# 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.

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
docs/          концепт, симуляция, 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
```

## Texture atlases

Source images live in `textures/` (committed); the game only loads packed atlases from
`src/LittleSim/Assets/Atlases` (also committed — the asset generator emits
`GameAssets.Atlases.*` handles for them). After changing `textures/`, rebuild with:

```
dotnet run --project engine/tools/MrGameEng.AtlasTool -c Release -- textures src/LittleSim/Assets/Atlases --group-depth 2
```

Rebuilds are incremental (unchanged groups are skipped). Region keys are paths relative
to `textures/` without extension: `atlas.GetRegion("things/plant/treeoak/TreeOakA")`.

## 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.
- Every new mechanic gets a dev-console command for testing (`regen`, `timescale`, …).