95 @@
+using MrGameEng.Core;
+using Xunit;
+
+namespace MrGameEng.Core.Tests;
+
+public class ClimateTests
+{
+    private static (GameClock Clock, Climate Climate) Make(ClimateSettings settings)
+    {
+        var clock = new GameClock();
+        var calendar = new Calendar(clock, secondsPerDay: 10f);
+        return (clock, new Climate(calendar, settings));
+    }
+
+    private static ClimateSettings Seasonal =>
+        new()
+        {
+            DaysPerYear = 60,
+            MeanTemperature = 10f,
+            SeasonalAmplitude = 20f,
+            DailyAmplitude = 0f,
+            WarmestDay = 15,
+        };
+
+    [Fact]
+    public void Constructor_NonPositiveYear_Throws()
+    {
+        Assert.Throws<ArgumentOutOfRangeException>(() =>
+            new Climate(new Calendar(new GameClock(), 10f), Seasonal with { DaysPerYear = 0 })
+        );
+    }
+
+    [Fact]
+    public void Temperature_PeaksOnWarmestDay_AndBottomsHalfYearLater()
+    {
+        var (clock, climate) = Make(Seasonal);
+
+        clock.Advance(15 * 10f); // day 15 = warmest
+        Assert.Equal(30f, climate.Temperature, 2); // mean 10 + amplitude 20
+
+        clock.Advance(30 * 10f); // +30 days = half a 60-day year later
+        Assert.Equal(-10f, climate.Temperature, 2); // mean 10 - amplitude 20
+    }
+
+    [Fact]
+    public void DailySwing_WarmerAtNoonThanMidnight()
+    {
+        var settings = Seasonal with { SeasonalAmplitude = 0f, DailyAmplitude = 6f };
+        var (clock, climate) = Make(settings);
+
+        clock.Advance(5f); // day 0, noon (DayProgress 0.5)
+        Assert.Equal(16f, climate.Temperature, 2); // mean 10 + daily 6
+
+        clock.Advance(5f); // day 1, midnight (DayProgress 0)
+        Assert.Equal(4f, climate.Temperature, 2); // mean 10 - daily 6
+    }
+
+    [Fact]
+    public void Season_FollowsTheQuarterOfTheYear()
+    {
+        var (clock, climate) = Make(Seasonal); // 60-day year → 15 days per season
+
+        Assert.Equal(Season.Spring, climate.Season);
+        clock.Advance(20 * 10f);
+        Assert.Equal(Season.Summer, climate.Season);
+        clock.Advance(15 * 10f);
+        Assert.Equal(Season.Autumn, climate.Season);
+        clock.Advance(15 * 10f);
+        Assert.Equal(Season.Winter, climate.Season);
+    }
+
+    [Fact]
+    public void YearAndDayOfYear_RollOver()
+    {
+        var (clock, climate) = Make(Seasonal);
+
+        Assert.Equal(1, climate.Year);
+        Assert.Equal(0, climate.DayOfYear);
+
+        clock.Advance(60 * 10f); // exactly one year
+        Assert.Equal(2, climate.Year);
+        Assert.Equal(0, climate.DayOfYear);
+    }
+
+    [Fact]
+    public void StartDayOfYear_ShiftsTheSeasonalPhase()
+    {
+        // Begin the world already at the warmest day (15): the curve peaks at clock 0.
+        var (_, climate) = Make(Seasonal with { StartDayOfYear = 15 });
+
+        Assert.Equal(30f, climate.Temperature, 2); // mean 10 + amplitude 20, at the peak
+        Assert.Equal(15, climate.DayOfYear); // day-of-year reflects the offset
+        Assert.Equal(Season.Summer, climate.Season); // day 15 of a 60-day year = start of summer
+    }
+}

tests/MrGameEng.Core.Tests/FormulaTests.cs

@@ -0,0 +1,174 @@
+using MrGameEng.Formulas;
+using Xunit;
+
+namespace MrGameEng.Core.Tests;
+
+public class FormulaTests
+{
+    private static IFormulaContext Vars(Dictionary<string, float> values) =>
+        new DelegateFormulaContext(name =>
+            values.TryGetValue(name, out var v)
+                ? v
+                : throw new FormulaException($"unknown '{name}'")
+        );
+
+    [Theory]
+    [InlineData("1 + 2 * 3", 7f)] // precedence
+    [InlineData("(1 + 2) * 3", 9f)] // parentheses
+    [InlineData("10 - 2 - 3", 5f)] // left associativity
+    [InlineData("-2 + 5", 3f)] // unary minus
+    [InlineData("2 * -3", -6f)] // unary minus after operator
+    [InlineData("7 % 3", 1f)] // modulo
+    [InlineData("2.5 * 4", 10f)] // decimals
+    public void Evaluate_Arithmetic_RespectsPrecedence(string expr, float expected)
+    {
+        Assert.Equal(expected, Formula.Compile(expr).Evaluate(), 4);
+    }
+
+    [Theory]
+    [InlineData("min(3, 5)", 3f)]
+    [InlineData("max(3, 5)", 5f)]
+    [InlineData("clamp(12, 0, 10)", 10f)]
+    [InlineData("clamp(-4, 0, 10)", 0f)]
+    [InlineData("lerp(0, 10, 0.25)", 2.5f)]
+    [InlineData("pow(2, 10)", 1024f)]
+    [InlineData("abs(-7)", 7f)]
+    [InlineData("floor(3.9)", 3f)]
+    [InlineData("ceil(3.1)", 4f)]
+    [InlineData("step(5, 7)", 1f)]
+    [InlineData("step(5, 2)", 0f)]
+    public void Evaluate_Functions_ComputeExpected(string expr, float expected)
+    {
+        Assert.Equal(expected, Formula.Compile(expr).Evaluate(), 4);
+    }
+
+    [Fact]
+    public void Evaluate_Constants_AreBuiltIn()
+    {
+        Assert.Equal(MathF.PI, Formula.Compile("pi").Evaluate(), 5);
+        Assert.Equal(MathF.Tau, Formula.Compile("tau").Evaluate(), 5);
+        Assert.Equal(MathF.E, Formula.Compile("e").Evaluate(), 5);
+    }
+
+    [Theory]
+    [InlineData("2 < 3", 1f)]
+    [InlineData("3 <= 3", 1f)]
+    [InlineData("3 > 5", 0f)]
+    [InlineData("4 == 4", 1f)]
+    [InlineData("4 != 4", 0f)]
+    [InlineData("1 && 0", 0f)]
+    [InlineData("0 || 2", 1f)]
+    [InlineData("!0", 1f)]
+    [InlineData("!5", 0f)]
+    public void Evaluate_LogicAndComparison_YieldBooleansAsOneOrZero(string expr, float expected)
+    {
+        Assert.Equal(expected, Formula.Compile(expr).Evaluate(), 4);
+    }
+
+    [Theory]
+    [InlineData("3 > 2 ? 10 : 20", 10f)]
+    [InlineData("3 < 2 ? 10 : 20", 20f)]
+    [InlineData("1 ? 2 ? 3 : 4 : 5", 3f)] // nested ternary
+    public void Evaluate_Ternary_SelectsBranch(string expr, float expected)
+    {
+        Assert.Equal(expected, Formula.Compile(expr).Evaluate(), 4);
+    }
+
+    [Fact]
+    public void Evaluate_Variables_ResolvedThroughContext()
+    {
+        var ctx = Vars(new() { ["light"] = 0.8f, ["optimal"] = 0.5f });
+        var formula = Formula.Compile("clamp(1 - abs(light - optimal), 0, 1)");
+        Assert.Equal(0.7f, formula.Evaluate(ctx), 4);
+    }
+
+    [Fact]
+    public void Evaluate_SameFormulaTwice_IsDeterministic()
+    {
+        var formula = Formula.Compile("sin(t) * 2 + 1");
+        var ctx = Vars(new() { ["t"] = 1.234f });
+        Assert.Equal(formula.Evaluate(ctx), formula.Evaluate(ctx), 6);
+    }
+
+    [Theory]
+    [InlineData("1 +")] // dangling operator
+    [InlineData("(1 + 2")] // unbalanced paren
+    [InlineData("1 2")] // trailing token
+    [InlineData("min(1)")] // wrong arity
+    [InlineData("nope(1)")] // unknown function
+    [InlineData("@")] // bad character
+    [InlineData("1 = 2")] // single equals
+    public void Compile_InvalidExpression_Throws(string expr)
+    {
+        Assert.Throws<FormulaException>(() => Formula.Compile(expr));
+    }
+
+    [Fact]
+    public void Evaluate_UnknownVariableWithoutContext_Throws()
+    {
+        var formula = Formula.Compile("x + 1");
+        Assert.Throws<FormulaException>(() => formula.Evaluate());
+    }
+
+    // --- Group functions (regex aggregation over matching variables) ---
+
+    private sealed class GroupContext(Dictionary<string, float> values) : IFormulaContext
+    {
+        public float Resolve(string name) => values[name];
+
+        public IEnumerable<float> ResolveMatching(Func<string, bool> matches)
+        {
+            foreach (var (name, value) in values)
+            {
+                if (matches(name))
+                {
+                    yield return value;
+                }
+            }
+        }
+    }
+
+    [Fact]
+    public void Evaluate_GroupFunctions_AggregateMatchingVariables()
+    {
+        var ctx = new GroupContext(
+            new()
+            {
+                ["leaf_a"] = 2f,
+                ["leaf_b"] = 4f,
+                ["leaf_c"] = 6f,
+                ["root_a"] = 100f,
+            }
+        );
+
+        Assert.Equal(12f, Formula.Compile("gsum('leaf_.*')").Evaluate(ctx), 4); // 2+4+6
+        Assert.Equal(3f, Formula.Compile("gcount('leaf_.*')").Evaluate(ctx), 4);
+        Assert.Equal(4f, Formula.Compile("gavg('leaf_.*')").Evaluate(ctx), 4);
+        Assert.Equal(2f, Formula.Compile("gmin('leaf_.*')").Evaluate(ctx), 4);
+        Assert.Equal(6f, Formula.Compile("gmax('leaf_.*')").Evaluate(ctx), 4);
+    }
+
+    [Fact]
+    public void Evaluate_GroupFunction_ComposesWithArithmetic()
+    {
+        var ctx = new GroupContext(new() { ["g1"] = 3f, ["g2"] = 5f });
+        Assert.Equal(16f, Formula.Compile("gsum('g.*') * 2").Evaluate(ctx), 4); // (3+5)*2
+    }
+
+    [Fact]
+    public void Evaluate_GroupFunction_NoMatches_IsZero()
+    {
+        var ctx = new GroupContext(new() { ["x"] = 1f });
+        Assert.Equal(0f, Formula.Compile("gsum('none_.*')").Evaluate(ctx), 4);
+        Assert.Equal(0f, Formula.Compile("gavg('none_.*')").Evaluate(ctx), 4);
+    }
+
+    [Theory]
+    [InlineData("gsum(leaf)")] // pattern must be a quoted string
+    [InlineData("gsum('[')")] // invalid regex
+    [InlineData("gsum('a' 'b')")] // extra token
+    public void Compile_BadGroupCall_Throws(string expr)
+    {
+        Assert.Throws<FormulaException>(() => Formula.Compile(expr));
+    }
+}

tests/MrGameEng.Core.Tests/HeadlessHostTests.cs

@@ -0,0 +1,117 @@
+using MrGameEng.Core;
+using Xunit;
+
+namespace MrGameEng.Core.Tests;
+
+public class HeadlessHostTests
+{
+    private sealed class CountingScene : Scene
+    {
+        public int LoadCount;
+        public int UnloadCount;
+        public int UpdateCount;
+
+        protected override void OnLoad() => LoadCount++;
+
+        protected override void OnUnload() => UnloadCount++;
+
+        public override void Update(GameClock clock)
+        {
+            UpdateCount++;
+            base.Update(clock);
+        }
+    }
+
+    [Fact]
+    public void RunTicks_AdvancesClock_ByExactFixedStep()
+    {
+        var scene = new CountingScene();
+        using var host = new HeadlessHost(new HeadlessHostOptions { TicksPerSecond = 10f }, scene);
+
+        host.RunTicks(30);
+
+        Assert.Equal(0.1f, host.FixedDeltaTime, 3);
+        Assert.Equal(30, host.TickCount);
+        Assert.Equal(3.0, host.Context.Clock.TotalTime, 3);
+        Assert.Equal(30, scene.UpdateCount);
+    }
+
+    [Fact]
+    public void FirstTick_LoadsTheInitialScene()
+    {
+        var scene = new CountingScene();
+        using var host = new HeadlessHost(new HeadlessHostOptions(), scene);
+
+        Assert.Equal(0, scene.LoadCount);
+
+        host.Tick();
+
+        Assert.Equal(1, scene.LoadCount);
+        Assert.Same(scene, host.Context.Scenes.Current);
+    }
+
+    [Fact]
+    public void Dispose_UnloadsTheActiveScene()
+    {
+        var scene = new CountingScene();
+        var host = new HeadlessHost(new HeadlessHostOptions(), scene);
+        host.Tick();
+
+        host.Dispose();
+
+        Assert.Equal(1, scene.UnloadCount);
+        Assert.Null(host.Context.Scenes.Current);
+    }
+
+    [Fact]
+    public void Run_StopsWhenCancelled()
+    {
+        using var cancellation = new CancellationTokenSource();
+        var scene = new CancellingScene(cancellation, afterTicks: 5);
+        using var host = new HeadlessHost(new HeadlessHostOptions { Realtime = false }, scene);
+
+        host.Run(cancellation.Token);
+
+        Assert.Equal(5, scene.UpdateCount);
+    }
+
+    [Fact]
+    public void TimeScale_StillApplies_OnTopOfFixedStep()
+    {
+        var scene = new CountingScene();
+        using var host = new HeadlessHost(new HeadlessHostOptions { TicksPerSecond = 10f }, scene);
+        host.Context.Clock.TimeScale = 3f;
+
+        host.RunTicks(10);
+
+        Assert.Equal(3.0, host.Context.Clock.TotalTime, 3);
+        Assert.Equal(1.0, host.Context.Clock.UnscaledTotalTime, 3);
+    }
+
+    [Fact]
+    public void NonPositiveTickRate_Throws()
+    {
+        Assert.Throws<ArgumentOutOfRangeException>(() =>
+            new HeadlessHost(new HeadlessHostOptions { TicksPerSecond = 0f }, new CountingScene())
+        );
+    }
+
+    private sealed class CancellingScene(CancellationTokenSource cancellation, int afterTicks)
+        : Scene
+    {
+        public int UpdateCount;
+
+        protected override void OnLoad() { }
+
+        public override void Update(GameClock clock)
+        {
+            UpdateCount++;
+            if (UpdateCount >= afterTicks)
+            {
+                cancellation.Cancel();
+            }
+
+            base.Update(clock);
+        }
+    }
+}

tests/MrGameEng.Core.Tests/SceneTransitionTests.cs

@@ -15,6 +15,14 @@ public class SceneTransitionTests
         protected override void OnUnload() => UnloadCount++;
     }
 
+    // Тайминг-машина живёт в ядре и не зависит от визуала перехода —
+    // тестируем на голой заглушке с длительностями, как у Fade.
+    private sealed class TimedTransition(float outDuration, float inDuration)
+        : Transition(outDuration, inDuration);
+
+    private static Transition Fade(float duration) =>
+        new TimedTransition(duration / 2f, duration / 2f);
+
     private static void Tick(EngineContext context, float seconds)
     {
         context.Clock.Advance(seconds);
@@ -31,7 +39,7 @@ public class SceneTransitionTests
         Tick(context, 0.016f);
 
         // Fade(1.0) → фаза закрытия 0.5 c, фаза открытия 0.5 c.
-        context.Scenes.Switch(second, Transition.Fade(1f));
+        context.Scenes.Switch(second, Fade(1f));
         Tick(context, 0.2f);
 
         Assert.True(context.Scenes.IsTransitioning);
@@ -61,7 +69,7 @@ public class SceneTransitionTests
         Tick(context, 0.016f);
         context.Clock.TimeScale = 0f; // игра на паузе
 
-        context.Scenes.Switch(second, Transition.Fade(0.2f));
+        context.Scenes.Switch(second, Fade(0.2f));
         Tick(context, 0.15f);
         Tick(context, 0.15f);
 
@@ -79,7 +87,7 @@ public class SceneTransitionTests
         context.Scenes.Switch(first);
         Tick(context, 0.016f);
 
-        context.Scenes.Switch(second, Transition.Fade(1f));
+        context.Scenes.Switch(second, Fade(1f));
         Tick(context, 0.1f);
         context.Scenes.Switch(third); // передумали, пока экран закрывается
 
@@ -99,12 +107,12 @@ public class SceneTransitionTests
         context.Scenes.Switch(first);
         Tick(context, 0.016f);
 
-        context.Scenes.Switch(second, Transition.Fade(1f)); // 0.5 c закрытие + 0.5 c открытие
+        context.Scenes.Switch(second, Fade(1f)); // 0.5 c закрытие + 0.5 c открытие
         Tick(context, 0.6f); // закрыто, своп на second, началось открытие
         Assert.Same(second, context.Scenes.Current);
 
         Tick(context, 0.25f); // открытие наполовину (coverage ~0.5)
-        context.Scenes.Switch(third, Transition.Fade(1f)); // передумали во время открытия
+        context.Scenes.Switch(third, Fade(1f)); // передумали во время открытия
 
         Tick(context, 0.05f); // экран снова закрывается — свопа ещё нет
         Assert.Same(second, context.Scenes.Current);
@@ -124,7 +132,7 @@ public class SceneTransitionTests
         context.Scenes.Switch(first);
         Tick(context, 0.016f);
 
-        context.Scenes.Switch(second, Transition.Fade(0f));
+        context.Scenes.Switch(second, Fade(0f));
         Tick(context, 0.016f);
         Tick(context, 0.016f);
 

tests/MrGameEng.Graphics.Tests/CameraMathTests.cs

@@ -83,6 +83,29 @@ public class CameraMathTests
         AssertVector(new Vector2(0f, 200f), state.ScreenToWorld(Vector2.Zero));
     }
 
+    [Fact]
+    public void WorldCenter_EqualsUnclampedCameraPosition()
+    {
+        var camera = new Camera(new Vector2(640f, 360f), zoom: 2f);
+
+        var state = CameraMath.Compute(camera, 1280, 720, ViewportMapping.Identity);
+
+        AssertVector(camera.Position, state.WorldCenter);
+    }
+
+    [Fact]
+    public void WorldCenter_ReflectsBoundsClamp_UnlikeRawPosition()
+    {
+        var bounds = new RectF(0f, 0f, 2000f, 1000f);
+        var camera = new Camera(new Vector2(-500f, 500f), bounds: bounds);
+
+        var state = CameraMath.Compute(camera, 800, 600, ViewportMapping.Identity);
+
+        // Raw position is (-500, 500); only X clamps (to half-width 400 from the left world edge),
+        // Y (500) is already inside [300, 700]. The effective centre the view is built around is (400, 500).
+        AssertVector(new Vector2(400f, 500f), state.WorldCenter);
+    }
+
     [Fact]
     public void Mapping_CentersVirtualResolutionInWiderWindow()
     {

tests/MrGameEng.Graphics.Tests/DayNightTests.cs

@@ -0,0 +1,74 @@
+using Microsoft.Xna.Framework;
+using MrGameEng.Core;
+using MrGameEng.Lighting;
+using Xunit;
+
+namespace MrGameEng.Lighting.Tests;
+
+public class DayNightTests
+{
+    private static (GameClock Clock, DayNight DayNight) Make()
+    {
+        var clock = new GameClock();
+        var calendar = new Calendar(clock, secondsPerDay: 24f); // 1 second = 1 in-game hour
+        return (clock, new DayNight(calendar, DayNightSettings.Default));
+    }
+
+    [Fact]
+    public void Daylight_ZeroAtMidnight_OneAtNoon()
+    {
+        var (clock, dayNight) = Make();
+
+        Assert.Equal(0f, dayNight.Daylight, 3); // 00:00
+
+        clock.Advance(12f); // 12:00
+        Assert.Equal(1f, dayNight.Daylight, 3);
+    }
+
+    [Fact]
+    public void Daylight_RisesFromDawnToNoon()
+    {
+        var (clock, dayNight) = Make();
+
+        clock.Advance(6f); // 06:00
+        var dawn = dayNight.Daylight;
+        clock.Advance(3f); // 09:00
+        var mid = dayNight.Daylight;
+        clock.Advance(3f); // 12:00
+        var noon = dayNight.Daylight;
+
+        Assert.True(dawn < mid && mid < noon, "daylight should rise from dawn to noon");
+    }
+
+    [Fact]
+    public void SunShadow_ZeroAtNight_PointsWestInMorning_EastInAfternoon_ShortAtNoon()
+    {
+        var (clock, dayNight) = Make(); // 1s = 1 in-game hour
+
+        Assert.Equal(Vector2.Zero, dayNight.SunShadow(8f)); // 00:00 — night, no sun
+
+        clock.Advance(7f); // 07:00 — low morning sun in the east
+        var morning = dayNight.SunShadow(8f);
+        Assert.True(morning.X < 0f, "morning shadow points west");
+        Assert.True(morning.Length() > 2f, "low sun casts a long shadow");
+
+        clock.Advance(5f); // 12:00 — sun overhead
+        Assert.True(dayNight.SunShadow(8f).Length() < 1f, "noon sun casts almost no shadow");
+
+        clock.Advance(5f); // 17:00 — afternoon sun in the west
+        Assert.True(dayNight.SunShadow(8f).X > 0f, "afternoon shadow points east");
+    }
+
+    [Fact]
+    public void Ambient_DarkerAtNightThanAtNoon()
+    {
+        var (clock, dayNight) = Make();
+
+        var night = dayNight.Ambient; // 00:00
+        clock.Advance(12f); // 12:00
+        var noon = dayNight.Ambient;
+
+        Assert.True(night.R < noon.R && night.G < noon.G && night.B < noon.B);
+        Assert.Equal(255, noon.R); // day color is white at noon
+    }
+}

tests/MrGameEng.Graphics.Tests/LightmapBuilderTests.cs

@@ -0,0 +1,93 @@
+using Microsoft.Xna.Framework;
+using MrGameEng.Lighting;
+using Xunit;
+
+namespace MrGameEng.Lighting.Tests;
+
+public class LightmapBuilderTests
+{
+    private static float[] Build(
+        int width,
+        int height,
+        float ambient,
+        bool[] occluders,
+        params LightSample[] lights
+    )
+    {
+        var light = new float[width * height];
+        LightmapBuilder.Build(light, width, height, ambient, occluders, lights);
+        return light;
+    }
+
+    [Fact]
+    public void Ambient_WithoutOccluders_IsUniform()
+    {
+        var light = Build(4, 4, 0.6f, new bool[16]);
+        Assert.All(light, v => Assert.Equal(0.6f, v, 5));
+    }
+
+    [Fact]
+    public void OccluderCell_IsDarkerThanOpenCell()
+    {
+        var occ = new bool[9];
+        occ[4] = true; // centre cell shaded
+        var light = Build(3, 3, 0.8f, occ);
+        Assert.True(light[4] < light[0]);
+        Assert.Equal(0.8f * LightmapBuilder.OccluderShade, light[4], 5);
+    }
+
+    [Fact]
+    public void PointLight_IsBrighterNearSourceAndFadesToRadius()
+    {
+        var light = Build(7, 1, 0f, new bool[7], new LightSample(0, 0, 6f, 1f));
+        Assert.True(light[0] > light[2] && light[2] > light[5]);
+        Assert.InRange(light[6], 0f, 0.01f); // на радиусе свет угасает
+    }
+
+    [Fact]
+    public void Occluder_CastsShadowBehindIt()
+    {
+        var occ = new bool[7];
+        occ[3] = true; // препятствие между источником (0) и дальними клетками
+        var light = Build(7, 1, 0f, occ, new LightSample(0, 0, 10f, 1f));
+
+        Assert.True(light[1] > 0f); // перед препятствием — освещено
+        Assert.Equal(0f, light[5], 5); // за препятствием — тень
+    }
+
+    [Fact]
+    public void SunShadow_DarkensCellsInTheShadowDirection_FadingFromTheCaster()
+    {
+        var occ = new bool[7];
+        occ[3] = true; // occluder in the middle
+        var light = new float[7];
+        LightmapBuilder.Build(
+            light,
+            7,
+            1,
+            1f,
+            occ,
+            [],
+            sunShadow: new Vector2(3f, 0f),
+            sunShadowStrength: 0.6f
+        );
+
+        Assert.Equal(1f, light[2], 5); // toward the sun (opposite the shadow) — unshadowed
+        Assert.Equal(LightmapBuilder.OccluderShade, light[3], 5); // occluder cell stays self-shaded
+        Assert.True(light[4] < 1f); // in shadow
+        Assert.True(light[4] < light[6]); // darker near the caster, fading along the shadow
+    }
+
+    [Fact]
+    public void Values_StayWithinUnitRange()
+    {
+        var light = Build(
+            5,
+            5,
+            0.5f,
+            new bool[25],
+            new LightSample(2, 2, 4f, 2f) // яркий свет — проверяем клампинг
+        );
+        Assert.All(light, v => Assert.InRange(v, 0f, 1f));
+    }
+}

tests/MrGameEng.Host.Tests/MrGameEng.Host.Tests.csproj

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <OutputType>Exe</OutputType>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" />
+    <PackageReference Include="xunit.v3" />
+    <PackageReference Include="xunit.runner.visualstudio" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\MrGameEng.Host\MrGameEng.Host.csproj" />
+  </ItemGroup>
+</Project>

tests/MrGameEng.Net.Tests/HeartbeatTests.cs

@@ -0,0 +1,98 @@
+using System.Net;
+using System.Net.Sockets;
+using System.Text;
+using MrGameEng.Net;
+using Xunit;
+
+namespace MrGameEng.Net.Tests;
+
+public class HeartbeatTests
+{
+    [Fact]
+    public async Task HealthyClient_SurvivesPastIdleTimeout()
+    {
+        var port = FreePort();
+        using var server = new WebSocketServer(
+            port,
+            heartbeatInterval: TimeSpan.FromMilliseconds(100),
+            idleTimeout: TimeSpan.FromMilliseconds(400)
+        );
+        server.Start();
+
+        using var client = await WebSocketClient.ConnectAsync(
+            new Uri($"ws://localhost:{port}/"),
+            new CancellationTokenSource(TimeSpan.FromSeconds(10)).Token
+        );
+        var connection = await WaitFor(
+            () => server.TryAcceptConnection(out var c) ? c : null,
+            "server accept"
+        );
+
+        // Дольше idleTimeout: живой клиент авто-отвечает pong на server-ping и остаётся открыт.
+        await Task.Delay(900, TestContext.Current.CancellationToken);
+
+        Assert.True(connection.IsOpen);
+        Assert.True(client.IsOpen);
+    }
+
+    [Fact]
+    public async Task SilentPeer_IsDroppedAfterIdleTimeout()
+    {
+        var port = FreePort();
+        using var server = new WebSocketServer(
+            port,
+            heartbeatInterval: TimeSpan.FromMilliseconds(100),
+            idleTimeout: TimeSpan.FromMilliseconds(400)
+        );
+        server.Start();
+
+        // Сырой peer: проходит рукопожатие, но дальше молчит и не отвечает на ping.
+        using var tcp = new TcpClient();
+        await tcp.ConnectAsync(IPAddress.Loopback, port, TestContext.Current.CancellationToken);
+        var request =
+            "GET / HTTP/1.1\r\n"
+            + "Host: localhost\r\n"
+            + "Upgrade: websocket\r\n"
+            + "Connection: Upgrade\r\n"
+            + "Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==\r\n"
+            + "Sec-WebSocket-Version: 13\r\n"
+            + "\r\n";
+        var bytes = Encoding.ASCII.GetBytes(request);
+        await tcp.GetStream().WriteAsync(bytes, TestContext.Current.CancellationToken);
+
+        var connection = await WaitFor(
+            () => server.TryAcceptConnection(out var c) ? c : null,
+            "server accept"
+        );
+        Assert.True(connection.IsOpen);
+
+        // Peer не отвечает pong'ом → активность не обновляется → сервер закрывает по простою.
+        await WaitFor(() => connection.IsOpen ? null : "closed", "idle drop");
+        Assert.False(connection.IsOpen);
+    }
+
+    private static async Task<T> WaitFor<T>(Func<T?> poll, string what)
+        where T : class
+    {
+        for (var i = 0; i < 200; i++)
+        {
+            if (poll() is { } result)
+            {
+                return result;
+            }
+
+            await Task.Delay(25);
+        }
+
+        throw new TimeoutException($"Timed out waiting for {what}.");
+    }
+
+    private static int FreePort()
+    {
+        var listener = new TcpListener(IPAddress.Loopback, 0);
+        listener.Start();
+        var port = ((IPEndPoint)listener.LocalEndpoint).Port;
+        listener.Stop();
+        return port;
+    }
+}

tests/MrGameEng.Net.Tests/MrGameEng.Net.Tests.csproj

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <OutputType>Exe</OutputType>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" />
+    <PackageReference Include="xunit.v3" />
+    <PackageReference Include="xunit.runner.visualstudio" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\MrGameEng.Net\MrGameEng.Net.csproj" />
+  </ItemGroup>
+</Project>

tests/MrGameEng.Net.Tests/ReplicationTests.cs

@@ -0,0 +1,275 @@
+using System.Collections.Concurrent;
+using Friflo.Engine.ECS;
+using MrGameEng.Net;
+using Xunit;
+
+namespace MrGameEng.Net.Tests;
+
+public class ReplicationTests
+{
+    private struct TestPosition : IComponent
+    {
+        public float X;
+        public float Y;
+    }
+
+    private struct TestHealth : IComponent
+    {
+        public int Value;
+    }
+
+    private sealed class FakeConnection : INetConnection
+    {
+        public int Id { get; init; }
+        public bool IsOpen { get; set; } = true;
+        public readonly ConcurrentQueue<byte[]> Sent = new();
+
+        public void Send(ReadOnlySpan<byte> message) => Sent.Enqueue(message.ToArray());
+
+        public bool TryReceive(out byte[] message) => Sent.TryDequeue(out message!);
+
+        public void Close() => IsOpen = false;
+    }
+
+    private static ReplicationSchema MakeSchema() =>
+        new ReplicationSchema().Register<TestPosition>().Register<TestHealth>();
+
+    [Fact]
+    public void FirstSnapshot_SpawnsEntities_OnTheClient()
+    {
+        var serverStore = new EntityStore();
+        var clientStore = new EntityStore();
+        var server = new ReplicationServer(MakeSchema(), serverStore);
+        var client = new ReplicationClient(MakeSchema(), clientStore);
+        var connection = new FakeConnection();
+
+        serverStore.CreateEntity(
+            new NetId { Value = server.NextNetId() },
+            new TestPosition { X = 10f, Y = 20f },
+            new TestHealth { Value = 7 }
+        );
+        serverStore.CreateEntity(
+            new NetId { Value = server.NextNetId() },
+            new TestPosition { X = -3f, Y = 4f }
+        );
+
+        server.Send([connection]);
+        client.Pump(connection);
+
+        Assert.Equal(2, client.EntityCount);
+        var first = FindByNetId(clientStore, 1);
+        Assert.Equal(10f, first.GetComponent<TestPosition>().X);
+        Assert.Equal(7, first.GetComponent<TestHealth>().Value);
+        var second = FindByNetId(clientStore, 2);
+        Assert.False(second.HasComponent<TestHealth>());
+    }
+
+    [Fact]
+    public void UnchangedWorld_SendsNothing()
+    {
+        var serverStore = new EntityStore();
+        var server = new ReplicationServer(MakeSchema(), serverStore);
+        var connection = new FakeConnection();
+        serverStore.CreateEntity(
+            new NetId { Value = server.NextNetId() },
+            new TestPosition { X = 1f, Y = 1f }
+        );
+
+        server.Send([connection]);
+        Assert.Single(connection.Sent);
+
+        server.Send([connection]);
+        Assert.Single(connection.Sent); // дельта пустая — второго сообщения нет
+    }
+
+    [Fact]
+    public void ChangedComponent_IsTheOnlyThingResent()
+    {
+        var serverStore = new EntityStore();
+        var clientStore = new EntityStore();
+        var server = new ReplicationServer(MakeSchema(), serverStore);
+        var client = new ReplicationClient(MakeSchema(), clientStore);
+        var connection = new FakeConnection();
+
+        var entity = serverStore.CreateEntity(
+            new NetId { Value = server.NextNetId() },
+            new TestPosition { X = 1f, Y = 1f },
+            new TestHealth { Value = 100 }
+        );
+        server.Send([connection]);
+        client.Pump(connection);
+
+        entity.AddComponent(new TestPosition { X = 5f, Y = 6f }); // здоровье не трогаем
+        server.Send([connection]);
+
+        Assert.True(connection.Sent.TryDequeue(out var delta));
+        // Запись: type(1) + version(1) + count(4) + netId(4) + op(1) + mask(4) + TestPosition(8) — без TestHealth.
+        Assert.Equal(23, delta!.Length);
+
+        client.Apply(delta);
+        var replicated = FindByNetId(clientStore, 1);
+        Assert.Equal(5f, replicated.GetComponent<TestPosition>().X);
+        Assert.Equal(100, replicated.GetComponent<TestHealth>().Value);
+    }
+
+    [Fact]
+    public void DeletedEntity_DespawnsOnTheClient()
+    {
+        var serverStore = new EntityStore();
+        var clientStore = new EntityStore();
+        var server = new ReplicationServer(MakeSchema(), serverStore);
+        var client = new ReplicationClient(MakeSchema(), clientStore);
+        var connection = new FakeConnection();
+
+        var entity = serverStore.CreateEntity(
+            new NetId { Value = server.NextNetId() },
+            new TestPosition { X = 1f, Y = 1f }
+        );
+        server.Send([connection]);
+        client.Pump(connection);
+        Assert.Equal(1, client.EntityCount);
+
+        entity.DeleteEntity();
+        server.Send([connection]);
+        client.Pump(connection);
+
+        Assert.Equal(0, client.EntityCount);
+    }
+
+    [Fact]
+    public void LateJoiner_GetsFullState()
+    {
+        var serverStore = new EntityStore();
+        var server = new ReplicationServer(MakeSchema(), serverStore);
+        var early = new FakeConnection { Id = 1 };
+        var late = new FakeConnection { Id = 2 };
+
+        serverStore.CreateEntity(
+            new NetId { Value = server.NextNetId() },
+            new TestPosition { X = 9f, Y = 9f }
+        );
+        server.Send([early]);
+        server.Send([early, late]); // мир не менялся: early — тишина, late — полный стейт
+
+        Assert.Single(early.Sent);
+        Assert.Single(late.Sent);
+
+        var clientStore = new EntityStore();
+        var client = new ReplicationClient(MakeSchema(), clientStore);
+        client.Pump(late);
+        Assert.Equal(1, client.EntityCount);
+        Assert.Equal(9f, FindByNetId(clientStore, 1).GetComponent<TestPosition>().X);
+    }
+
+    [Fact]
+    public void EntitySpawned_FiresOncePerEntity()
+    {
+        var serverStore = new EntityStore();
+        var clientStore = new EntityStore();
+        var server = new ReplicationServer(MakeSchema(), serverStore);
+        var client = new ReplicationClient(MakeSchema(), clientStore);
+        var connection = new FakeConnection();
+        var spawns = 0;
+        client.EntitySpawned += _ => spawns++;
+
+        var entity = serverStore.CreateEntity(
+            new NetId { Value = server.NextNetId() },
+            new TestPosition { X = 1f, Y = 1f }
+        );
+        server.Send([connection]);
+        client.Pump(connection);
+        entity.AddComponent(new TestPosition { X = 2f, Y = 2f });
+        server.Send([connection]);
+        client.Pump(connection);
+
+        Assert.Equal(1, spawns);
+    }
+
+    [Fact]
+    public void Clear_DeletesEveryReplicatedEntity()
+    {
+        var serverStore = new EntityStore();
+        var clientStore = new EntityStore();
+        var server = new ReplicationServer(MakeSchema(), serverStore);
+        var client = new ReplicationClient(MakeSchema(), clientStore);
+        var connection = new FakeConnection();
+        serverStore.CreateEntity(
+            new NetId { Value = server.NextNetId() },
+            new TestPosition { X = 1f, Y = 2f }
+        );
+        serverStore.CreateEntity(
+            new NetId { Value = server.NextNetId() },
+            new TestPosition { X = 3f, Y = 4f }
+        );
+        server.Send([connection]);
+        client.Pump(connection);
+        Assert.Equal(2, client.EntityCount);
+
+        client.Clear();
+
+        Assert.Equal(0, client.EntityCount);
+        foreach (var entity in clientStore.Entities)
+        {
+            Assert.False(entity.HasComponent<NetId>());
+        }
+    }
+
+    [Fact]
+    public void MismatchedProtocolVersion_IsDropped()
+    {
+        var serverStore = new EntityStore();
+        var clientStore = new EntityStore();
+        var server = new ReplicationServer(MakeSchema(), serverStore);
+        var client = new ReplicationClient(MakeSchema(), clientStore);
+        var connection = new FakeConnection();
+        serverStore.CreateEntity(
+            new NetId { Value = server.NextNetId() },
+            new TestPosition { X = 1f, Y = 2f }
+        );
+        server.Send([connection]);
+        Assert.True(connection.Sent.TryDequeue(out var snapshot));
+
+        // Портим байт версии (индекс 1: type=0, version=1) — клиент обязан отбросить снапшот целиком.
+        snapshot![1] = 0xFF;
+        client.Apply(snapshot);
+
+        Assert.Equal(0, client.EntityCount);
+    }
+
+    [Fact]
+    public void TruncatedSnapshot_IsIgnoredWithoutThrowing()
+    {
+        var serverStore = new EntityStore();
+        var clientStore = new EntityStore();
+        var server = new ReplicationServer(MakeSchema(), serverStore);
+        var client = new ReplicationClient(MakeSchema(), clientStore);
+        var connection = new FakeConnection();
+        serverStore.CreateEntity(
+            new NetId { Value = server.NextNetId() },
+            new TestPosition { X = 5f, Y = 6f },
+            new TestHealth { Value = 9 }
+        );
+        server.Send([connection]);
+        Assert.True(connection.Sent.TryDequeue(out var snapshot));
+
+        // Режем хвост: заголовок и счётчик целы, но данные компонентов оборваны.
+        var truncated = snapshot!.AsSpan(0, snapshot.Length - 6).ToArray();
+        client.Apply(truncated); // не должно бросить
+
+        // Записи могли частично примениться, но клиент остался живым и консистентным.
+        Assert.True(client.EntityCount <= 1);
+    }
+
+    private static Entity FindByNetId(EntityStore store, int netId)
+    {
+        foreach (var entity in store.Entities)
+        {
+            if (entity.HasComponent<NetId>() && entity.GetComponent<NetId>().Value == netId)
+            {
+                return entity;
+            }
+        }
+
+        throw new InvalidOperationException($"Entity with NetId {netId} not found.");
+    }
+}

tests/MrGameEng.Net.Tests/WebSocketLoopbackTests.cs

@@ -0,0 +1,93 @@
+using System.Net;
+using System.Net.Sockets;
+using MrGameEng.Net;
+using Xunit;
+
+namespace MrGameEng.Net.Tests;
+
+public class WebSocketLoopbackTests
+{
+    [Fact]
+    public async Task ClientAndServer_ExchangeBinaryMessages_OverLoopback()
+    {
+        var port = FreePort();
+        using var server = new WebSocketServer(port);
+        server.Start();
+
+        using var client = await WebSocketClient.ConnectAsync(
+            new Uri($"ws://localhost:{port}/"),
+            new CancellationTokenSource(TimeSpan.FromSeconds(10)).Token
+        );
+
+        var connection = await WaitFor(
+            () => server.TryAcceptConnection(out var c) ? c : null,
+            "server accept"
+        );
+
+        // Сервер → клиент.
+        connection.Send([1, 2, 3, 250]);
+        var received = await WaitFor(
+            () => client.TryReceive(out var m) ? m : null,
+            "client receive"
+        );
+        Assert.Equal(new byte[] { 1, 2, 3, 250 }, received);
+
+        // Клиент → сервер (ClientWebSocket маскирует кадры — сервер обязан размаскировать).
+        client.Send([9, 8, 7]);
+        var echoed = await WaitFor(
+            () => connection.TryReceive(out var m) ? m : null,
+            "server receive"
+        );
+        Assert.Equal(new byte[] { 9, 8, 7 }, echoed);
+
+        Assert.True(connection.IsOpen);
+        Assert.True(client.IsOpen);
+    }
+
+    [Fact]
+    public async Task ClosingTheClient_ClosesTheServerConnection()
+    {
+        var port = FreePort();
+        using var server = new WebSocketServer(port);
+        server.Start();
+
+        var client = await WebSocketClient.ConnectAsync(
+            new Uri($"ws://localhost:{port}/"),
+            new CancellationTokenSource(TimeSpan.FromSeconds(10)).Token
+        );
+        var connection = await WaitFor(
+            () => server.TryAcceptConnection(out var c) ? c : null,
+            "server accept"
+        );
+
+        client.Close();
+
+        await WaitFor(() => connection.IsOpen ? null : "closed", "server-side close");
+        Assert.False(connection.IsOpen);
+    }
+
+    private static async Task<T> WaitFor<T>(Func<T?> poll, string what)
+        where T : class
+    {
+        for (var i = 0; i < 200; i++)
+        {
+            if (poll() is { } result)
+            {
+                return result;
+            }
+
+            await Task.Delay(25);
+        }
+
+        throw new TimeoutException($"Timed out waiting for {what}.");
+    }
+
+    private static int FreePort()
+    {
+        var listener = new TcpListener(IPAddress.Loopback, 0);
+        listener.Start();
+        var port = ((IPEndPoint)listener.LocalEndpoint).Port;
+        listener.Stop();
+        return port;
+    }
+}

tests/MrGameEng.Net.Tests/WebSocketProtocolTests.cs

@@ -0,0 +1,88 @@
+using MrGameEng.Net;
+using Xunit;
+
+namespace MrGameEng.Net.Tests;
+
+public class WebSocketProtocolTests
+{
+    [Fact]
+    public void AcceptKey_MatchesRfc6455Example()
+    {
+        // Пример рукопожатия прямо из RFC 6455, раздел 1.3.
+        Assert.Equal(
+            "s3pPLMBiTxaQ9kYGzzhZRbK+xOo=",
+            WebSocketProtocol.AcceptKey("dGhlIHNhbXBsZSBub25jZQ==")
+        );
+    }
+
+    [Theory]
+    [InlineData(0)]
+    [InlineData(125)]
+    [InlineData(126)]
+    [InlineData(70_000)]
+    public void Frame_Roundtrips_Unmasked(int payloadLength)
+    {
+        var payload = MakePayload(payloadLength);
+        var frame = WebSocketProtocol.EncodeFrame(payload, WebSocketOpcode.Binary);
+
+        using var stream = new MemoryStream(frame);
+        Assert.True(
+            WebSocketProtocol.TryReadFrame(stream, out var opcode, out var fin, out var decoded)
+        );
+        Assert.Equal(WebSocketOpcode.Binary, opcode);
+        Assert.True(fin);
+        Assert.Equal(payload, decoded);
+    }
+
+    [Fact]
+    public void Frame_Roundtrips_Masked()
+    {
+        var payload = MakePayload(1000);
+        var frame = WebSocketProtocol.EncodeFrame(
+            payload,
+            WebSocketOpcode.Binary,
+            maskKey: [0x12, 0x34, 0x56, 0x78]
+        );
+
+        using var stream = new MemoryStream(frame);
+        Assert.True(WebSocketProtocol.TryReadFrame(stream, out _, out _, out var decoded));
+        Assert.Equal(payload, decoded);
+    }
+
+    [Fact]
+    public void TryReadHandshakeKey_ExtractsHeader()
+    {
+        var request =
+            "GET /chat HTTP/1.1\r\n"
+            + "Host: localhost\r\n"
+            + "Upgrade: websocket\r\n"
+            + "Connection: Upgrade\r\n"
+            + "Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==\r\n"
+            + "Sec-WebSocket-Version: 13\r\n"
+            + "\r\n";
+        using var stream = new MemoryStream(System.Text.Encoding.ASCII.GetBytes(request));
+
+        Assert.True(WebSocketProtocol.TryReadHandshakeKey(stream, out var key));
+        Assert.Equal("dGhlIHNhbXBsZSBub25jZQ==", key);
+    }
+
+    [Fact]
+    public void TryReadFrame_TruncatedStream_ReturnsFalse()
+    {
+        var frame = WebSocketProtocol.EncodeFrame(MakePayload(100), WebSocketOpcode.Binary);
+        using var stream = new MemoryStream(frame, 0, frame.Length - 10);
+
+        Assert.False(WebSocketProtocol.TryReadFrame(stream, out _, out _, out _));
+    }
+
+    private static byte[] MakePayload(int length)
+    {
+        var payload = new byte[length];
+        for (var i = 0; i < length; i++)
+        {
+            payload[i] = (byte)(i * 31);
+        }
+
+        return payload;
+    }
+}

tests/MrGameEng.Simulation.Tests/AI/SuitabilityTests.cs

@@ -0,0 +1,92 @@
+using MrGameEng.AI;
+using Xunit;
+
+namespace MrGameEng.AI.Tests;
+
+public class SuitabilityTests
+{
+    [Fact]
+    public void Gaussian_PeaksAtOptimum()
+    {
+        Assert.Equal(1f, Suitability.Gaussian(18f, optimum: 18f, tolerance: 5f), 5);
+    }
+
+    [Fact]
+    public void Gaussian_IsSymmetricAroundOptimum()
+    {
+        var below = Suitability.Gaussian(13f, optimum: 18f, tolerance: 5f);
+        var above = Suitability.Gaussian(23f, optimum: 18f, tolerance: 5f);
+        Assert.Equal(below, above, 5);
+    }
+
+    [Fact]
+    public void Gaussian_AtOneToleranceAway_IsAboutPoint607()
+    {
+        Assert.Equal(MathF.Exp(-0.5f), Suitability.Gaussian(23f, 18f, 5f), 5);
+    }
+
+    [Fact]
+    public void Gaussian_FallsOffWithDistance()
+    {
+        var near = Suitability.Gaussian(20f, 18f, 5f);
+        var far = Suitability.Gaussian(30f, 18f, 5f);
+        Assert.True(far < near && far > 0f);
+    }
+
+    [Fact]
+    public void Gaussian_StaysWithinUnitRange()
+    {
+        for (var v = -50f; v <= 50f; v += 1f)
+        {
+            Assert.InRange(Suitability.Gaussian(v, 0f, 7f), 0f, 1f);
+        }
+    }
+
+    [Fact]
+    public void Gaussian_NonPositiveTolerance_IsExactMatch()
+    {
+        Assert.Equal(1f, Suitability.Gaussian(5f, 5f, 0f));
+        Assert.Equal(0f, Suitability.Gaussian(6f, 5f, 0f));
+    }
+
+    [Fact]
+    public void Trapezoid_IsFlatAcrossThePlateau()
+    {
+        Assert.Equal(1f, Suitability.Trapezoid(10f, 0f, 10f, 42f, 58f), 5);
+        Assert.Equal(1f, Suitability.Trapezoid(25f, 0f, 10f, 42f, 58f), 5);
+        Assert.Equal(1f, Suitability.Trapezoid(42f, 0f, 10f, 42f, 58f), 5);
+    }
+
+    [Fact]
+    public void Trapezoid_RampsLinearlyOnEachShoulder()
+    {
+        Assert.Equal(0.5f, Suitability.Trapezoid(5f, 0f, 10f, 42f, 58f), 5); // halfway up the cold ramp
+        Assert.Equal(0.5f, Suitability.Trapezoid(50f, 0f, 10f, 42f, 58f), 5); // halfway down the heat ramp
+    }
+
+    [Fact]
+    public void Trapezoid_IsZeroAtAndBeyondTheHardLimits()
+    {
+        Assert.Equal(0f, Suitability.Trapezoid(0f, 0f, 10f, 42f, 58f));
+        Assert.Equal(0f, Suitability.Trapezoid(-5f, 0f, 10f, 42f, 58f));
+        Assert.Equal(0f, Suitability.Trapezoid(58f, 0f, 10f, 42f, 58f));
+        Assert.Equal(0f, Suitability.Trapezoid(70f, 0f, 10f, 42f, 58f));
+    }
+
+    [Fact]
+    public void Trapezoid_DegenerateShoulder_IsAHardStep()
+    {
+        // optimalLow == min: full suitability immediately above the lower limit, zero at/below it.
+        Assert.Equal(1f, Suitability.Trapezoid(5f, 0f, 0f, 10f, 20f));
+        Assert.Equal(0f, Suitability.Trapezoid(0f, 0f, 0f, 10f, 20f));
+    }
+
+    [Fact]
+    public void Trapezoid_StaysWithinUnitRange()
+    {
+        for (var v = -50f; v <= 80f; v += 1f)
+        {
+            Assert.InRange(Suitability.Trapezoid(v, 0f, 10f, 42f, 58f), 0f, 1f);
+        }
+    }
+}