# Color Book — Architecture Guide

A toddler-targeted (ages 2–6) coloring book game built on the same **Strict Modular Monolith** pattern as the Bus Game. Powered by **VContainer** for DI, **UniTask** for async, **Addressables** for shipped content, and a **hybrid Sprites + Canvas** render strategy.

This document is the canonical reference for the Color Book game's structure. The Bus Game's [Darkmatter Architecture Guide](../Assets/Darkmatter_Architecture_Guide.md) is the parent contract; this doc only adds game-specific structure.

---

## 1. Game Flow

```
App launch
  └─ Boot scene (RootLifetimeScope)
      └─ MainMenu scene
          ├─ Press "Play"   → ColorBook scene
          │     ├─ Drawing catalog (grid of templates)
          │     ├─ Select drawing
          │     ├─ Shape Builder panel  (drag pieces → snap to slots)
          │     ├─ ↓ on assembly complete
          │     ├─ Color panel          (tap color → tap region)
          │     ├─ Undo / Redo any time
          │     ├─ "Capture" → save to Gallery with paper background
          │     └─ "Next"   → auto-save + load next drawing
          └─ Press "Art Book" → ArtBook scene (gallery viewer)
                ├─ Grid of saved artworks
                ├─ View / share / delete
                └─ Save to device camera roll
```

---

## 2. Philosophy

Identical to Bus Game:

- **Vertical slices** — code grouped by Feature, not by type.
- **Strict layering** — dependencies flow downward only.
- **Composition over inheritance** — wired by DI.
- **Code vs Content** — `Code/` for logic, `Contents/` for assets.

Game-specific additions:

- **Toddler-first UX** — large hitboxes, forgiving snap radii, no fail states, no timers.
- **Stateless replay** — every action (paint, snap) is an `ICommand` so undo/redo and auto-save are trivial.
- **Capture-as-truth** — the gallery is a folder of PNGs on disk, not a serialized scene graph. What the child sees is what gets saved.

---

## 3. Dependency Graph

```
App   ──────────┐
                ▼
Features ──► Core ◄── Services
                ▲
                └── Libs
```

### Forbidden actions

- Services cannot reference Features.
- Features cannot reference Service implementations — only Core contracts via DI.
- Features cannot reference other Features — use `IEventBus` signals or Core contracts.
- Core may not contain logic. Interfaces, enums, DTOs, signal records only.
- Core may reference `UniTask` for async contract signatures. Nothing else.

---

## 4. Folder Structure

This section reflects the **actual project on disk today**. Empty folders that have been reserved for upcoming work are marked `(planned)`; everything else has at least one file in it. Aspirational additions for the rest of the game are listed in §4c at the bottom.

### 4a. Actual layout on disk

```
Assets/Darkmatter/
├── Scenes/
│   └── Boot.unity                                          ← only scene wired so far
│
├── Content/                                                ← singular ("Content", not "Contents")
│   └── Gameplay/
│       └── PaperRig/                                       ← (planned — paper rig prefabs)
│
├── Data/
│   ├── Inputs/                                             (Input System .inputactions)
│   └── Settings/
│       ├── Persistance/Resources/                          (ProtectedPlayerPrefs settings)
│       ├── Rendering/                                      (URP renderer + asset)
│       └── Scenes/URP2DSceneTemplate.unity
│
└── Code/
    ├── App/
    │   └── LifetimeScopes/
    │       └── RootLifetimeScope.cs                        ← scope loads serialized IServiceModule list
    │   Darkmatter.App.asmdef
    │
    ├── Core/                                               (asmdef name: `Core`, namespace root `Darkmatter.Core.*`)
    │   ├── Compatibility/
    │   │   └── IsExternalInit.cs                           (C#9 init shim for older runtimes)
    │   ├── Contracts/
    │   │   ├── Paper/                                      ← misplaced empty folder — should be Contracts/Features/Paper/ (delete or move)
    │   │   └── Services/
    │   │       ├── Assets/IAssetProviderService.cs
    │   │       ├── Audio/IAudioService.cs, ISfxPlayer.cs
    │   │       ├── Camera/ICameraService.cs
    │   │       ├── Capture/                                ← (planned — ICaptureService)
    │   │       ├── Inputs/IInputReader.cs
    │   │       └── Scenes/ISceneService.cs
    │   ├── Data/
    │   │   ├── Dynamic/Services/Audio/                     (AudioHandle, AudioRequest)
    │   │   └── Static/Services/Audio/                      (SfxCatalogSO)
    │   └── Enums/
    │       └── Services/
    │           ├── Audio/                                  (AudioChannel, AudioPlayMode, SfxId)
    │           ├── Camera/CameraType.cs                    (MainCamera, UICamera — ArtCamera not added yet)
    │           └── Scenes/GameScene.cs
    │
    ├── Features/                                           ← (planned — empty folder today)
    │
    ├── Libs/
    │   ├── FSM/                                            (IState, State, StateMachine + Docs)
    │   │   Libs.FSM.asmdef
    │   ├── Installers/                                     (IServiceModule — Register(IContainerBuilder))
    │   │   Libs.Installers.asmdef
    │   ├── Observer/                                       (IEventBus, EventBus — note: not named "EventBus")
    │   │   Libs.Observer.asmdef
    │   ├── PlayerPrefs/                                    (ProtectedPlayerPrefs — used in place of a Persistence service)
    │   │   ├── Editor/   Libs.PlayerPrefs.Editor.asmdef
    │   │   └── Runtime/  Libs.PlayerPrefs.asmdef
    │   └── UI/                                             (ToggleButton, ToggleButtonGroup)
    │       Libs.UI.asmdef
    │
    └── Services/
        ├── Analytics/
        │   ├── Installers/AnalyticsServiceModule.cs
        │   └── Systems/FirebaseAnalyticsSystem.cs
        │   Services.Analytics.asmdef
        ├── Assets/
        │   ├── AddressableAssetProviderService.cs
        │   └── AddressableLoadHandleTracker.cs
        │   Services.Assets.asmdef
        ├── Audio/
        │   ├── AudioService.cs
        │   └── SfxPlayer.cs
        │   Services.Audio.asmdef
        ├── Camera/
        │   ├── Installers/CameraServiceModule.cs
        │   └── Service/CameraService.cs
        │   Services.Camera.asmdef
        ├── Inputs/
        │   ├── Generated/GameInputs.cs                     (Input System codegen)
        │   ├── Installers/InputServiceModule.cs
        │   └── Readers/InputReaderSO.cs
        │   Services.Inputs.asmdef
        └── Scenes/
            └── SceneService.cs
            Services.Scenes.asmdef
```

### 4b. Conventions visible in current code

- **Asmdef per Service / Lib / App / Core.** No Feature asmdefs yet (folder is empty).
- **Core sub-tree shape:** `Core/{Compatibility, Contracts, Data, Enums}` — deeply nested by Service rather than by topic. Game-specific Core types (Drawing, Coloring, Paper, Gallery, History, Progression, Signals) will be added under either `Core/Contracts/<Area>/` or new top-level `Core/<Area>/` — pick one convention before adding the first one.
- **Service sub-shape varies** — some are flat (`Services/Audio/*.cs`), some split (`Services/Camera/Installers/`, `Services/Camera/Service/`). The "official" per-feature shape (§4d) hasn't been validated against real code yet.
- **Installer pattern:** `MonoBehaviour, IServiceModule` with `Register(IContainerBuilder builder)`. **Not** `IInstaller.Install(...)` as older sections of this doc imply. New installers must follow `IServiceModule`.
- **No `AppBoot`** entry point exists yet. `RootLifetimeScope` only iterates a serialized `MonoBehaviour[] serviceModules` and calls `Register` on each `IServiceModule`. Boot sequence in §29 is aspirational.
- **No Persistence service.** `Libs/PlayerPrefs` (the `ProtectedPlayerPrefs` library) is in place for small-key state. JSON persistence for gallery sidecars will need a separate service when Gallery lands.
- **Camera service is a registry**, not a fitter. `ICameraService.Register/Get` only — no aspect-fit logic.

### 4c. Planned additions (not on disk yet)

All new game code follows the same nesting pattern as existing Services — `Contracts/Features/<Name>/`, `Data/{Dynamic,Static}/Features/<Name>/`, `Features/<Name>/` — and asmdefs drop the `Darkmatter.` prefix to match `Core`, `Services.Audio`, `Libs.Observer`.

Rough landing order for ColorBook scene to be playable:

| Path | Role |
|---|---|
| `Core/Contracts/Features/Paper/IPaperRig.cs`, `IArtInputBridge.cs` | Paper rig contracts |
| `Core/Contracts/Services/Capture/ICaptureService.cs` | Capture service contract |
| `Core/Contracts/Services/Gallery/IGalleryService.cs` | Gallery service contract |
| `Core/Contracts/Features/Drawing/IDrawingTemplate.cs`, `IDrawingTemplateCatalog.cs` | Drawing template contracts |
| `Core/Contracts/Features/Coloring/IColorPalette.cs` | Palette contract |
| `Core/Contracts/Features/History/ICommand.cs`, `IUndoStack.cs` | Undo/redo contracts |
| `Core/Contracts/Features/Progression/IProgressionService.cs` | Progression contract (despite the name, it's a feature contract since it's game-specific) |
| `Core/Data/Static/Features/Drawing/` (DrawingTemplateSO) | Authored drawing data |
| `Core/Data/Static/Features/Coloring/` (ColorPaletteSO) | Authored palette data |
| `Core/Data/Dynamic/Features/Drawing/ShapePieceDTO.cs`, `ColorRegionDTO.cs` | Runtime drawing structs |
| `Core/Data/Dynamic/Features/Coloring/PaintCommandDTO.cs` | Runtime coloring struct |
| `Core/Data/Dynamic/Features/Gallery/SavedArtworkDTO.cs` | Runtime gallery struct |
| `Core/Data/Dynamic/Features/Signals/` (DrawingSelectedSignal, ShapeAssembledSignal, ColorAppliedSignal, ArtworkCapturedSignal, ArtworkSavedSignal) | Cross-feature signal structs |
| `Core/Enums/Services/Camera/CameraType.cs` | Add `ArtCamera` enum value to existing file |
| `Libs/CommandStack/` (+ `Libs.CommandStack.asmdef`) | Bounded undo/redo |
| `Services/Capture/` (+ `Services.Capture.asmdef`) | `RenderTextureCaptureService` reads `IPaperRig.Surface` |
| `Services/Gallery/` (+ `Services.Gallery.asmdef`) | `FileGalleryService` — PNG + sidecar JSON IO |
| `Features/Paper/` (+ `Features.Paper.asmdef`) | Scene-bound RT rig |
| `Features/{MainMenu,DrawingCatalog,ShapeBuilder,Coloring,History,Capture,Progression,ColorBookFlow,ArtBook}/` (+ asmdefs each) | Game features |
| `App/LifetimeScopes/{MainMenu,ColorBook,ArtBook}LifetimeScope.cs` | Per-scene scopes |
| `App/Boot/AppBoot.cs` | Bootstrap entry point |
| `Assets/Darkmatter/Scenes/{MainMenu,ColorBook,ArtBook}.unity` | Scenes |
| `Content/Gameplay/Drawings/<theme>/<id>/{Template.asset, Pieces/, Regions/, PaperBackground.png}` | Authored drawings (under existing `Content/Gameplay/` root) |
| `Content/Gameplay/Palettes/*.asset` | Color palettes |
| `Content/Audio/{UI,Coloring}/` | SFX banks |

### 4d. Per-feature folder layout (matches existing Services pattern)

Look at `Services/Camera/` (`Installers/` + `Service/`) and `Services/Analytics/` (`Installers/` + `Systems/`) — that's the convention. Features adopt the same shape, adding `UI/` or `Views/` only when there's something to put in them.

```
Features/[Name]/
├── Installers/                IServiceModule — VContainer registration
├── Systems/   (or Service/)   Controllers, repositories, factories (pure C#)
├── UI/                        (only if the feature has Canvas UI)
│   ├── *Presenter.cs          Pure C#, listens to model, drives view
│   └── *View.cs               MonoBehaviour, setters only
├── Views/                     (only if the feature has world-space MonoBehaviours)
└── Features.<Name>.asmdef
```

Rules of thumb pulled from current Services:
- **Use `Service/` (singular)** when the feature has exactly one main implementation class (like `Services/Camera/Service/CameraService.cs`).
- **Use `Systems/` (plural)** when there are multiple pure-C# coordinators (like `Services/Analytics/Systems/`).
- **Skip nesting entirely** when the feature has only 1–2 files at root (like `Services/Audio/AudioService.cs` + `SfxPlayer.cs` flat).
- **`Docs/` is per-folder** in current code — drop a `Docs/` inside any sub-folder that needs notes, don't make a global feature-level Docs.

---

## 5. Namespaces & Asmdef naming

C# namespace pattern is `Darkmatter.<Layer>.<Module>[.<SubArea>]` — the `Darkmatter.` prefix stays on namespaces. Examples already in code:

- `Darkmatter.Core.Contracts.Services.Camera` ([ICameraService.cs](Assets/Darkmatter/Code/Core/Contracts/Services/Camera/ICameraService.cs))
- `Darkmatter.Services.Camera` ([CameraService.cs](Assets/Darkmatter/Code/Services/Camera/Service/CameraService.cs))
- `Darkmatter.Services.Camera.Installers` ([CameraServiceModule.cs](Assets/Darkmatter/Code/Services/Camera/Installers/CameraServiceModule.cs))
- `Darkmatter.Libs.Installers` ([IServiceModule.cs](Assets/Darkmatter/Code/Libs/Installers/IServiceModule.cs))

**Asmdef names drop the `Darkmatter.` prefix.** Existing pattern:

| Namespace | Asmdef |
|---|---|
| `Darkmatter.Core.*` | `Core` |
| `Darkmatter.App` | `Darkmatter.App` (one exception — keep as-is, don't churn) |
| `Darkmatter.Libs.Observer` | `Libs.Observer` |
| `Darkmatter.Libs.FSM` | `Libs.FSM` |
| `Darkmatter.Libs.Installers` | `Libs.Installers` |
| `Darkmatter.Libs.PlayerPrefs` | `Libs.PlayerPrefs` (+ `Libs.PlayerPrefs.Editor`) |
| `Darkmatter.Libs.UI` | `Libs.UI` |
| `Darkmatter.Services.Audio` | `Services.Audio` |
| `Darkmatter.Services.Assets` | `Services.Assets` |
| `Darkmatter.Services.Camera` | `Services.Camera` |
| `Darkmatter.Services.Inputs` | `Services.Inputs` |
| `Darkmatter.Services.Scenes` | `Services.Scenes` |
| `Darkmatter.Services.Analytics` | `Services.Analytics` |

New asmdefs follow the same convention: `Services.Capture`, `Services.Gallery`, `Libs.CommandStack`, `Features.Paper`, `Features.Coloring`, etc.

---

## 6. Scenes & Lifetime Scopes

| Scene | Scope | Status | Contents |
|---|---|---|---|
| `Boot.unity` | `RootLifetimeScope` | ✅ exists | All Services + Libs. Persists forever. |
| `MainMenu.unity` | `MainMenuLifetimeScope` | ⚠️ planned | Menu presenter, art book entry. |
| `ColorBook.unity` | `ColorBookLifetimeScope` | ⚠️ planned | `PaperRig`, DrawingCatalog, ShapeBuilder, Coloring, History, Capture, ColorBookFlow. |
| `ArtBook.unity` | `ArtBookLifetimeScope` | ⚠️ planned | Gallery presenter, viewer, share. |

Only `Boot.unity` exists today; the three scene scope classes haven't been written yet either (only `RootLifetimeScope` exists in [App/LifetimeScopes/](Assets/Darkmatter/Code/App/LifetimeScopes/)).

Scopes nest: `Root → (MainMenu | ColorBook | ArtBook)`. Services resolved from the root parent. Scene scopes only register their own features.

### Boot chain (planned)

No `AppBoot` class exists yet — today `RootLifetimeScope` only registers services and stops there. When `AppBoot` is added (as an `IAsyncStartable` registered via `builder.RegisterEntryPoint<AppBoot>()`), it should run once, in order:

1. Initialize `IAssetProviderService` (Addressables init).
2. Preload essential bundles (palettes, UI sounds).
3. Load `IProgressionService` from disk.
4. Load `MainMenu` scene.

Failures show a child-friendly retry screen; never crash.

---

## 7. Rendering Strategy

**RT-as-paper.** ArtCamera renders the drawing world to an offscreen `RenderTexture`. A Canvas `RawImage` displays that RT. HUD lives on the same Canvas, above the RawImage. The RT *is* the paper — same fixed coordinate system on every device.

```
┌──────────────────────────────────────────────────────┐
│ UICanvas (Screen-Space - Camera, UICamera)          │
│                                                      │
│   ┌────────────────────────────────────┐             │
│   │ RawImage (AspectRatioFitter 1:1)   │   [HUD]    │
│   │  └─ texture = PaperRig.Surface     │   palette  │
│   │                                    │   undo etc │
│   │  ArtCamera renders → here          │             │
│   └────────────────────────────────────┘             │
│                                                      │
└──────────────────────────────────────────────────────┘
                       ▲
                       │  rendered offscreen
                       │
   ArtCamera (orthographicSize fixed, aspect = 1f)
       culling mask: Artwork, PaperBackground, Effects
       target texture: PaperRig.Surface (2048×2048 ARGB32)
```

### Cameras

| Camera | Type | Culling Mask | Render Target | Purpose |
|---|---|---|---|---|
| `ArtCamera` | Orthographic, **fixed ortho size**, aspect = 1 | `Artwork`, `PaperBackground`, `Effects` | `PaperRig.Surface` (offscreen RT) | Renders the drawing world. Never sees the screen. |
| `UICamera` | Camera (Screen-Space – Camera) | `UI` | Screen | Displays the paper RawImage + HUD. |

### Layers

| Layer | Used by |
|---|---|
| `Artwork` | Drawing region sprites, shape pieces, paper bg, all in ArtCamera world |
| `Effects` | Particle bursts, sparkles — also in ArtCamera world (so they're captured into the PNG) |
| `UI` | All Canvas elements (RawImage paper + HUD) |

### Why RT-as-paper

| Need | Choice | Why |
|---|---|---|
| Per-region tap-to-fill | Sprites + `PolygonCollider2D` in ArtCamera world; tapped via `IArtInputBridge` | Coordinate system is fixed (RT space). One `Physics2D.OverlapPoint` call after screen→art-world conversion. |
| Drag/drop shape pieces | Sprites + Physics2D in art world | Same fixed bounds on every device — no per-aspect tray layout. |
| Capture to PNG | `RT → Texture2D → PNG` | The RT *is* the saved image. No camera state override, no compositing pass, no determinism worries. |
| Multi-resolution support | `AspectRatioFitter (1:1, FitInParent)` on the RawImage | The "fit camera" problem reduces to a single Canvas property. Letterbox/pillarbox = whatever the Canvas around the RawImage looks like. |
| Color palette, buttons | Canvas above the RawImage | Anchors handle aspect ratios. Buttons + ScrollRect free. |
| Drawing catalog grid | Canvas | `GridLayoutGroup` + ScrollRect, async thumbnail loader. |

### Multi-resolution rule

The artwork world is **screen-size-independent by construction.** Author every drawing in a fixed 2048×2048 design rect (or 20×20 world units at PPU=100). Pieces, regions, snap radii, slot positions — all expressed in this space and never scaled at runtime. Different screen sizes only change how the *RawImage* is laid out on the Canvas; the contents of the RT stay identical.

If you need a backdrop (wood/cloth behind the paper), it's a sibling Canvas Image *outside* the RawImage, sized to fill the screen. The RT itself has a transparent or paper-colored background.

---

## 8. Core Contracts

All Core types are pure data or interfaces.

### Drawing

> Contracts live in `Darkmatter.Core.Contracts.Features.Drawing`; DTOs in `Darkmatter.Core.Data.Dynamic.Features.Drawing`.

```csharp
namespace Darkmatter.Core.Contracts.Features.Drawing;

public interface IDrawingTemplate {
    string Id { get; }
    string DisplayName { get; }
    Sprite Thumbnail { get; }
    Sprite PaperBackground { get; }
    IReadOnlyList<ShapePieceDTO> Pieces { get; }
    IReadOnlyList<ColorRegionDTO> Regions { get; }
}

public readonly struct ShapePieceDTO {
    public string PieceId { get; }
    public Sprite Sprite { get; }
    public Vector2 SlotPosition { get; }
    public float SlotRotation { get; }
    public float SnapRadius { get; }      // generous for toddlers
}

public readonly struct ColorRegionDTO {
    public string RegionId { get; }
    public Sprite Sprite { get; }          // sprite renderer source
    public Vector2[] ColliderPath { get; } // polygon collider points
    public Color InitialColor { get; }     // usually white
}
```

### Coloring

> Contracts in `Darkmatter.Core.Contracts.Features.Coloring`; DTOs in `Darkmatter.Core.Data.Dynamic.Features.Coloring`.

```csharp
namespace Darkmatter.Core.Contracts.Features.Coloring;

public interface IColorPalette {
    string Id { get; }
    IReadOnlyList<Color> Colors { get; }
}

public readonly struct PaintCommandDTO {
    public string RegionId { get; }
    public Color FromColor { get; }
    public Color ToColor { get; }
}
```

### Paper (RT rig + input bridge)

> Contracts live in `Darkmatter.Core.Contracts.Features.Paper`. Files at `Core/Contracts/Features/Paper/`.

```csharp
namespace Darkmatter.Core.Contracts.Features.Paper;

public interface IPaperRig {
    Camera ArtCamera { get; }              // offscreen, targetTexture = Surface
    RenderTexture Surface { get; }         // 2048×2048 ARGB32; the paper itself
    Transform PaperRoot { get; }           // parent of regions/pieces/paper bg
    Vector2 DesignSize { get; }            // world units, e.g. (20, 20)
    Rect DesignRect { get; }               // centered on origin, DesignSize wide
}

public interface IArtInputBridge {
    // Converts a screen-space pointer (Input System) to art-world coords
    // inside the RT. Returns false if the pointer is outside the RawImage.
    bool TryScreenToArtWorld(Vector2 screenPos, out Vector2 artWorldPos);
}
```

- `IPaperRig` is implemented by `PaperRig : MonoBehaviour` in the ColorBook scene.
- `IArtInputBridge` does the screen → RawImage local → UV → `ArtCamera.ViewportToWorldPoint` chain.
- All consumers (Coloring, ShapeBuilder, Capture, particle effects) read these from DI; they never touch `Screen.width/height` directly.

### History

> Contracts in `Darkmatter.Core.Contracts.Features.History`.

```csharp
namespace Darkmatter.Core.Contracts.Features.History;

public interface ICommand {
    void Execute();
    void Undo();
}

public interface IUndoStack {
    bool CanUndo { get; }
    bool CanRedo { get; }
    void Push(ICommand cmd);   // executes + appends
    void Undo();
    void Redo();
    void Clear();
}
```

### Gallery & Capture

> `IGalleryService` is a Service contract → `Darkmatter.Core.Contracts.Services.Gallery`. `SavedArtworkDTO` is a runtime data struct → `Darkmatter.Core.Data.Dynamic.Features.Gallery`. `ICaptureService` → `Darkmatter.Core.Contracts.Services.Capture`.

```csharp
namespace Darkmatter.Core.Data.Dynamic.Features.Gallery;

public readonly struct SavedArtworkDTO {
    public string Id { get; }
    public string TemplateId { get; }
    public DateTime CreatedUtc { get; }
    public string ImagePath { get; }       // persistentDataPath PNG
    public string ThumbnailPath { get; }
}

namespace Darkmatter.Core.Contracts.Services.Gallery;

public interface IGalleryService {
    UniTask<SavedArtworkDTO> SaveAsync(byte[] png, string templateId);
    UniTask<IReadOnlyList<SavedArtworkDTO>> ListAsync();
    UniTask<Texture2D> LoadFullAsync(string artworkId);
    UniTask DeleteAsync(string artworkId);
}

namespace Darkmatter.Core.Contracts.Services.Capture;

public interface ICaptureService {
    // No camera or paperBg args — capture reads directly from IPaperRig.Surface.
    // Dimensions inherited from the RT; no resize, no compositing.
    UniTask<byte[]> CaptureAsync();
}
```

`ICaptureService` resolves `IPaperRig` via DI and reads `Surface` directly. The paper background is already baked into the RT because it sits in `PaperRoot` under the ArtCamera. No special compositing pass is ever needed.

### Signals

> Signal structs live in `Darkmatter.Core.Data.Dynamic.Features.Signals` (runtime data, cross-feature).

```csharp
namespace Darkmatter.Core.Data.Dynamic.Features.Signals;

public readonly struct DrawingSelectedSignal {
    public string TemplateId { get; }
}

public readonly struct ShapeAssembledSignal {
    public string TemplateId { get; }
}

public readonly struct ColorAppliedSignal {
    public string RegionId { get; }
    public Color Color { get; }
}

public readonly struct ArtworkCapturedSignal {
    public string ArtworkId { get; }
}

public readonly struct ArtworkSavedSignal {
    public SavedArtworkDTO Artwork { get; }
}
```

---

## 9. Feature Responsibilities

### `DrawingCatalog`

- Loads the catalog manifest (list of available template IDs + thumbnail addresses).
- Presents a scrollable grid of thumbnails (Canvas).
- On select → fires `DrawingSelectedSignal(templateId)` and unloads the catalog UI.

### `Paper`

- Scene-scoped infrastructure. Lives in `ColorBook.unity` only.
- Owns `PaperRig` (MonoBehaviour) — exposes `ArtCamera`, the `RenderTexture Surface`, `PaperRoot` transform, and the design rect.
- Owns `ArtInputBridge` — converts pointer screen positions to art-world coords inside the RT.
- Registered in `ColorBookLifetimeScope` via `PaperRigModule`. All other features in the scene resolve `IPaperRig` / `IArtInputBridge` from DI.
- Lifetime is scene-scoped: created on scene load, destroyed on scene unload. RT is allocated in `Awake`, released in `OnDestroy`.

### `ShapeBuilder`

- Listens to `DrawingSelectedSignal`.
- Loads template via `IDrawingTemplateLoader`, parents shape pieces under `IPaperRig.PaperRoot` at off-slot positions inside the design rect.
- Per piece: drag with `ShapePieceView` (sprite + collider). Pointer events go through `IArtInputBridge.TryScreenToArtWorld`. On drop, check distance to `SlotPosition` against `SnapRadius`; if within, snap and lock.
- Fires `ShapeAssembledSignal` when all pieces locked.

### `Coloring`

- Listens to `ShapeAssembledSignal`.
- Spawns one `ColorRegionView` per `ColorRegionDTO` under `IPaperRig.PaperRoot` (sprite + polygon collider on `Artwork` layer).
- Listens to palette selection (current color held in `ColoringStateRepository`).
- On pointer down: `IArtInputBridge.TryScreenToArtWorld(screenPos, out var artPos)` → `Physics2D.OverlapPoint(artPos, artworkMask)` → if hit, build `PaintRegionCommand(regionId, oldColor, newColor)`, push to `IUndoStack`.
- Command sets `SpriteRenderer.color` on undo/redo.
- Fires `ColorAppliedSignal` for SFX / sparkle effects.

### `History`

- Owns the singleton `IUndoStack` for the current ColorBook session.
- Cleared on `DrawingSelectedSignal` (new drawing = fresh history).
- Capped at ~20 entries (memory + cognitive simplicity).
- UI: two big arrow buttons; disabled state when `CanUndo / CanRedo` is false.

### `Capture`

- Bound to the "Capture" button.
- Calls `ICaptureService.CaptureAsync()` → PNG bytes. Capture reads `IPaperRig.Surface` directly; no camera or paper-bg args needed.
- Hands bytes to `IGalleryService.SaveAsync(...)`.
- Fires `ArtworkCapturedSignal` then `ArtworkSavedSignal`.
- Shows a quick "saved!" toast with a thumbnail of the new entry.

### `Progression`

- Tracks completed template IDs and the in-progress draft.
- On "Next" button: silently runs Capture pipeline (auto-save), marks current as completed, calls `IDrawingTemplateCatalog.NextUnseen()`.
- Persists JSON via `IPersistenceService`.

### `ColorBookFlow`

- The only orchestrator inside ColorBook scope.
- Subscribes to flow-relevant signals and toggles UI panels (catalog → builder → coloring).
- Coordinates "Next" sequence: `IProgressionService.MarkCompleted` → `ICaptureService` autosave → `IDrawingTemplateLoader.Release(currentId)` → load next.
- Built as a small FSM (`Catalog → Building → Coloring → Done`).

### `ArtBook`

- Separate scene.
- `GalleryPresenter` calls `IGalleryService.ListAsync()` → grid of thumbnails.
- Tap → fullscreen view, share-sheet button, delete.
- Saved-to-device-camera-roll uses an optional platform plugin behind `IExternalShareService` (Core contract).

---

## 10. Addressables Strategy

Mirror the Bus Game pattern via `IAssetProviderService`.

### What ships through Addressables

| Asset | Why |
|---|---|
| `DrawingTemplate` ScriptableObject (per drawing) | Many; load on demand. |
| Shape piece sprites | Only needed when active. |
| Region sprites + polygon paths | Heavy; loaded per drawing. |
| Paper backgrounds | Per template, sometimes shared. |
| Color palette SOs | Swap per theme. |
| Audio clips (tap, snap, complete, sparkle) | Shared SFX bank. |

### What does NOT use Addressables

- HUD prefabs (palette button, undo icon) — always loaded with scene.
- Core UI canvases.
- Boot scene assets.
- User-saved gallery PNGs — those live in `Application.persistentDataPath`.

### Group layout

```
Drawings_Animals       (label: drawing, animals)
Drawings_Vehicles      (label: drawing, vehicles)
Drawings_Shapes        (label: drawing, shapes)
Palettes               (label: palette)
Audio_UI               (label: sfx, ui)
Audio_Coloring         (label: sfx, coloring)
```

### Lifecycle

- Catalog loads **thumbnail handles only** (cheap).
- On select → full template loads (pieces + regions + paper).
- On "Next" or scene exit → previous template `Release`d before next loads.
- This bound matters on toddler tablets with limited RAM.

### Remote groups (future)

Drawing packs ship as remote bundles. New theme packs (Christmas, Dinosaurs) update without an app store release.

---

## 11. Persistence

Two distinct stores, each behind its own Core contract.

### `IPersistenceService` (JSON / PlayerPrefs)

Holds:

- Completed template IDs.
- Last opened drawing.
- Audio volume, simple settings.

Path: `Application.persistentDataPath/save.json`.

### `IGalleryService` (file IO)

Holds user artworks:

```
persistentDataPath/Gallery/
├── {guid}.png            full-res render (~2048×2048)
├── {guid}.thumb.png      256×256 for grid
└── {guid}.json           SavedArtworkDTO sidecar
```

- Writes are atomic (`.tmp` → rename).
- `ListAsync` enumerates sidecar JSONs sorted by `CreatedUtc desc`.
- Thumbnail generation happens once at save time on a worker thread.

---

## 12. Capture Pipeline

With the RT-paper-rig, capture has no setup phase. The RT is already the final image at all times.

```
[Capture button or Next button]
        │
        ▼
ICaptureService.CaptureAsync()
        │
        ├─ rt = _paperRig.Surface             (already populated each frame)
        ├─ prev = RenderTexture.active
        ├─ RenderTexture.active = rt
        ├─ tex = new Texture2D(rt.width, rt.height, RGBA32, false)
        ├─ tex.ReadPixels(full rect, 0, 0); tex.Apply()
        ├─ RenderTexture.active = prev
        ├─ bytes = tex.EncodeToPNG()          (on worker via UniTask.RunOnThreadPool)
        ├─ Object.Destroy(tex)
        └─ return bytes
        ▼
IGalleryService.SaveAsync(bytes, templateId)
        │
        ├─ Write .png atomically
        ├─ Generate + write thumbnail
        ├─ Write sidecar JSON
        └─ return SavedArtworkDTO
        ▼
EventBus.Publish(new ArtworkSavedSignal(dto))
```

Notes:

- HUD never appears in capture because the HUD is on `UICamera` / Canvas — it is physically in a different render path. The RT only ever sees `ArtCamera`'s output.
- Paper background is a sprite parented under `IPaperRig.PaperRoot` and is rendered into the RT every frame — already baked in.
- Saved PNGs are byte-comparable across devices because the RT dimensions and ArtCamera matrix never depend on screen size.
- `CaptureAsync` is safe to call repeatedly — no camera state is ever mutated.

---

## 13. Communication Rules

| Use case | Mechanism |
|---|---|
| Load template, return result | Direct DI call (`IDrawingTemplateLoader.LoadAsync`). |
| Capture → save chain | Direct DI calls, sequenced. |
| Notify HUD that a region was painted | `IEventBus` signal. |
| Notify Progression that a drawing was completed | `IEventBus` signal. |
| Tell ColorBookFlow that pieces are assembled | `IEventBus` signal. |
| Tell Coloring which color is currently selected | Direct DI on `ColoringStateRepository`. |

**Never** use signals for request/response. If you need a return value or guaranteed single handler, define a Core interface.

---

## 14. UI (MVP — Passive View)

Identical to Bus Game.

- **Model** — controller / repository, fires C# events.
- **View** — `MonoBehaviour`, only setters (`SetColors(IReadOnlyList<Color>)`).
- **Presenter** — pure C#, subscribes to model events, calls view setters.

### Inspector bridge

For palette icons, undo buttons, region prefabs:

```csharp
[SerializeField, RequireInterface(typeof(IColorButtonView))]
private MonoBehaviour[] _colorButtons;
```

---

## 15. Toddler UX Constraints

These shape several design decisions and are **non-negotiable**:

- **No fail states.** Drawings cannot be "wrong".
- **No timers.** Nothing decays or runs out.
- **No tiny hitboxes.** Drag tolerance ≥ 40 px; snap radius ≥ 60 px for shape pieces.
- **Auto-snap on near-miss.** If a piece is dropped within `1.5 × SnapRadius`, snap anyway and play a happy sound.
- **No text-heavy UI.** Icons everywhere. Single-word labels max.
- **Loud, immediate feedback.** Every tap plays a sound; every fill bursts a small particle effect.
- **Undo cap = 20.** Toddlers will mash undo. Bound the memory.
- **Long-press = quick menu off.** Avoid surprise modals.

---

## 16. Testing

| Layer | Test type | Location |
|---|---|---|
| `Libs/CommandStack` | EditMode unit tests | `Libs/CommandStack/Tests/` |
| `Core` DTOs | EditMode | rarely needed, but for `SavedArtworkDTO` serialization, yes. |
| `Services/Gallery` | EditMode w/ temp directory | mocks `Application.persistentDataPath`. |
| `Services/Capture` | PlayMode | requires a Camera in the test scene. |
| `Features/*/Systems` | EditMode w/ DI test container | inject fakes for `IUndoStack`, signals captured by a fake `IEventBus`. |
| Full flow | PlayMode smoke test | one drawing → assemble → color → capture → assert gallery has 1 file. |

---

## 17. "Where do I put this?" Checklist

1. **Is it a cross-assembly interface / enum / DTO?** → `Core/`
2. **Is it a generic, sellable utility?** → `Libs/`
3. **Is it infrastructure (input, audio, file IO, addressables, capture)?** → `Services/`
4. **Is it gameplay logic specific to coloring books?** → `Features/`
5. **Is it composition / scene wiring?** → `App/`

When in doubt, ask: *would deleting this feature break Core?* If yes, the dependency is wrong.

---

## 18. Open Questions / Future Work

- **Pencil/brush mode** — currently the design is tap-to-fill regions. A free-draw brush mode would need a `BrushStrokeCommand` and a dynamic texture per region; out of scope for v1.
- **Multi-child profiles** — single-profile for v1; multi-profile would slot in behind `IProgressionService` and `IGalleryService` keyed by `profileId`.
- **Cloud sync** — gallery sync would happen behind `IGalleryService` (decorator pattern); local-first stays the source of truth.
- **Sticker / decoration layer** — additive sprite layer above coloring, also `ICommand`-driven so it integrates with undo/redo cleanly.

---

## 19. Quick Reference — Feature ↔ Signal Map

| Feature | Subscribes to | Publishes |
|---|---|---|
| `DrawingCatalog` | — | `DrawingSelectedSignal` |
| `ShapeBuilder` | `DrawingSelectedSignal` | `ShapeAssembledSignal` |
| `Coloring` | `ShapeAssembledSignal` | `ColorAppliedSignal` |
| `History` | `DrawingSelectedSignal` (to clear) | — |
| `Capture` | — (button-driven) | `ArtworkCapturedSignal`, `ArtworkSavedSignal` |
| `Progression` | `ArtworkSavedSignal` | — |
| `ColorBookFlow` | `ShapeAssembledSignal`, `ArtworkSavedSignal` | — |
| `ArtBook (Gallery)` | `ArtworkSavedSignal` (if open) | — |

---

Maintained alongside the [Darkmatter Architecture Guide](../Assets/Darkmatter_Architecture_Guide.md). Do not break the dependency arrows.

---

## 20. Assembly Definition Map

Every Lib / Service / Feature is its own `.asmdef`. The `Darkmatter.` prefix is **only** on the App asmdef; everything else uses bare `<Layer>.<Module>` names. References follow the layer rules.

### On disk today

| Asmdef | Path | References |
|---|---|---|
| `Darkmatter.App` | `App/` | All Services, Libs, Core (Features when they land) |
| `Core` | `Core/` | (none — `UniTask` allowed in async signatures) |
| `Libs.FSM` | `Libs/FSM/` | `Core` |
| `Libs.Installers` | `Libs/Installers/` | (VContainer only) |
| `Libs.Observer` | `Libs/Observer/` | `Core` |
| `Libs.PlayerPrefs` | `Libs/PlayerPrefs/Runtime/` | (standalone) |
| `Libs.PlayerPrefs.Editor` | `Libs/PlayerPrefs/Editor/` | `Libs.PlayerPrefs` |
| `Libs.UI` | `Libs/UI/` | `Core` |
| `Services.Analytics` | `Services/Analytics/` | `Core`, `Libs.Installers` |
| `Services.Assets` | `Services/Assets/` | `Core`, `Libs.Installers` |
| `Services.Audio` | `Services/Audio/` | `Core`, `Libs.Installers` |
| `Services.Camera` | `Services/Camera/` | `Core`, `Libs.Installers` |
| `Services.Inputs` | `Services/Inputs/` | `Core`, `Libs.Installers` |
| `Services.Scenes` | `Services/Scenes/` | `Core`, `Libs.Installers` |

### Planned (not on disk yet)

| Asmdef | Path | References |
|---|---|---|
| `Libs.CommandStack` | `Libs/CommandStack/` | `Core` |
| `Services.Capture` | `Services/Capture/` | `Core`, `Libs.Installers` |
| `Services.Gallery` | `Services/Gallery/` | `Core`, `Libs.Installers` |
| `Features.Paper` | `Features/Paper/` | `Core`, `Libs.Installers` |
| `Features.MainMenu` | `Features/MainMenu/` | `Core`, `Libs.Installers` |
| `Features.DrawingCatalog` | `Features/DrawingCatalog/` | `Core`, `Libs.Installers` |
| `Features.ShapeBuilder` | `Features/ShapeBuilder/` | `Core`, `Libs.Installers` |
| `Features.Coloring` | `Features/Coloring/` | `Core`, `Libs.Installers`, `Libs.CommandStack` |
| `Features.History` | `Features/History/` | `Core`, `Libs.Installers`, `Libs.CommandStack` |
| `Features.Capture` | `Features/Capture/` | `Core`, `Libs.Installers` |
| `Features.Progression` | `Features/Progression/` | `Core`, `Libs.Installers`, `Libs.PlayerPrefs` |
| `Features.ColorBookFlow` | `Features/ColorBookFlow/` | `Core`, `Libs.Installers`, `Libs.FSM` |
| `Features.ArtBook` | `Features/ArtBook/` | `Core`, `Libs.Installers` |

**Hard rules:**
- No Service asmdef references any Feature asmdef.
- No Feature asmdef references another Feature asmdef.
- All Services and Features depend on `Libs.Installers` so they can implement `IServiceModule`.
- The compiler enforces this — if a `using` won't resolve, the dependency is wrong.

---

## 21. LifetimeScope Concrete Sample

All scopes use the same pattern: a serialized `MonoBehaviour[]` list of `IServiceModule` installers. Each installer is a MonoBehaviour on a child GameObject of the scope. Scope iterates and calls `Register`. **No hardcoded registrations in the scope itself.** This is exactly what [RootLifetimeScope.cs](Assets/Darkmatter/Code/App/LifetimeScopes/RootLifetimeScope.cs) already does today.

### `RootLifetimeScope` (Boot scene, persists forever) — actual code

```csharp
using Darkmatter.Libs.Installers;
using UnityEngine;
using VContainer;
using VContainer.Unity;

public class RootLifetimeScope : LifetimeScope {
    [SerializeField] private MonoBehaviour[] serviceModules;

    protected override void Configure(IContainerBuilder builder) {
        foreach (var module in serviceModules) {
            if (module is IServiceModule serviceModule)
                serviceModule.Register(builder);
        }
    }
}
```

The inspector lists the installer MonoBehaviours in `serviceModules[]`. Drag the children of the Boot scope GameObject (e.g. `AudioServiceModule`, `CameraServiceModule`, `InputServiceModule`, `AssetProviderServiceModule`, `AnalyticsServiceModule`, `SceneServiceModule`) into that slot. Each is a `MonoBehaviour, IServiceModule`.

### `ColorBookLifetimeScope` (per-scene, child of Root) — same pattern

```csharp
namespace Darkmatter.App.LifetimeScopes;

public sealed class ColorBookLifetimeScope : LifetimeScope {
    [SerializeField] private MonoBehaviour[] sceneModules;

    protected override void Configure(IContainerBuilder builder) {
        foreach (var module in sceneModules) {
            if (module is IServiceModule serviceModule)
                serviceModule.Register(builder);
        }
    }
}
```

Drag the scene's installer MonoBehaviours into `sceneModules[]`:
- `PaperRigModule`
- `DrawingCatalogModule`
- `ShapeBuilderModule`
- `ColoringModule`
- `HistoryModule`
- `CaptureModule`
- `ProgressionModule`
- `ColorBookFlowModule`

Each registers its own classes via `IServiceModule.Register(IContainerBuilder)`.

> If a scope needs a non-installer reference (e.g. a `ColorBookSceneRefs` MB holding camera + roots), expose it as a separate `[SerializeField]` and `builder.RegisterInstance(...)` it inside the scope's `Configure`. Don't put scene refs inside an installer — keep installers stateless across scenes.

---

## 22. Installer Pattern — Concrete Coloring Sample

Mirrors the existing [CameraServiceModule.cs](Assets/Darkmatter/Code/Services/Camera/Installers/CameraServiceModule.cs) and [InputServiceModule.cs](Assets/Darkmatter/Code/Services/Inputs/Installers/InputServiceModule.cs) — a `MonoBehaviour` implementing `IServiceModule.Register`.

```csharp
namespace Darkmatter.Features.Coloring.Installers;

public sealed class ColoringModule : MonoBehaviour, IServiceModule {
    [SerializeField] private ColoringConfig _config;

    public void Register(IContainerBuilder builder) {
        builder.RegisterInstance(_config);
        builder.Register<ColoringStateRepository>(Lifetime.Scoped).AsSelf();
        builder.Register<ColoringController>(Lifetime.Scoped)
               .As<IColoringController>()
               .AsSelf();
        builder.Register<ColorPalettePresenter>(Lifetime.Scoped).AsSelf();
        builder.RegisterEntryPoint<ColoringInputBinder>();
    }
}
```

Convention:
- One `IServiceModule` per feature, named `<Feature>Module` (matches `CameraServiceModule`, `InputServiceModule`, `AnalyticsServiceModule` already in the project).
- `MonoBehaviour` lives on a GameObject under the scope's hierarchy; dragged into the scope's `serviceModules[]` / `sceneModules[]` inspector list.
- Method name is `Register`, not `Install`. There is **no `IInstaller`** in this project — uses `IServiceModule` from [Libs.Installers](Assets/Darkmatter/Code/Libs/Installers/IServiceModule.cs).
- Registers only its own types. Never touches another feature's types.
- If the installer needs to wire scene-bound MonoBehaviours into DI, expose them as `[SerializeField]` fields on the installer itself and `builder.RegisterInstance<IFoo>(_foo)` them. See the planned `PaperRigModule` in §32.5b for an example.

---

## 23. Command Pattern — `PaintRegionCommand`

```csharp
namespace Darkmatter.Features.Coloring.Commands;

internal sealed class PaintRegionCommand : ICommand {
    private readonly ColorRegionView _view;
    private readonly Color _fromColor;
    private readonly Color _toColor;
    private readonly IEventBus _bus;

    public PaintRegionCommand(ColorRegionView view, Color from, Color to, IEventBus bus) {
        _view = view;
        _fromColor = from;
        _toColor = to;
        _bus = bus;
    }

    public void Execute() {
        _view.SetColor(_toColor);
        _bus.Publish(new ColorAppliedSignal(_view.RegionId, _toColor));
    }

    public void Undo() {
        _view.SetColor(_fromColor);
        _bus.Publish(new ColorAppliedSignal(_view.RegionId, _fromColor));
    }
}
```

Usage in controller:

```csharp
public void PaintRegion(ColorRegionView view) {
    var current = _state.CurrentColor;
    if (view.Color == current) return;            // no-op
    var cmd = new PaintRegionCommand(view, view.Color, current, _bus);
    _undoStack.Push(cmd);                          // Push executes + records
}
```

Same pattern applies to `SnapPieceCommand` if shape-builder steps should be undoable (optional for v1).

---

## 24. CommandStack — `Libs/CommandStack`

```csharp
namespace Darkmatter.Lib.CommandStack;

public sealed class BoundedUndoStack : IUndoStack {
    private readonly Deque<ICommand> _undo = new();
    private readonly Stack<ICommand> _redo = new();
    private readonly int _capacity;

    public BoundedUndoStack(int capacity = 20) => _capacity = capacity;

    public bool CanUndo => _undo.Count > 0;
    public bool CanRedo => _redo.Count > 0;

    public void Push(ICommand cmd) {
        cmd.Execute();
        _undo.AddLast(cmd);
        if (_undo.Count > _capacity) _undo.RemoveFirst();
        _redo.Clear();
    }

    public void Undo() {
        if (!CanUndo) return;
        var cmd = _undo.Last;
        _undo.RemoveLast();
        cmd.Undo();
        _redo.Push(cmd);
    }

    public void Redo() {
        if (!CanRedo) return;
        var cmd = _redo.Pop();
        cmd.Execute();
        _undo.AddLast(cmd);
    }

    public void Clear() {
        _undo.Clear();
        _redo.Clear();
    }
}
```

`Deque<T>` keeps the oldest entry cheap to evict when the cap fires.

---

## 25. View / Presenter Pair — Color Palette

### View (MonoBehaviour, setters only)

```csharp
namespace Darkmatter.Features.Coloring.UI;

public sealed class ColorPaletteView : MonoBehaviour, IColorPaletteView {
    [SerializeField, RequireInterface(typeof(IColorButtonView))]
    private MonoBehaviour[] _buttonsRaw;

    private IColorButtonView[] _buttons;

    public event Action<int> OnColorButtonClicked;

    private void Awake() {
        _buttons = _buttonsRaw.Cast<IColorButtonView>().ToArray();
        for (var i = 0; i < _buttons.Length; i++) {
            var idx = i;
            _buttons[i].OnClicked += () => OnColorButtonClicked?.Invoke(idx);
        }
    }

    public void SetColors(IReadOnlyList<Color> colors) {
        for (var i = 0; i < _buttons.Length; i++)
            _buttons[i].SetVisible(i < colors.Count);
        for (var i = 0; i < colors.Count; i++)
            _buttons[i].SetColor(colors[i]);
    }

    public void SetSelected(int index) {
        for (var i = 0; i < _buttons.Length; i++)
            _buttons[i].SetSelected(i == index);
    }
}
```

### Presenter (pure C#)

```csharp
namespace Darkmatter.Features.Coloring.UI;

public sealed class ColorPalettePresenter : IStartable, IDisposable {
    private readonly IColorPaletteView _view;
    private readonly ColoringStateRepository _state;

    public ColorPalettePresenter(IColorPaletteView view, ColoringStateRepository state) {
        _view = view;
        _state = state;
    }

    public void Start() {
        _view.SetColors(_state.Palette.Colors);
        _view.SetSelected(_state.SelectedIndex);
        _view.OnColorButtonClicked += OnClicked;
        _state.SelectedIndexChanged += OnIndexChanged;
    }

    private void OnClicked(int index) => _state.SelectColor(index);
    private void OnIndexChanged(int index) => _view.SetSelected(index);

    public void Dispose() {
        _view.OnColorButtonClicked -= OnClicked;
        _state.SelectedIndexChanged -= OnIndexChanged;
    }
}
```

Same shape repeats for every feature's UI.

---

## 26. ShapeBuilder — Snap Algorithm

```csharp
// In ShapePieceView.OnPointerUp:
public void OnDragEnd(Vector2 worldPos) {
    var slot = transform.position;            // assigned target slot
    var d = Vector2.Distance(worldPos, slot);

    if (d <= _piece.SnapRadius) {
        SnapToSlot();
    } else if (d <= _piece.SnapRadius * 1.5f) {
        // Toddler grace zone — snap anyway, play happy sound
        SnapToSlot();
        _audio.PlayOneShot(_clips.NiceTry);
    } else {
        ReturnToTrayAnimated();
    }
}

private void SnapToSlot() {
    _locked = true;
    transform.DOMove(_piece.SlotPosition, 0.25f).SetEase(Ease.OutBack);
    _audio.PlayOneShot(_clips.Snap);
    _bus.Publish(new PieceSnappedSignal(_piece.PieceId));
}
```

Controller listens for `PieceSnappedSignal`, counts against expected piece count, fires `ShapeAssembledSignal` when complete.

---

## 27. Rendering Order & Sorting

URP 2D with a single `ArtCamera` ortho cam.

| Sorting Layer | Order | Contents |
|---|---|---|
| `PaperBackground` | 0 | Paper bg sprite (under everything) |
| `ArtworkRegions` | 100 | `ColorRegionView` sprites (the colorable shapes) |
| `ArtworkPieces` | 200 | `ShapePieceView` sprites (during build) |
| `Effects` | 300 | Particle bursts, sparkles |
| `UIWorld` | 400 | World-space prompts (rare; mostly Canvas) |

Canvas HUD lives on `UICamera` (Overlay), never sorts against `ArtCamera`. Capture renders only `ArtCamera`'s layers → HUD physically cannot leak into saved PNG.

---

## 28. SavedArtwork JSON Schema

```json
{
  "id": "f3a8e2d4-...",
  "templateId": "animals/elephant",
  "createdUtc": "2026-05-26T16:42:11Z",
  "imagePath": "Gallery/f3a8e2d4-....png",
  "thumbnailPath": "Gallery/f3a8e2d4-....thumb.png",
  "regions": [
    { "regionId": "body", "color": "#FFB347" },
    { "regionId": "ears", "color": "#FF6961" }
  ]
}
```

`regions[]` lets the gallery reopen an artwork for further edits in a future version (out of scope v1, but the schema reserves the field now to avoid migration later).

Paths are **relative** to `persistentDataPath`. Never store absolute paths — they change between OS updates on some platforms.

---

## 29. Boot & Error Handling

```
AppBoot.StartAsync()
  ├─ try Addressables.InitializeAsync()
  │     fail → show "Tap to retry" splash
  ├─ try preload palette + UI sounds (Addressables labels)
  │     fail → log + continue (non-fatal)
  ├─ try _persistence.LoadAsync()
  │     fail → start with empty progression (don't crash)
  ├─ _scenes.LoadAsync("MainMenu")
  └─ done
```

Toddler-mode error UI:
- One large smiling icon.
- One big "tap" button.
- No text, no error codes.
- A small upper-right gear opens a parent-only diagnostic screen (long-press 3 s to unlock).

---

## 30. Setup Checklist (new dev, day one)

1. Open `Colorbook.sln` at the repo root.
2. Open `Assets/Darkmatter/Scenes/Boot.unity` (currently the only scene wired).
3. Inspect the `RootLifetimeScope` GameObject — confirm its `serviceModules[]` list references the child installer MonoBehaviours (`AudioServiceModule`, `CameraServiceModule`, `InputServiceModule`, etc.).
4. Hit Play from `Boot.unity`. Other scenes (`MainMenu`, `ColorBook`, `ArtBook`) don't exist yet — they're listed in §6 / §4c as planned work.
5. When new scene scopes land, the same rule applies: never start a scene mid-flow, always enter from `Boot.unity` so the root scope exists.
6. When drawings are authored: duplicate the template folder under `Content/Gameplay/Drawings/<theme>/<id>/`, edit `Template.asset` (pieces + regions), add to the appropriate Addressables group.
7. Run `Tests > EditMode` and `Tests > PlayMode` before pushing (test infra not set up yet — see §16).

---

## 31. Quick Reference — Class ↔ Layer ↔ Asmdef

| Class | Layer | Asmdef |
|---|---|---|
| `IDrawingTemplate`, `ShapePieceDTO`, `ColorRegionDTO` | Core | `Core` |
| `IPaperRig`, `IArtInputBridge` | Core | `Core` |
| `ICommand`, `IUndoStack` | Core | `Core` |
| `BoundedUndoStack` | Libs | `Libs.CommandStack` |
| `AddressableAssetProviderService` | Services | `Services.Assets` |
| `FileGalleryService` | Services | `Services.Gallery` |
| `RenderTextureCaptureService` | Services | `Services.Capture` |
| `PaperRig`, `ArtInputBridge`, `PaperRigModule` | Features | `Features.Paper` |
| `ColoringController`, `PaintRegionCommand` | Features | `Features.Coloring` |
| `ShapeBuilderController`, `ShapePieceView` | Features | `Features.ShapeBuilder` |
| `HistoryController` | Features | `Features.History` |
| `ColorBookFlowController` | Features | `Features.ColorBookFlow` |
| `GalleryPresenter`, `GalleryGridView` | Features | `Features.ArtBook` |
| `ColorBookLifetimeScope`, `AppBoot` | App | `Darkmatter.App` |

If a class's natural home doesn't match its asmdef, the architecture is bent — fix the placement, don't add a reference.

---

## 32. Class Reference (Detailed)

Canonical breakdown of every concrete class and interface. For each: **purpose**, **public surface** (signatures), **injected dependencies**, and **collaborators** (signals or interfaces it talks to).

> Convention used below
> - `// fields:` = constructor-injected dependencies
> - `// pub:` = events / signals fired
> - `// sub:` = events / signals consumed
> - All async returns are `UniTask` unless noted.

---

### 32.1 Core Contracts

Pure interfaces and DTOs. Zero logic.

#### `IDrawingTemplate` *(Core/Drawing)*
Immutable view of a single drawing's authored data.
```csharp
public interface IDrawingTemplate {
    string Id { get; }                              // e.g. "animals/elephant"
    string DisplayName { get; }                     // user-facing
    Sprite Thumbnail { get; }                       // 256×256 for catalog grid
    Sprite PaperBackground { get; }                 // composited under artwork
    IReadOnlyList<ShapePieceDTO> Pieces { get; }    // for ShapeBuilder
    IReadOnlyList<ColorRegionDTO> Regions { get; }  // for Coloring
}
```
Implemented by `DrawingTemplateSO` (ScriptableObject) loaded via Addressables.

#### `IDrawingTemplateCatalog` *(Core/Drawing)*
Authority on which drawings exist, completion state, and "next" selection.
```csharp
public interface IDrawingTemplateCatalog {
    UniTask InitializeAsync();                       // pulls manifest from Addressables
    IReadOnlyList<string> AllTemplateIds { get; }
    UniTask<Sprite> GetThumbnailAsync(string id);    // cheap; for grid
    UniTask<IDrawingTemplate> LoadAsync(string id);  // expensive; full template
    void Release(string id);                         // Addressables ref count down
    string NextUnseen(string currentId);             // progression hint
}
```

#### `IColorPalette` *(Core/Coloring)*
Set of colors offered to the child. Authored as `ColorPaletteSO`.
```csharp
public interface IColorPalette {
    string Id { get; }
    IReadOnlyList<Color> Colors { get; }             // 6–10 entries typical
}
```

#### `ICommand` & `IUndoStack` *(Core/History)*
Already shown in section 8. Each undoable user action is one `ICommand`; the stack is bounded.

#### `IGalleryService` *(Core/Gallery)*
Persistent store of saved artwork PNGs.
```csharp
public interface IGalleryService {
    UniTask<SavedArtworkDTO> SaveAsync(byte[] png, string templateId);
    UniTask<IReadOnlyList<SavedArtworkDTO>> ListAsync();   // sorted newest first
    UniTask<Texture2D> LoadFullAsync(string artworkId);    // for fullscreen view
    UniTask<Texture2D> LoadThumbnailAsync(string artworkId);
    UniTask DeleteAsync(string artworkId);
}
```

#### `ICaptureService` *(Core/Capture)*
Snapshots the paper RT to a PNG blob. No arguments — dimensions and content come from `IPaperRig.Surface`.
```csharp
public interface ICaptureService {
    UniTask<byte[]> CaptureAsync();
}
```

#### `IPaperRig` *(Core/Paper)*
Shared art rig. The single source of truth for everything that lives in the drawing world.
```csharp
public interface IPaperRig {
    Camera ArtCamera { get; }              // offscreen, targetTexture = Surface
    RenderTexture Surface { get; }         // 2048×2048 ARGB32 — the paper itself
    Transform PaperRoot { get; }           // parent of regions/pieces/paper bg
    Vector2 DesignSize { get; }            // world units, e.g. (20, 20)
    Rect DesignRect { get; }               // centered on origin
}
```

#### `IArtInputBridge` *(Core/Paper)*
Converts screen-space pointer coords to art-world coords inside the RT.
```csharp
public interface IArtInputBridge {
    bool TryScreenToArtWorld(Vector2 screenPos, out Vector2 artWorldPos);
}
```
Returns `false` when the pointer is outside the displayed RawImage rect (toddler tapped the HUD or backdrop). Every art-world raycast goes through this.

#### `IProgressionService` *(Core/Progression)*
Tracks which templates the child has completed and what they last opened.
```csharp
public interface IProgressionService {
    UniTask LoadAsync();
    UniTask SaveAsync();
    IReadOnlyCollection<string> CompletedTemplateIds { get; }
    string LastOpenedTemplateId { get; }
    void MarkCompleted(string templateId);
    void SetLastOpened(string templateId);
}
```

#### `IAssetProviderService` *(Core/Assets)*
Addressables wrapper. Hides handle bookkeeping from features.
```csharp
public interface IAssetProviderService {
    UniTask InitializeAsync();
    UniTask<T> LoadAsync<T>(string address) where T : UnityEngine.Object;
    UniTask<IReadOnlyList<T>> LoadByLabelAsync<T>(string label) where T : UnityEngine.Object;
    void Release(string address);
    void ReleaseAll();
}
```

#### `IEventBus` *(Libs/EventBus, also referenced from Core)*
```csharp
public interface IEventBus {
    void Publish<T>(T signal) where T : struct;
    IDisposable Subscribe<T>(Action<T> handler) where T : struct;
}
```
Signals are structs to avoid GC. Disposable subscription so presenters can unsubscribe in `Dispose()`.

---

### 32.2 Services Layer

Concrete infrastructure. One implementation each. All singletons in `RootLifetimeScope`.

#### `AddressableAssetProviderService` *(Services/Assets)*
Implements `IAssetProviderService`.
- **Responsibility:** Wrap `Addressables.LoadAssetAsync<T>` and ref-count handles by address.
- **State:** `Dictionary<string, AsyncOperationHandle>` keyed by address.
- **Notes:** `Release(address)` decrements; `ReleaseAll()` for scene teardown. Initialization must complete before any other service may load.

#### `FileGalleryService` *(Services/Gallery)*
Implements `IGalleryService`.
```csharp
// fields:
//   IPathProvider _paths           (wraps Application.persistentDataPath for tests)
//   IThumbnailGenerator _thumb     (downscale + encode)
//   IEventBus _bus
// pub: ArtworkSavedSignal, ArtworkDeletedSignal
```
- **Save flow:** write `{guid}.png.tmp` → fsync → rename; generate thumbnail on a worker; write sidecar JSON last (so partial saves are detectable by absence of JSON).
- **List flow:** enumerate `*.json` in `Gallery/`, deserialize, sort by `CreatedUtc desc`.
- **Delete flow:** delete png + thumb + json; missing files ignored (idempotent).

#### `RenderTextureCaptureService` *(Services/Capture)*
Implements `ICaptureService`.
- **Steps:** allocate `RenderTexture(width, height, 0, ARGB32)` → bind to `artCamera.targetTexture` → `artCamera.Render()` → `ReadPixels` into `Texture2D` → composite `paperBackground` underneath (single shader blit) → `EncodeToPNG` → release RT + textures.
- **Threading:** PNG encode happens on a `UniTask.RunOnThreadPool` to avoid hitching the main thread on tablets.
- **Sizing:** default 2048², overridable. Capped at device max texture size.

#### `JsonPersistenceService` *(Services/Persistence)*
Implements `IPersistenceService` (small JSON blob; not the gallery).
```csharp
public interface IPersistenceService {
    UniTask<T> LoadAsync<T>(string key) where T : class, new();
    UniTask SaveAsync<T>(string key, T value);
}
```
- **Path:** `Application.persistentDataPath/save.json`.
- **Format:** single JSON object keyed by `key` so multiple services can share one file.
- **Atomicity:** write to `save.json.tmp` → rename.

#### `SceneService` *(Services/Scenes)*
Implements `ISceneService`. Wraps `SceneManager.LoadSceneAsync` with `UniTask` plus a fade-curtain.
```csharp
public interface ISceneService {
    UniTask LoadAsync(string sceneName, LoadSceneMode mode = LoadSceneMode.Single);
    UniTask UnloadAsync(string sceneName);
}
```

#### `AudioService` *(Services/Audio)*
Implements `IAudioService`. Plays SFX clips loaded by address, mixes via Unity AudioMixer groups.
```csharp
public interface IAudioService {
    UniTask PreloadAsync(string label);              // e.g. "sfx,ui"
    void PlayOneShot(string clipId, float volume = 1f);
    void SetCategoryVolume(AudioCategory cat, float v01);
}
```
Holds an internal `Dictionary<string, AudioClip>` populated at preload.

#### `InputReaderSO` *(Services/Inputs)*
ScriptableObject wrapping the new Input System; exposes events.
```csharp
public interface IInputReader {
    event Action<Vector2> PointerDown;     // world pos
    event Action<Vector2> PointerDrag;
    event Action<Vector2> PointerUp;
}
```
- **Why an SO:** assignable in inspector and survives scene loads, but still resolvable via DI (`builder.RegisterInstance(_inputReader).As<IInputReader>()`).

---

### 32.3 Libs

Generic, project-agnostic utilities.

#### `BoundedUndoStack` *(Libs/CommandStack)*
Implements `IUndoStack`. Source already in section 24.
- **Capacity:** default 20.
- **Invariant:** `_redo` cleared on any new `Push`.
- **Edge cases:** `Undo`/`Redo` on empty stack is a no-op (never throws).

#### `EventBus` *(Libs/EventBus)*
Implements `IEventBus` with a `Dictionary<Type, Delegate>` of `Action<T>` per signal type.
- **Subscribe** returns an `IDisposable` that removes the handler on `Dispose`.
- **Publish** snapshots the invocation list before iterating (so handlers may safely unsubscribe during dispatch).

#### `Fsm<TState>` *(Libs/FSM)*
Generic state machine used by `ColorBookFlowController`.
```csharp
public sealed class Fsm<TState> where TState : struct, Enum {
    public TState Current { get; }
    public event Action<TState, TState> Transitioned;
    public void Bind(TState state, IFsmState handler);
    public void Go(TState next);                     // calls Exit on old, Enter on new
}

public interface IFsmState { void Enter(); void Exit(); }
```

---

### 32.4 Feature — `DrawingCatalog`

#### `DrawingCatalogController` *(Systems)*
Headless logic. Owns the list of template IDs visible in the grid.
```csharp
// fields: IDrawingTemplateCatalog _catalog, IEventBus _bus
public sealed class DrawingCatalogController : IAsyncStartable {
    public IReadOnlyList<string> VisibleIds { get; }
    public event Action ListChanged;
    public UniTask StartAsync(CancellationToken ct);     // pulls catalog, refreshes list
    public void OnTemplateSelected(string id);           // bus.Publish(new DrawingSelectedSignal(id))
}
// pub: DrawingSelectedSignal
```

#### `DrawingCatalogPresenter` *(UI)*
Bridges controller ↔ view.
```csharp
// fields: IDrawingCatalogView _view, DrawingCatalogController _ctrl, IDrawingTemplateCatalog _catalog
public sealed class DrawingCatalogPresenter : IStartable, IDisposable {
    public void Start();         // wires view.OnItemClicked → _ctrl.OnTemplateSelected
    public void Dispose();
}
```
- **Thumbnail load:** `_catalog.GetThumbnailAsync(id)` per visible cell, with placeholder while loading.

#### `DrawingCatalogView : MonoBehaviour` *(UI)*
Implements `IDrawingCatalogView`. Pure setters + click event.
```csharp
public interface IDrawingCatalogView {
    event Action<string> OnItemClicked;
    void SetItems(IReadOnlyList<CatalogItemVM> items);   // vm = id + Sprite thumbnail
}
```

---

### 32.5 Feature — `ShapeBuilder`

#### `ShapeBuilderController` *(Systems)*
Spawns shape pieces for the selected template, tracks snap progress, fires `ShapeAssembledSignal` when complete.
```csharp
// fields: IDrawingTemplateCatalog _catalog, ShapePieceFactory _factory, IEventBus _bus, ShapeBuilderConfig _cfg
public sealed class ShapeBuilderController : IDisposable {
    public IReadOnlyList<ShapePieceView> Active { get; }
    public UniTask BuildAsync(string templateId);    // load template, spawn pieces in tray
    public void Reset();                             // clear, unsubscribe
}
// sub: DrawingSelectedSignal
// pub: ShapeAssembledSignal
```
- **Internal:** counts `PieceSnappedSignal` against expected piece count.

#### `ShapePieceView : MonoBehaviour` *(Views)*
World-space draggable sprite with collider. Source for snap-or-return logic shown in section 26.
```csharp
public sealed class ShapePieceView : MonoBehaviour {
    public string PieceId { get; }
    public bool IsLocked { get; }
    public event Action<string> Snapped;             // raised when piece locks into slot
    public void Initialize(ShapePieceDTO dto, IInputReader input, IAudioService audio);
}
```
- **No public mutators** for position once locked — controller treats `IsLocked` as the source of truth.

#### `ShapePieceFactory` *(Systems)*
Instantiates `ShapePieceView` prefabs from a pool. Avoids re-instantiating across "Next" cycles on the same template family.
```csharp
public sealed class ShapePieceFactory {
    public ShapePieceView Spawn(ShapePieceDTO dto, Transform parent);
    public void Despawn(ShapePieceView view);
}
```

---

### 32.5b Feature — `Paper`

The shared art rig — RT, offscreen camera, screen↔world bridge. Every other feature in the ColorBook scene resolves `IPaperRig` and `IArtInputBridge` from DI and never touches `Screen.*` or `Camera.*` directly.

#### `PaperRig : MonoBehaviour, IPaperRig` *(Rig)*
Scene-bound component placed on a GameObject in `ColorBook.unity`. Owns the RT lifecycle.
```csharp
// inspector fields:
//   Camera _artCamera                  (Orthographic, aspect=1, fixed ortho size)
//   Transform _paperRoot               (parent of regions/pieces)
//   Vector2  _designSize = (20, 20)    (world units; matches 2048×2048 at PPU=100)
//   int      _surfaceSize = 2048       (RT side length, square)

public sealed class PaperRig : MonoBehaviour, IPaperRig {
    public Camera ArtCamera => _artCamera;
    public RenderTexture Surface => _surface;
    public Transform PaperRoot => _paperRoot;
    public Vector2 DesignSize => _designSize;
    public Rect DesignRect => new(-_designSize / 2f, _designSize);
}
```
- **Awake:** allocate `_surface = new RenderTexture(_surfaceSize, _surfaceSize, 0, ARGB32) { name = "PaperSurface" };` then `_surface.Create()` and `_artCamera.targetTexture = _surface; _artCamera.aspect = 1f; _artCamera.orthographicSize = _designSize.y / 2f;`.
- **OnDestroy:** `_surface.Release(); Object.Destroy(_surface);`.
- **No update logic** — the camera renders every frame automatically because `targetTexture` is set.
- **Important:** `_artCamera`'s `orthographicSize` and `aspect` are set once and never touched again. The RT contents are deterministic.

#### `ArtInputBridge : MonoBehaviour, IArtInputBridge` *(Input)*
Lives on the same UI Canvas as the paper `RawImage`.
```csharp
// inspector fields:
//   RawImage _paperImage              (the on-screen paper)
//   RectTransform _paperRect          (== _paperImage.rectTransform)
//   Camera _uiCamera                  (Canvas event camera)
//   IPaperRig _rig                    (injected via VContainer + IInjectable, or resolved in Start)

public bool TryScreenToArtWorld(Vector2 screenPos, out Vector2 artWorldPos) {
    if (!RectTransformUtility.ScreenPointToLocalPointInRectangle(
            _paperRect, screenPos, _uiCamera, out var local)) {
        artWorldPos = default; return false;
    }
    var rect = _paperRect.rect;
    var uv = new Vector2(
        (local.x - rect.xMin) / rect.width,
        (local.y - rect.yMin) / rect.height);
    if (uv.x < 0 || uv.x > 1 || uv.y < 0 || uv.y > 1) {
        artWorldPos = default; return false;
    }
    artWorldPos = _rig.ArtCamera.ViewportToWorldPoint(uv);
    return true;
}
```
- Returns `false` when the toddler tapped outside the RawImage (HUD button area, backdrop, off-screen).
- Used by every feature that does world-space picking — `Coloring`, `ShapeBuilder`, and any future feature like stickers.

#### `PaperRigModule : MonoBehaviour, IServiceModule` *(Installers)*
Scene-scoped installer. Dragged onto `ColorBookLifetimeScope._installers[]`.
```csharp
// inspector fields:
//   PaperRig _rig
//   ArtInputBridge _bridge

public void Register(IContainerBuilder builder) {
    builder.RegisterInstance<IPaperRig>(_rig);
    builder.RegisterInstance<IArtInputBridge>(_bridge);
}
```
- Registers as `Instance` because both are MonoBehaviours already in the scene.
- Lifetime is implicitly tied to the scene (Unity destroys them on unload).

---

### 32.6 Feature — `Coloring`

#### `ColoringStateRepository` *(Repository)*
In-memory model. Owns "currently selected color" and the palette in use.
```csharp
public sealed class ColoringStateRepository {
    public IColorPalette Palette { get; private set; }
    public int SelectedIndex { get; private set; }
    public Color CurrentColor => Palette.Colors[SelectedIndex];
    public event Action<int> SelectedIndexChanged;
    public void SetPalette(IColorPalette palette);   // resets SelectedIndex to 0
    public void SelectColor(int index);
}
```
- **Why a repository:** presenter and controller both need to read/write current color; an event-emitting POCO is simpler than wiring two signals.

#### `ColoringController` *(Systems)* — implements `IColoringController`
Builds and pushes `PaintRegionCommand` instances; spawns `ColorRegionView` per region.
```csharp
// fields: IUndoStack _undo, ColoringStateRepository _state, ColorRegionFactory _factory, IEventBus _bus
public interface IColoringController {
    UniTask SpawnRegionsAsync(IDrawingTemplate template);
    void PaintRegion(ColorRegionView view);          // builds command, pushes to undo stack
    void Clear();
}
// sub: ShapeAssembledSignal (via flow controller, not direct)
// pub: ColorAppliedSignal (via PaintRegionCommand)
```

#### `ColorRegionView : MonoBehaviour` *(Views)*
Sprite + `PolygonCollider2D`, on `Artwork` layer. Tapped via `Physics2D.OverlapPoint` from `ColoringInputBinder`.
```csharp
public sealed class ColorRegionView : MonoBehaviour {
    public string RegionId { get; }
    public Color Color { get; }                      // current paint
    public void Initialize(ColorRegionDTO dto);
    public void SetColor(Color c);                   // setter only; no logic
}
```

#### `ColoringInputBinder` *(Systems)* — `IStartable, IDisposable`
Subscribes to `IInputReader.PointerDown`. On each tap:
1. `_bridge.TryScreenToArtWorld(screenPos, out var artPos)` — bail if outside the paper.
2. `Physics2D.OverlapPoint(artPos, _artworkMask)` against the `Artwork` layer.
3. If hit, `ColoringController.PaintRegion(hit.GetComponent<ColorRegionView>())`.

```csharp
// fields: IInputReader _input, IArtInputBridge _bridge, IColoringController _coloring, LayerMask _artworkMask
```
Note: `_bridge` is the same instance the entire scene uses — no per-feature coordinate math.

#### `PaintRegionCommand` *(Commands)*
Source in section 23. Holds `view`, `fromColor`, `toColor`, `bus`. Symmetrical execute/undo.

#### `ColorPaletteView`, `ColorPalettePresenter` *(UI)*
Sources in section 25. Presenter binds `ColoringStateRepository.SelectedIndexChanged` ↔ `IColorPaletteView`.

#### `ColorRegionFactory` *(Systems)*
Mirror of `ShapePieceFactory` for regions. Pool-friendly.

---

### 32.7 Feature — `History`

#### `HistoryController` *(Systems)* — `IStartable, IDisposable`
Owns the per-session `IUndoStack` (registered scoped, so a new ColorBook scene = new stack).
```csharp
// fields: IUndoStack _stack, IEventBus _bus
public sealed class HistoryController : IStartable, IDisposable {
    public bool CanUndo => _stack.CanUndo;
    public bool CanRedo => _stack.CanRedo;
    public event Action StateChanged;
    public void Undo();                              // _stack.Undo() + StateChanged
    public void Redo();
    // sub: DrawingSelectedSignal → _stack.Clear()
}
```

#### `HistoryButtonsView : MonoBehaviour` *(UI)*
Two big arrow buttons. Setters only.
```csharp
public interface IHistoryButtonsView {
    event Action UndoClicked;
    event Action RedoClicked;
    void SetUndoEnabled(bool enabled);
    void SetRedoEnabled(bool enabled);
}
```

#### `HistoryPresenter` *(UI)*
Wires controller `StateChanged` ↔ view enable/disable; view click events → controller.

---

### 32.8 Feature — `Capture`

#### `CaptureController` *(Systems)*
The orchestrator behind the "Capture" button. Stateless other than guarding against concurrent captures.
```csharp
// fields: ICaptureService _capture, IGalleryService _gallery, IEventBus _bus
public sealed class CaptureController {
    public bool IsCapturing { get; }
    public UniTask<SavedArtworkDTO> CaptureCurrentAsync(string templateId);
}
// pub: ArtworkCapturedSignal (mid-flow), ArtworkSavedSignal (post-save)
```
- **Flow:** `_capture.CaptureAsync()` → `_gallery.SaveAsync(bytes, templateId)` → publish signals.
- **Concurrency:** sets `IsCapturing = true` on entry; UI binds button enabled to `!IsCapturing` to prevent double-tap.
- **No camera or sprite args** — capture reads `IPaperRig.Surface` directly inside the service.

#### `CaptureButtonPresenter` *(UI)*
Wires button click → `CaptureController.CaptureCurrentAsync`. Disables button while in progress. Shows toast on `ArtworkSavedSignal`.

---

### 32.9 Feature — `Progression`

#### `ProgressionService` *(Systems)* — implements `IProgressionService`
The only place that knows what "completed" means.
- **Persistence:** delegates to `IPersistenceService` under key `"progression"`.
- **Load order:** `AppBoot` calls `LoadAsync()` early.
- **Save trigger:** after `MarkCompleted`, debounced 500 ms to coalesce a burst of "Next" presses.

#### `ProgressionRepository` *(Repository)*
Pure in-memory holder used by the service. Separated so tests can inspect state without going through file IO.

---

### 32.10 Feature — `ColorBookFlow`

#### `ColorBookFlowController` *(Systems)* — `IStartable, IDisposable`
**The only orchestrator inside the ColorBook scene.** Drives the panel FSM: `Catalog → Building → Coloring → Done`.
```csharp
// fields:
//   IEventBus _bus
//   IDrawingTemplateCatalog _catalog
//   ShapeBuilderController _builder
//   IColoringController _coloring
//   CaptureController _capture
//   IProgressionService _progression
//   ColorBookSceneRefs _refs        (panel roots to enable/disable)
//   Fsm<ColorBookState> _fsm
```
- **State table:**

  | State      | On enter                                       | Triggers exit                  |
  |------------|-----------------------------------------------|--------------------------------|
  | `Catalog`  | Show catalog panel                            | `DrawingSelectedSignal`        |
  | `Building` | `_builder.BuildAsync(id)`                     | `ShapeAssembledSignal`         |
  | `Coloring` | `_coloring.SpawnRegionsAsync(template)`       | "Next" or "Capture" pressed    |
  | `Done`     | Run autosave capture, mark completed, `Go(Catalog)` for next | always advances        |

- **"Next" sequence:** `_capture.CaptureCurrentAsync` → `_progression.MarkCompleted` → `_catalog.Release(current)` → `_catalog.LoadAsync(_catalog.NextUnseen(current))` → re-enter `Building`.

---

### 32.11 Feature — `ArtBook`

#### `GalleryPresenter` *(UI)* — `IAsyncStartable, IDisposable`
Lists artworks, opens fullscreen view, deletes, shares.
```csharp
// fields: IGalleryService _gallery, IGalleryView _view, IExternalShareService _share, IEventBus _bus
```
- **Start:** `_gallery.ListAsync()` → `_view.SetItems(...)`.
- **Subscribes** to `ArtworkSavedSignal` to live-refresh if the user pops back in.

#### `IGalleryView` *(UI)*
```csharp
public interface IGalleryView {
    event Action<string> OnArtworkTapped;
    event Action<string> OnDeleteRequested;
    event Action<string> OnShareRequested;
    void SetItems(IReadOnlyList<GalleryItemVM> items);
    void ShowFullscreen(Texture2D full);
    void HideFullscreen();
}
```

#### `IExternalShareService` *(Core)*
Platform plugin shim (iOS Photos / Android MediaStore).
```csharp
public interface IExternalShareService {
    UniTask SaveToCameraRollAsync(byte[] png);
    UniTask ShareAsync(byte[] png, string subject);
}
```

---

### 32.12 App Layer

#### `AppBoot` *(App/Boot)* — `IAsyncStartable`
Single entry point. Steps in section 29.
```csharp
// fields: IAssetProviderService _assets, IPersistenceService _persist, IProgressionService _progress,
//         IAudioService _audio, ISceneService _scenes, BootConfig _cfg
public sealed class AppBoot : IAsyncStartable {
    public UniTask StartAsync(CancellationToken ct);
}
```

#### LifetimeScopes
- `RootLifetimeScope` — section 21. Registers all services + `IEventBus`. Persists for app lifetime.
- `MainMenuLifetimeScope` — registers `MainMenuPresenter` and view.
- `ColorBookLifetimeScope` — section 21. Registers feature installers + `ColorBookFlowController` as entry point.
- `ArtBookLifetimeScope` — registers `GalleryPresenter` + view + `IExternalShareService`.

All scope classes are thin: serialized fields for scene refs, `Configure(IContainerBuilder)` only.

---

### 32.13 Cross-cutting types

#### `ColorBookSceneRefs : MonoBehaviour` *(App)*
Aggregates all scene-bound Unity references that features need: `Camera artCamera`, `Transform catalogRoot`, `Transform builderRoot`, `Transform coloringRoot`, `RectTransform hudRoot`, `ColorPaletteView paletteView`, `HistoryButtonsView historyView`. Registered as a singleton in `ColorBookLifetimeScope` so features don't `Find` things.

#### `IInstaller` *(App)*
```csharp
public interface IInstaller { void Install(IContainerBuilder builder); }
```
Implemented as `ScriptableObject` per feature so scopes can drag them in the inspector (section 22).

---

### 32.14 Class summary table

| Class | Layer | Role | Key dependencies |
|---|---|---|---|
| `AppBoot` | App | Startup sequencer | assets, persist, progression, scenes |
| `RootLifetimeScope` | App | Root DI | configs |
| `ColorBookLifetimeScope` | App | Scene DI | scene refs, installers |
| `DrawingCatalogController` | Feature | Grid logic | catalog, bus |
| `DrawingCatalogPresenter` | Feature | UI bridge | view, controller, catalog |
| `ShapeBuilderController` | Feature | Piece spawn + snap tracking | catalog, factory, bus, cfg |
| `ShapePieceView` | Feature | Draggable piece MB | input, audio |
| `ColoringStateRepository` | Feature | Current color model | — |
| `ColoringController` | Feature | Region spawn + paint cmd | undo, state, factory, bus |
| `ColorRegionView` | Feature | Region sprite MB | — |
| `PaintRegionCommand` | Feature | Undoable paint | view, bus |
| `PaperRig` | Feature | RT + ArtCamera owner | — |
| `ArtInputBridge` | Feature | Screen→art-world picking | rig, raw image, ui cam |
| `PaperRigModule` | Feature | DI registration | rig, bridge |
| `HistoryController` | Feature | Undo/redo facade | undo stack, bus |
| `CaptureController` | Feature | Capture+save orchestration | capture svc, gallery, bus |
| `ColorBookFlowController` | Feature | Scene FSM | bus, catalog, builder, coloring, capture, progression |
| `GalleryPresenter` | Feature | Art book listing | gallery, share, view, bus |
| `BoundedUndoStack` | Lib | Capped undo store | — |
| `EventBus` | Lib | Pub/sub | — |
| `Fsm<TState>` | Lib | Generic FSM | — |
| `AddressableAssetProviderService` | Service | Addressables wrapper | — |
| `FileGalleryService` | Service | Gallery file IO | paths, thumb gen, bus |
| `RenderTextureCaptureService` | Service | PNG render from rig.Surface | paper rig |
| `JsonPersistenceService` | Service | Settings/progression IO | — |
| `SceneService` | Service | Async scene loads | — |
| `AudioService` | Service | SFX playback | assets |
| `ProgressionService` | Service | Completion tracking | persistence |

If you add a class not in this table, add it here in the same PR. This table is the cheap mental-model index — keep it honest.