# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Project Overview

A hockey match engine simulation built with PhaserJS and TypeScript. The engine uses continuous positioning (exact X/Y coordinates on a 2D rink) combined with behavior trees for AI decision-making to create a realistic hockey match simulation.

**Core Concept**: Players have exact positions on a 60x30m international hockey rink, with AI running behavior trees at 60 FPS to make tactical decisions (passing, shooting, positioning, etc.).

## Development Commands

```bash
# Start development server (runs on port 3000)
pnpm run dev

# Build for production
pnpm run build

# Preview production build
pnpm run preview
```

## Coordinate System

**Critical**: The rink uses a centered coordinate system:
- Origin (0, 0) = center of rink
- Rink dimensions: 60m length × 30m width
- Left goal: x = -26m, Right goal: x = +26m
- All positions use **meters as floats** (not integers)
- Screen rendering: 1 meter = 20 pixels (SCALE constant)

## Architecture

### Project Structure

```
src/
  config/
    constants.ts      # All game constants (rink dimensions, colors, speeds, AI parameters)
  game/
    main.ts          # Phaser game initialization and config
    GameScene.ts     # Main game scene (rendering, game loop, physics, event handling)
    Goal.ts          # Goal structure with physics bodies and scoring detection
  entities/
    Player.ts        # Player entity with physics, movement, and detection systems
    Puck.ts          # Puck entity with physics and state management
  systems/
    BehaviorTree.ts      # Main behavior tree system for AI decision-making
    BehaviorNodes.ts     # Base classes (Selector, Sequence, Condition, Action)
    behaviors/
      SkaterBehavior.ts           # Top-level skater AI (context selector)
      GoalieBehavior.ts           # Goalie-specific AI
      TransitionBehavior.ts       # Loose puck / neutral zone behavior
      offensive/
        PuckCarrierBehavior.ts    # Shoot/carry/evade decisions
        OffensiveSupportBehavior.ts  # Support when teammate has puck (planned)
      defensive/
        DefensiveBehavior.ts      # Chase and pressure opponent
  types/
    game.ts          # TypeScript types and interfaces
  utils/
    coordinates.ts   # Game ↔ screen coordinate conversion
    math.ts          # Distance, angle utilities
```

### Implementation Status

**✓ Completed Phases:**
- **Phase 1**: Environment setup, rink rendering
- **Phase 2**: Player entities with smooth acceleration/deceleration and rotation
- **Phase 3**: Puck physics and possession mechanics
- **Phase 4**: Puck carrier behavior (shoot/carry/evade)
- **Phase 6**: Basic defensive behavior (chase puck carrier)
- **Phase 7**: Basic goalie AI (track puck position)
- **Phase 8**: Goal detection, scoring system, pause-aware reset timers

**🚧 In Progress / Partial:**
- **Phase 5**: Offensive support (placeholder only)
- Tackle mechanics (implemented but needs tuning)
- Puck reception (implemented with skill-based probability)

**📋 Planned:**
- Passing AI (identify and execute passes)
- Advanced offensive positioning (heat maps, formations)
- Faceoffs and game flow states
- Save mechanics for goalies

---

## Core Systems Documentation

### 1. Behavior Tree System

**Location:** [src/systems/BehaviorTree.ts](src/systems/BehaviorTree.ts), [src/systems/BehaviorNodes.ts](src/systems/BehaviorNodes.ts)

**Purpose:** AI decision-making engine that runs at 60 FPS for each player.

**Architecture:**
- **BehaviorNode**: Abstract base class for all nodes
- **Selector**: OR logic - tries children until one succeeds
- **Sequence**: AND logic - all children must succeed
- **Condition**: Boolean predicate functions
- **Action**: Leaf nodes that return PlayerAction

**Decision Tree Structure:**
```
Root Selector
├─ Goalie? → GoalieBehavior
└─ Skater? → SkaterBehavior
    ├─ Has puck? → PuckCarrierBehavior (shoot/carry/evade)
    ├─ Teammate has puck? → OffensiveSupportBehavior (planned)
    ├─ Opponent has puck? → DefensiveBehavior (chase)
    └─ Loose puck → TransitionBehavior (chase loose puck)
```

**Key Files:**
- [BehaviorTree.ts:26-60](src/systems/BehaviorTree.ts#L26-L60): Main tree evaluation
- [SkaterBehavior.ts:21-39](src/systems/behaviors/SkaterBehavior.ts#L21-L39): Context-based selector

---

### 2. Player Entity System

**Location:** [src/entities/Player.ts](src/entities/Player.ts)

**Purpose:** Player physics, movement, rotation, and nearby player detection.

**Key Features:**

**Movement System** ([Player.ts:186-286](src/entities/Player.ts#L186-L286)):
- Smooth acceleration with ease-out curve (PLAYER_ACCELERATION)
- Speed-dependent rotation (faster = wider turns)
- Deceleration when near target or after goals
- Stop threshold to prevent jittering (MOVEMENT_STOP_THRESHOLD)

**Player Detection System** ([Player.ts:324-387](src/entities/Player.ts#L324-L387)):
- Physics-based circular sensor (NEAR_PLAYER_DETECTION_RADIUS = 4m)
- Field-of-view filtering (NEAR_PLAYER_DETECTION_ANGLE = 180°)
- Maintains sets: `nearbyPlayers`, `nearbyOpponents`, `nearbyTeammates`
- Methods: `getDetectedOpponents()`, `getDetectedTeammates()`

**Tackle System** ([Player.ts:290-312](src/entities/Player.ts#L290-L312)):
- Cooldown timer (TACKLE_COOLDOWN = 1000ms)
- Fall duration when tackled (TACKLE_FALL_DURATION = 500ms)
- Speed requirement (TACKLE_MIN_SPEED = 2 m/s)
- Angle-based effectiveness modifiers

**Player Attributes** ([types/game.ts:27-33](src/types/game.ts#L27-L33)):
- `speed`: Movement speed (0-100) → m/s via SPEED_SCALE_FACTOR
- `skill`: Pass/shot accuracy, decision quality
- `tackling`: Tackle success probability
- `balance`: Resist being tackled
- `handling`: Puck reception and control

---

### 3. Puck Entity System

**Location:** [src/entities/Puck.ts](src/entities/Puck.ts)

**Purpose:** Puck physics, state management, and possession tracking.

**Puck States** ([types/game.ts:22](src/types/game.ts#L22)):
- `loose`: Free on ice, physics-driven
- `carried`: Held by player (carrier ID tracked)
- `passing`: In flight between players (future)
- `shot`: Shot toward goal

**Physics Configuration** ([Puck.ts:36-56](src/entities/Puck.ts#L36-L56)):
- Circular collision body (PUCK_RADIUS = 0.2m)
- Max velocity: MAX_PUCK_VELOCITY = 50 m/s
- Drag (ice friction): PUCK_DRAG = 200 pixels/s²
- Bounce coefficient: PUCK_BOUNCE = 0.6 (loses energy)
- World bounds collision enabled

**Key Methods:**
- `setCarrier(playerId, team)`: Assign possession
- `setLoose()`: Release to physics simulation
- `update()`: Sync game coordinates with physics body

---

### 4. Puck Carrier Behavior

**Location:** [src/systems/behaviors/offensive/PuckCarrierBehavior.ts](src/systems/behaviors/offensive/PuckCarrierBehavior.ts)

**Purpose:** Tactical decisions when player has possession.

**Decision Priority:**
1. **Evade** if opponent threatens head-on ([PuckCarrierBehavior.ts:104-254](src/systems/behaviors/offensive/PuckCarrierBehavior.ts#L104-L254))
2. **Shoot** if good opportunity ([PuckCarrierBehavior.ts:262-308](src/systems/behaviors/offensive/PuckCarrierBehavior.ts#L262-L308))
3. **Carry** toward opponent's net (default)

**Evasion System:**
- Uses physics-based player detection (NEAR_PLAYER_DETECTION_RADIUS)
- Checks if opponent is within 60° of goal direction
- Maintains consistent evasion direction per opponent (stored in `activeEvasions` map)
- Evasion angle: ±60° (EVASION_ANGLE) from goal direction
- Clears evasion when opponent leaves detection zone

**Shooting Logic:**
- Must be in front of goal (not behind)
- Distance ≤ SHOOTING_RANGE (10m)
- Angle-based accuracy:
  - Close range (≤3m): 120° shooting angle allowed
  - Normal range: 60° shooting angle required
- Aims at center of net (targetY = 0)

**Debug Visualization** (when DEBUG = true):
- Green line to goal
- Red circle around threats being evaded
- Yellow arrow showing evasion direction
- Orange circles for detected opponents

---

### 5. GameScene System

**Location:** [src/game/GameScene.ts](src/game/GameScene.ts)

**Purpose:** Main game loop, physics management, collision detection, event handling.

**Key Responsibilities:**

**Physics Setup:**
- Player-player collisions (including tackle mechanics)
- Player-puck overlaps (pickup and reception)
- Puck-goal post collisions with bounce
- Detection sensor overlaps (nearby player tracking)

**Puck Management:**
- Carrier positioning: puck stays 1m in front of carrier
- Pickup radius: PUCK_PICKUP_RADIUS = 1.5m
- Reception skill checks (PUCK_RECEPTION_BASE_CHANCE)
- Speed-based reception difficulty

**Shooting System:**
- Shot speed: SHOT_SPEED = 30 m/s (or 0.6× for close range)
- Post bounce: reduces speed and adds random angle variation
- Goal detection via overlap with scoring zone

**Tackle System:**
- Cooldown enforcement (TACKLE_COOLDOWN)
- Angle-based effectiveness (head-on = 100%, side = 70%, etc.)
- Closing speed modifiers
- Puck loose probability (TACKLE_PUCK_LOOSE_CHANCE = 60%)

**Goal System:**
- Freeze game on goal event
- 3-second pause-aware timer
- Player deceleration (GOAL_DECELERATION_RATE)
- Reset positions to center ice

---

### 6. Coordinate System

**Location:** [src/utils/coordinates.ts](src/utils/coordinates.ts)

**Purpose:** Convert between game coordinates (meters) and screen coordinates (pixels).

**Critical Details:**
- **Game coordinates:** Origin (0, 0) at center of rink, meters as floats
- **Screen coordinates:** Origin at top-left, pixels
- **Scale factor:** 1 meter = 20 pixels (SCALE constant)
- **Y-axis inversion:** Game Y increases upward, screen Y increases downward

**Key Methods:**
- `gameToScreen(scene, gameX, gameY)`: Meters → pixels
- `screenToGame(scene, screenX, screenY)`: Pixels → meters
- `getScreenCenter(scene)`: Canvas center in pixels

**Rink Layout:**
- Rink: 60m × 30m
- Left goal: x = -26m (GOAL_LINE_OFFSET)
- Right goal: x = +26m
- Blue lines: x = ±9m (BLUE_LINE_OFFSET)
- Center ice: (0, 0)

---

### 7. Constants Configuration

**Location:** [src/config/constants.ts](src/config/constants.ts)

**Purpose:** Centralized configuration for all game parameters.

**Categories:**

**Game Settings:**
- DEBUG, FPS, UI_BOTTOM_PADDING

**Rink Dimensions:**
- RINK_LENGTH, RINK_WIDTH, SCALE, corner radius, zone lines

**Player Constants:**
- Radius (goalie vs skater), rotation speed, acceleration/deceleration
- Speed scale factor, movement threshold

**Puck Constants:**
- Radius, pickup range, carry distance, max velocity
- Drag, bounce, shot speed, reception parameters

**AI/Behavior:**
- Shooting range and angle thresholds (normal vs close-range)
- Goalie range, detection radius and angle
- Evasion angle

**Tackle Mechanics:**
- Success modifiers, cooldown, fall duration
- Angle thresholds and modifiers
- Closing speed thresholds

**Collision/Physics:**
- Post bounce reduction, puck loose chance
- Reception skill scaling

---

## Type Definitions

**Location:** [src/types/game.ts](src/types/game.ts)

**Key Types:**

```typescript
PlayerPosition: 'LW' | 'C' | 'RW' | 'LD' | 'RD' | 'G'
TeamSide: 'home' | 'away'
PlayerState: 'offensive' | 'defensive'
PuckState: 'loose' | 'carried' | 'passing' | 'shot'

PlayerAttributes: {
  speed, skill, tackling, balance, handling
}

GameState: {
  puck: Puck
  allPlayers: Player[]
}

PlayerAction: {
  type: 'move' | 'chase_puck' | 'skate_with_puck' | 'shoot' | 'idle'
  targetX?, targetY?
}
```

---

## Technical Stack

- **Framework**: Phaser 3.90.0 (Arcade Physics engine)
- **TypeScript**: Strict mode enabled
- **Build Tool**: Vite 5.4
- **Target FPS**: 60 (configured in constants.ts)
- **Physics**: Arcade physics with zero gravity (top-down view)
- **Coordinate System**: Centered origin (0,0), meters as float values
- **Rendering Scale**: 1 meter = 20 pixels

---

## Debug Features

**Toggle:** Set `DEBUG = true` in [constants.ts](src/config/constants.ts)

**Visual Overlays:**
- **Player movement:** Line and marker showing target position
- **Player detection:** Magenta wedge showing field-of-view sensor
- **Puck carrier evasion:**
  - Green line to goal
  - Red circles around detected threats
  - Yellow/green arrows showing evasion direction
  - Orange circles for all nearby opponents

**Console Logging:**
- Goal events with team and goal location
- Shot attempts with player ID
- Tackle results and success calculations

---

## Development Workflow

**Hot Reload Development:**
```bash
pnpm run dev  # Starts on localhost:3000 with hot reload
```

**Testing Approach:**
- Test each subsystem incrementally before integration
- Use DEBUG mode to visualize AI decision-making
- Tune constants based on gameplay feel (see [constants.ts](src/config/constants.ts))
- Validate physics with edge cases (goal posts, rink boundaries)

**Key Tuning Parameters:**
- Player acceleration/deceleration curves → smooth movement feel
- Detection radius/angle → evasion responsiveness
- Shooting angles → goal frequency balance
- Tackle modifiers → physical gameplay intensity
- Puck drag/bounce → realistic puck physics

**Documentation:**
- **[PLAN.md](PLAN.md)**: Phase-by-phase implementation plan
- **[NOTES.md](NOTES.md)**: Architecture decisions and design rationale
- **[REVIEW.md](REVIEW.md)**: Progress reviews and lessons learned
- **[CLAUDE.md](CLAUDE.md)** (this file): System reference for AI assistant

---

## Implementation Patterns

**Adding New Behaviors:**
1. Create behavior class extending `BehaviorNode` in `src/systems/behaviors/`
2. Implement `tick(player, gameState)` method
3. Add to appropriate selector in `SkaterBehavior` or `GoalieBehavior`
4. Test in isolation before integration

**Adding New Constants:**
1. Add to appropriate section in [constants.ts](src/config/constants.ts)
2. Use semantic names (e.g., `SHOOTING_RANGE` not `MAX_DIST`)
3. Include units in comments (meters, m/s, radians, pixels)
4. Export for use across codebase

**Physics Bodies:**
- Players: Circular bodies (radius varies by position)
- Puck: Circular body with drag and bounce
- Goals: Static rectangular bodies for posts/bars
- Sensors: Physics zones with `overlap` not `collide`

**Coordinate Conversions:**
- Always use `CoordinateUtils.gameToScreen()` and `screenToGame()`
- Never mix coordinate systems in calculations
- Store positions in game coordinates (meters), convert for rendering