# mrgameeng

2D game engine built on MonoGame 3.8.4 (DesktopGL), .NET 8, C#.
ECS-first: Friflo.Engine.ECS 3.6 is tightly integrated into the core — all gameplay
state lives in components, all logic in systems.

Design docs and developer documentation live in `docs/` and are written in **Russian**.
Keep them up to date when architecture or conventions change.

## Solution layout

```
src/      MrGameEng.* engine libraries (one per functional area)
samples/  MrGameEng.Sample — demo game showcasing every engine feature
tests/    xUnit test projects, one per engine library
docs/     architecture, conventions, roadmap (Russian)
```

Engine modules: `Core` (game loop, ECS world, scenes, time), `Graphics` (custom batched
renderer, camera, sprites), `Input`, `Audio`, `Assets` (runtime loading, no content
pipeline), `Assets.Generator` (Roslyn source generator for typed asset handles),
`UI` (Myra integration: `scene.UseUI()` after `UseRenderer2D()`).
Dependency rule: every module may depend only on `Core`; `Core` depends only on
MonoGame and Friflo.Engine.ECS. `Assets.Generator` is a netstandard2.0 analyzer.
Documented exception: Myra renders with its own SpriteBatch internally.

## Commands

```
dotnet build MrGameEng.sln
dotnet test MrGameEng.sln
dotnet run --project samples/MrGameEng.Sample
```

## Architecture rules

- ECS-first: components are plain data (`struct` implementing `IComponent`),
  behavior goes into Friflo systems (`QuerySystem`), wired through `SystemRoot`.
  No `Update()` methods on game objects, no inheritance-based entities.
- Hot paths (per-frame systems) must be allocation-free below the renderer's parallel
  threshold; above it Parallel.For scheduler overhead is the accepted trade.
  A Friflo chunk holds a whole archetype — parallelize by slicing chunks into segments,
  never by chunk alone. Measure in Release only, using the Renderer2D phase timings.
- Rendering: custom batcher in `Graphics` (vertex buffers, layer→depth→texture sort,
  atlas support); `SpriteBatch` is not used in engine code. Draw systems write vertices
  directly from Friflo chunk iteration. Orthographic camera (one active per scene),
  registered render layers (World or Screen space, optional Y-sort), AABB culling
  against the camera rect before vertices are written.
- No MGCB content pipeline. Assets are raw files under `Assets/`, loaded at runtime
  (textures via `Texture2D.FromFile`, fonts via FontStashSharp, ogg via NVorbis,
  shaders precompiled by `dotnet-mgfxc` at build time). Game code references assets
  only through generated typed handles (`AssetRef<T>`), never string paths.
- New engine functionality goes into the matching module, or a new
  `MrGameEng.<Area>` library if it is a distinct area — never into `Core` by default.
- Every public engine feature must be demonstrated in `MrGameEng.Sample`
  and covered by tests where logic is testable without a GPU.

## Code conventions

- Nullable reference types enabled, warnings as errors, file-scoped namespaces.
- Public engine API requires XML doc comments (English).
- Tests: xUnit, named `Method_Scenario_Expectation`.