tabletopkit

# TabletopKit

Create multiplayer spatial board games on a virtual table surface using
TabletopKit. Handles game layout, equipment interaction, player seating, turn
management, state synchronization, and RealityKit rendering. **visionOS 2.0+
only.** Targets Swift 6.3.

## Contents

- [Setup](#setup)
- [Game Configuration](#game-configuration)
- [Table and Board](#table-and-board)
- [Equipment (Pieces, Cards, Dice)](#equipment-pieces-cards-dice)
- [Player Seats](#player-seats)
- [Game Actions and Turns](#game-actions-and-turns)
- [Interactions](#interactions)
- [RealityKit Rendering](#realitykit-rendering)
- [Group Activities Integration](#group-activities-integration)
- [Common Mistakes](#common-mistakes)
- [Review Checklist](#review-checklist)
- [References](#references)

## Setup

### Platform Requirement

TabletopKit is exclusive to visionOS. It requires visionOS 2.0+. Multiplayer
features using Group Activities require visionOS 2.0+ devices on a FaceTime
call. The Simulator supports single-player layout testing but not multiplayer.

### Project Configuration

1. `import TabletopKit` in source files that define game logic.
2. `import RealityKit` for entity-based rendering.
3. For multiplayer, add the **Group Activities** capability in Signing &
   Capabilities.
4. Provide 3D assets (USDZ) in a RealityKit content bundle for tables, pieces,
   cards, and dice.

### Key Types Overview

| Type | Role |
|---|---|
| `TabletopGame` | Central game manager; owns setup, actions, observers, rendering |
| `TableSetup` | Configuration object passed to `TabletopGame` init |
| `Tabletop` / `EntityTabletop` | Protocol for the table surface |
| `Equipment` / `EntityEquipment` | Protocol for interactive game pieces |
| `TableSeat` / `EntityTableSeat` | Protocol for player seat positions |
| `TabletopAction` | Commands that modify game state |
| `TabletopInteraction` | Gesture-driven player interactions with equipment |
| `TabletopGame.Observer` | Callback protocol for reacting to confirmed actions |
| `TabletopGame.RenderDelegate` | Callback protocol for visual updates |
| `EntityRenderDelegate` | RealityKit-specific render delegate |

## Game Configuration

Build a game in three steps: define the table, configure the setup, create the
`TabletopGame` instance.

```swift
import TabletopKit
import RealityKit

let table = GameTable()
var setup = TableSetup(tabletop: table)
setup.add(seat: PlayerSeat(index: 0, pose: seatPose0))
setup.add(seat: PlayerSeat(index: 1, pose: seatPose1))
setup.add(equipment: GamePawn(id: .init(1)))
setup.add(equipment: GameDie(id: .init(2)))
setup.register(action: MyCustomAction.self)

let game = TabletopGame(tableSetup: setup)
game.claimAnySeat()
```

Call `update(deltaTime:)` each frame if automatic updates are not enabled via
the `.tabletopGame(_:parent:automaticUpdate:)` modifier. Read state safely with
`withCurrentSnapshot(_:)`.

## Table and Board

### Tabletop Protocol

Conform to `EntityTabletop` to define the playing surface. Provide a `shape`
(round or rectangular) and a RealityKit `Entity` for visual representation.

```swift
struct GameTable: EntityTabletop {
    var shape: TabletopShape
    var entity: Entity
    var id: EquipmentIdentifier

    init() {
        entity = try! Entity.load(named: "table/game_table", in: contentBundle)
        shape = .round(entity: entity)
        id = .init(0)
    }
}
```

### Table Shapes

Use factory methods on `TabletopShape`:

```swift
// Round table from dimensions
let round = TabletopShape.round(
    center: .init(x: 0, y: 0, z: 0),
    radius: 0.5,
    thickness: 0.05,
    in: .meters
)

// Rectangular table from entity
let rect = TabletopShape.rectangular(entity: tableEntity)
```

## Equipment (Pieces, Cards, Dice)

### Equipment Protocol

All interactive game objects conform to `Equipment` (or `EntityEquipment` for
RealityKit-rendered pieces). Each piece has an `id` (`EquipmentIdentifier`) and
an `initialState` property.

Choose the state type based on the equipment:

| State Type | Use Case |
|---|---|
| `BaseEquipmentState` | Generic pieces, pawns, tokens |
| `CardState` | Playing cards (tracks `faceUp` / face-down) |
| `DieState` | Dice with an integer `value` |
| `RawValueState` | Custom data encoded as `UInt64` |

### Defining Equipment

```swift
// Pawn -- uses BaseEquipmentState
struct GamePawn: EntityEquipment {
    var id: EquipmentIdentifier
    var initialState: BaseEquipmentState
    var entity: Entity

    init(id: EquipmentIdentifier) {
        self.id = id
        self.entity = try! Entity.load(named: "pieces/pawn", in: contentBundle)
        self.initialState = BaseEquipmentState(
            parentID: .init(0), seatControl: .any,
            pose: .identity, entity: entity
        )
    }
}

// Card -- uses CardState (tracks faceUp)
struct PlayingCard: EntityEquipment {
    var id: EquipmentIdentifier
    var initialState: CardState
    var entity: Entity

    init(id: EquipmentIdentifier) {
        self.id = id
        self.entity = try! Entity.load(named: "cards/card", in: contentBundle)
        self.initialState = .faceDown(
            parentID: .init(0), seatControl: .any,
            pose: .identity, entity: entity
        )
    }
}

// Die -- uses DieState (tracks integer value)
struct GameDie: EntityEquipment {
    var id: EquipmentIdentifier
    var initialState: DieState
    var entity: Entity

    init(id: EquipmentIdentifier) {
        self.id = id
        self.entity = try! Entity.load(named: "dice/d6", in: contentBundle)
        self.initialState = DieState(
            value: 1, parentID: .init(0), seatControl: .any,
            pose: .identity, entity: entity
        )
    }
}
```

### ControllingSeats

Restrict which players can interact with a piece via `seatControl`:
- `.any` -- any player
- `.restricted([seatID1, seatID2])` -- specific seats only
- `.current` -- only the seat whose turn it is
- `.inherited` -- inherits from parent equipment

### Equipment Hierarchy and Layout

Equipment