Expo Game Support

A complete game-development library for Expo/React Native that adds advanced physics, a robust game loop, and optimized touch input handling.

🚀 Features

• Physics Engine: Gravity, collisions, forces, impulses, sleeping
• Optimized Game Loop: Fixed or variable time step, FPS control
• Advanced Touch Input: Optimized gestures (tap, swipe, long press, double tap)
• Collision Detection: AABB and circle with basic resolution
• Collision Events: Collision start/end and trigger enter/exit callbacks
• Rendering (optional): WebGL renderer via Expo GL (GLRenderer) and typed render interfaces (IRenderer, TextureInfo, DrawOptions)
• Assets & Audio: AssetManager for images/spritesheets/textures and audio (via expo-asset/expo-av); SpriteAnimator for sprite animations
• 2D Math: Comprehensive vector operations
• TypeScript: Fully typed for an improved DX

📦 Installation

npm install expo-game-support

Required peer dependencies:

npm install expo react react-native \
  expo-asset expo-av expo-gl \
  react-native-gesture-handler react-native-reanimated

🎮 Basic Usage

Initial setup (Web)

import { GameEngine, GameObject, Vector2D } from 'expo-game-support';

// Configure the game engine
const gameEngine = new GameEngine({
  width: 400,
  height: 600,
  gravity: new Vector2D(0, 981), // Gravity pointing down
  gameLoop: {
    targetFPS: 60,
    maxDeltaTime: 0.05,
    enableFixedTimeStep: true
  }
});

// Initialize and start
gameEngine.initialize();
gameEngine.start();

Setup for React Native/Expo

import React, { useEffect, useRef } from 'react';
import { View, PanResponder } from 'react-native';
import { GameEngine, GameObject, Vector2D } from 'expo-game-support';

export default function GameComponent() {
  const gameEngineRef = useRef<GameEngine | null>(null);

  useEffect(() => {
    const gameEngine = new GameEngine({
      width: 400,
      height: 600,
      gravity: new Vector2D(0, 981),
      gameLoop: {
        targetFPS: 60,
        maxDeltaTime: 0.016,
        enableFixedTimeStep: true
      }
    });

    gameEngineRef.current = gameEngine;
    gameEngine.initialize();
    gameEngine.start();

    return () => gameEngine.stop();
  }, []);

  // Wire PanResponder to touch input
  const panResponder = PanResponder.create({
    onStartShouldSetPanResponder: () => true,
    onMoveShouldSetPanResponder: () => true,
    onPanResponderGrant: (evt) => {
      gameEngineRef.current?.handleTouchStart(evt.nativeEvent);
    },
    onPanResponderMove: (evt) => {
      gameEngineRef.current?.handleTouchMove(evt.nativeEvent);
    },
    onPanResponderRelease: (evt) => {
      gameEngineRef.current?.handleTouchEnd(evt.nativeEvent);
    },
  });

  return (
    <View style={{ flex: 1 }} {...panResponder.panHandlers}>
      {/* Your game UI here */}
    </View>
  );
}

Create game objects

// Create a ball with physics
const ball = new GameObject({
  id: 'ball',
  position: new Vector2D(200, 100),
  size: new Vector2D(40, 40),
  physics: {
    mass: 1,
    velocity: new Vector2D(0, 0),
    acceleration: new Vector2D(0, 0),
    friction: 0.1,
    restitution: 0.8, // Bounciness
    isStatic: false
  }
});

// Add to the engine
gameEngine.addGameObject(ball);

Handle touch input

// Touch events
gameEngine.onTouch('player-input', (touchEvent) => {
  if (touchEvent.type === 'start') {
    console.log('Touch started at:', touchEvent.position);
  }
});

// Gestures
gameEngine.onGesture('player-gestures', (gesture) => {
  switch (gesture.type) {
    case 'tap':
      console.log('Tap at:', gesture.position);
      break;
    case 'swipe':
      console.log('Swipe direction:', gesture.direction);
      break;
  }
});

Update loop

gameEngine.onUpdate((deltaTime) => {
  // Game logic per frame
  const ball = gameEngine.getGameObject('ball');
  if (ball) {
    // Apply forces, check conditions, etc.
  }
});

gameEngine.onRender((interpolation) => {
  // Rendering (hook into your renderer of choice)
});

🖼️ Rendering with GLRenderer (Expo GL)

This library ships an optional WebGL renderer built on top of expo-gl. You can use the typed interfaces exported from render/IRenderer and the concrete GLRenderer:

import { GameEngine } from 'expo-game-support';
import { GLView } from 'expo-gl';
import { GLRenderer } from 'expo-game-support';

export default function GameWithGL() {
  return (
    <GLView
      style={{ flex: 1 }}
      onContextCreate={(gl) => {
        const renderer = new GLRenderer(gl);

        const engine = new GameEngine({
          width: gl.drawingBufferWidth,
          height: gl.drawingBufferHeight,
          gameLoop: { targetFPS: 60, maxDeltaTime: 0.033, enableFixedTimeStep: true },
        });

        // Hook engine render to the renderer
        engine.onRender(() => {
          renderer.beginFrame();
          // renderer.drawRect({...}) or draw your textures/sprites here
          renderer.endFrame();
          gl.endFrameEXP?.();
        });

        engine.initialize();
        engine.start();
      }}
    />
  );
}

Types you can import:

import type { IRenderer, TextureInfo, DrawOptions, Rect as RenderRect } from 'expo-game-support';

📤 Exports Overview

From expo-game-support root entry:

• Core: GameEngine, GameLoop, GameObject
• Physics: PhysicsEngine, CollisionDetector
• Input: TouchInputManager (web), TouchInputManagerRN (React Native)
• Utils: BoundaryChecker, ObjectCleaner, ScoreZone, ScoreManager, ObjectSpawner
• Assets: AssetManager, SpriteAnimator
• Rendering (optional): GLRenderer and render types IRenderer, TextureInfo, DrawOptions, Rect as RenderRect
• Types: GameEngineConfig, GameObjectConfig, PhysicsBody, GameTouchEvent, GameLoopConfig, CollisionEvent, and assets types like AssetManifest, AssetId, ImageAsset, TextureAsset, SoundAsset, LoadedTexture, LoadedSpriteSheet, SoundHandle

Check src/index.ts for the authoritative export list.

🧭 Platform Notes

• Web-only helpers:

  • uploadTextureFromImage(image: HTMLImageElement | ImageBitmap) is intended for web contexts using DOM-compatible image sources.
  • On iOS/Android, you must decode the asset to raw RGBA pixels before calling gl.texImage2D (see uploadTextureFromAssetNative placeholder). Consider integrating native-assisted decoding or use Expo utilities to obtain a pixel buffer.

• React Native setup:

  • Ensure you have react-native-gesture-handler and react-native-reanimated properly configured per their docs.
  • For expo-gl, use GLView and call gl.endFrameEXP() after each frame.
  • Prefer platform-specific files when needed (e.g. *.web.ts vs *.native.ts) to separate implementations.

• Tree-shaking:

  • The API is designed to be modular. Import only what you use to keep bundle sizes small.

🎯 Advanced Examples

Simple Pong

import { GameEngine, GameObject, Vector2D } from 'expo-game-support';

class PongGame {
  private gameEngine: GameEngine;
  private ball: GameObject;
  private paddle: GameObject;

  constructor() {
    this.gameEngine = new GameEngine({
      width: 400,
      height: 600,
      gravity: new Vector2D(0, 0), // No gravity for Pong
      gameLoop: {
        targetFPS: 60,
        maxDeltaTime: 0.016,
        enableFixedTimeStep: true
      }
    });

    this.setupGame();
  }

  private setupGame() {
    // Crear pelota
    this.ball = new GameObject({
      id: 'ball',
      position: new Vector2D(200, 300),
      size: new Vector2D(20, 20),
      physics: {
        mass: 1,
        velocity: new Vector2D(200, 150),
        acceleration: new Vector2D(0, 0),
        friction: 0,
        restitution: 1,
        isStatic: false
      }
    });

    // Crear paddle
    this.paddle = new GameObject({
      id: 'paddle',
      position: new Vector2D(200, 550),
      size: new Vector2D(80, 20),
      physics: {
        mass: 10,
        velocity: new Vector2D(0, 0),
        acceleration: new Vector2D(0, 0),
        friction: 0.9,
        restitution: 0,
        isStatic: false
      }
    });

    this.gameEngine.addGameObject(this.ball);
    this.gameEngine.addGameObject(this.paddle);

    // Handle input to move the paddle
    this.gameEngine.onTouch('paddle-control', (touch) => {
      if (touch.type === 'move') {
        this.paddle.position.x = touch.position.x;
      }
    });

    // Game logic
    this.gameEngine.onUpdate((deltaTime) => {
      this.updateGame(deltaTime);
    });
  }

  private updateGame(deltaTime: number) {
    // Wall bounces
    if (this.ball.position.x <= 10 || this.ball.position.x >= 390) {
      this.ball.physics!.velocity.x *= -1;
    }
    if (this.ball.position.y <= 10) {
      this.ball.physics!.velocity.y *= -1;
    }

    // Reset if the ball leaves screen bottom
    if (this.ball.position.y > 610) {
      this.resetBall();
    }
  }

  private resetBall() {
    this.ball.position = new Vector2D(200, 300);
    this.ball.physics!.velocity = new Vector2D(200, 150);
  }

  start() {
    this.gameEngine.initialize();
    this.gameEngine.start();
  }
}

Particle System

class ParticleSystem {
  private gameEngine: GameEngine;
  private particles: GameObject[] = [];

  constructor(gameEngine: GameEngine) {
    this.gameEngine = gameEngine;
  }

  createExplosion(position: Vector2D, particleCount: number = 20) {
    for (let i = 0; i < particleCount; i++) {
      const angle = (Math.PI * 2 * i) / particleCount;
      const speed = 100 + Math.random() * 200;
      
      const particle = new GameObject({
        id: `particle_${Date.now()}_${i}`,
        position: position.clone(),
        size: new Vector2D(4, 4),
        physics: {
          mass: 0.1,
          velocity: new Vector2D(
            Math.cos(angle) * speed,
            Math.sin(angle) * speed
          ),
          acceleration: new Vector2D(0, 0),
          friction: 0.02,
          restitution: 0.3,
          isStatic: false
        }
      });

      this.particles.push(particle);
      this.gameEngine.addGameObject(particle);

      // Destroy particle after 3 seconds
      setTimeout(() => {
        particle.destroy();
        this.particles = this.particles.filter(p => p !== particle);
      }, 3000);
    }
  }
}

📚 API Reference

GameEngine

Constructor

new GameEngine(config: GameEngineConfig)

Main methods

• initialize(): Initialize engine
• start(): Start game
• pause(): Pause game
• resume(): Resume game
• stop(): Stop game

Object management

• addGameObject(gameObject: GameObject): Add an object
• removeGameObject(id: string): Remove an object
• getGameObject(id: string): Get by ID
• getAllGameObjects(): Get all objects

Callbacks

• onUpdate(callback: (deltaTime: number) => void): Update callback
• onRender(callback: (interpolation: number) => void): Render callback
• onTouch(id: string, callback: (event: TouchEvent) => void): Touch callback
• onGesture(id: string, callback: (gesture: GestureEvent) => void): Gesture callback
• onCollisionStart(cb), onCollisionEnd(cb): Physics collision events
• onTriggerEnter(cb), onTriggerExit(cb): Trigger events

GameObject

Constructor

new GameObject(config: GameObjectConfig)

Properties

• id: string: Unique identifier
• position: Vector2D: World position
• size: Vector2D: Object size
• rotation: number: Radians
• physics?: PhysicsBody: Optional rigid body

Methods

• update(deltaTime: number): Per-frame update
• applyForce(force: Vector2D): Apply force
• applyImpulse(impulse: Vector2D): Apply impulse
• containsPoint(point: Vector2D): Point test
• destroy(): Destroy object

Vector2D

Constructor

new Vector2D(x: number = 0, y: number = 0)

Operations

• add(vector: Vector2D)
• subtract(vector: Vector2D)
• multiply(scalar: number)
• divide(scalar: number)
• magnitude()
• normalize()
• dot(vector: Vector2D)
• distance(vector: Vector2D)

🔧 Advanced Configuration

Performance optimization

// Configure for performance
const gameEngine = new GameEngine({
  width: 400,
  height: 600,
  gravity: new Vector2D(0, 981),
  gameLoop: {
    targetFPS: 30, // Reduce FPS on slower devices
    maxDeltaTime: 0.033, // Limit time jumps
    enableFixedTimeStep: false // Variable timestep for performance
  }
});

// Touch input config
gameEngine.touchInputManager.updateConfig({
  deadZone: 10, // Larger dead zone
  maxTouchPoints: 2, // Limit touch points
  touchSensitivity: 0.8 // Lower sensitivity
});

🤝 Contributing

1. Fork the repository
2. Create a feature branch (git checkout -b feature/AmazingFeature)
3. Commit your changes (git commit -m 'Add some AmazingFeature')
4. Push the branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

📄 License

MIT License - see LICENSE for details.

🙏 Acknowledgements

• Inspired by engines like Phaser and Matter.js
• Tuned specifically for the Expo/React Native ecosystem

Note: To minimize tunneling and improve stability, we recommend a fixed time step (enableFixedTimeStep: true) with targetFPS 60 for physics-heavy scenes. Collision and trigger events are available via GameEngine.onCollisionStart/End and onTriggerEnter/Exit.