# LittleSim

A god-game: minimal graphics, deep simulation. Built on the **mrgameeng** engine
(MonoGame + Friflo ECS), vendored as the git submodule `engine/` so the game and the
engine are developed side by side in one editor window.

This game is also the **engine's showcase**: mrgameeng has no sample project, so every
new engine feature gets demonstrated here (a scene, a console command, or a system
using it) as part of landing the feature.

Game design docs live in `docs/` and are written in **Russian**. Engine rules live in
`engine/CLAUDE.md` — read it before touching engine code; both rule sets apply here.

## Layout

```
engine/        mrgameeng git submodule (own repo, own CLAUDE.md)
src/LittleSim  the game (net8.0); references engine projects directly
Mods/Core      the game's own content as a mod: About, Defs, Languages, Textures
Cache/         runtime-built atlases (gitignored)
docs/          концепт, симуляция, моды, roadmap (Russian)
LittleSim.sln  game + engine sources + engine tests — one window for everything
```

## Commands

```
git submodule update --init             # after fresh clone
dotnet build LittleSim.sln
dotnet run --project src/LittleSim -c Release   # measure perf in Release only
dotnet test LittleSim.sln                        # runs the engine test suites
```

## Content and mods

All game content is data in mods (`MrGameEng.Mods`): the game itself ships as the
`Core` mod. `Mods/Core/Defs` holds JSON defs (terrain, plants, pawns — see
`docs/mods.md`), `Mods/Core/Languages/{ru,en}` holds UI strings (default language is
`ru`), `Mods/Core/Textures` holds source images. New mechanics get defs + localization
keys, not hardcoded arrays; UI strings go through `LanguageManager`, never inline.

Atlases are built **at game start** from the merged texture tree of all active mods
into `Cache/Atlases` (incremental: unchanged groups are skipped, a clean first run
takes ~20 s). Region keys are paths relative to `Textures/` without extension:
`atlases.GetRegion(device, "things/plant/treeoak/TreeOakA")`. Console commands:
`mods`, `lang [code]`, `defs [type]`, `atlas [name]`.

## Submodule workflow

Engine changes are committed **inside `engine/` first** (engine repo, its commit style),
pushed to the engine remote, then the submodule pointer bump is committed here.
Never commit a pointer to an unpushed engine commit.

## Game rules

- Simulation first: depth of behavior over visuals. Graphics stay primitive
  (tinted quads are fine); complexity budget goes to simulation systems.
- Determinism: the whole world derives from one integer seed. Systems that need
  randomness own a seeded `Random`; never use `Random.Shared` inside simulation.
- Simulation/presentation split: simulation systems mutate components only;
  rendering reads them. No draw calls or UI from simulation systems.
- ECS-first per the engine: plain `struct : IComponent` data, logic in systems.
- Content as data: numbers, textures and balance live in `Mods/Core/Defs`, user-facing
  strings in `Mods/Core/Languages` — code only defines systems and def classes.
- Every new mechanic gets a dev-console command for testing (`regen`, `timescale`, …).
- Formatting: all C# code is formatted with **CSharpier** (`editor.defaultFormatter`
  is `csharpier.csharpier-vscode`, format-on-save is on). Match CSharpier's output —
  run `csharpier format .` (or let format-on-save handle it) before committing; never
  hand-format against it.
