src/components/CoinType.js

@@ -0,0 +1,39 @@
+/**
+ * CoinType component - defines coin value and type
+ */
+export class CoinType {
+  /**
+   * @param {string} type - Type of coin: 'gold', 'silver', 'diamond', 'health'
+   */
+  constructor(type = 'gold') {
+    /** @type {string} Coin type */
+    this.type = type;
+    
+    /** @type {number} Score value */
+    this.scoreValue = this.getScoreValue(type);
+    
+    /** @type {number} Health restore amount (0 for non-health coins) */
+    this.healthRestore = type === 'health' ? 10 : 0;
+  }
+
+  /**
+   * Get score value based on coin type
+   * @param {string} type - Coin type
+   * @returns {number} Score value
+   */
+  getScoreValue(type) {
+    switch (type) {
+      case 'diamond':
+        return 50;
+      case 'gold':
+        return 10;
+      case 'silver':
+        return 5;
+      case 'health':
+        return 0; // Health coins don't give score
+      default:
+        return 10;
+    }
+  }
+}
+

src/components/ObstacleType.js

@@ -0,0 +1,25 @@
+/**
+ * ObstacleType component - defines obstacle behavior type
+ */
+export class ObstacleType {
+  /**
+   * @param {string} type - Type of obstacle: 'normal', 'fast', 'chasing', 'spinning'
+   */
+  constructor(type = 'normal') {
+    /** @type {string} Obstacle type */
+    this.type = type;
+    
+    /** @type {number} Speed multiplier (1.0 = normal) */
+    this.speedMultiplier = type === 'fast' ? 1.5 : 1.0;
+    
+    /** @type {boolean} Whether this obstacle chases the player */
+    this.chases = type === 'chasing';
+    
+    /** @type {boolean} Whether this obstacle spins */
+    this.spins = type === 'spinning';
+    
+    /** @type {number} Rotation speed multiplier */
+    this.rotationSpeed = type === 'spinning' ? 3.0 : 1.0;
+  }
+}
+

src/components/ParticleEmitter.js

@@ -0,0 +1,28 @@
+/**
+ * ParticleEmitter component - emits particles for visual effects
+ */
+export class ParticleEmitter {
+  /**
+   * @param {number} count - Number of particles to emit
+   * @param {number} lifetime - Lifetime of particles in seconds
+   * @param {number} color - Particle color (hex)
+   * @param {number} [speed=5] - Particle speed
+   */
+  constructor(count, lifetime, color, speed = 5) {
+    /** @type {number} Number of particles */
+    this.count = count;
+    
+    /** @type {number} Lifetime in seconds */
+    this.lifetime = lifetime;
+    
+    /** @type {number} Particle color */
+    this.color = color;
+    
+    /** @type {number} Particle speed */
+    this.speed = speed;
+    
+    /** @type {boolean} Whether emitter is active */
+    this.active = true;
+  }
+}
+

src/components/PowerUp.js

@@ -0,0 +1,42 @@
+/**
+ * PowerUp component - defines power-up type and duration
+ */
+export class PowerUp {
+  /**
+   * @param {string} type - Type of power-up: 'speed', 'shield', 'multiplier', 'magnet'
+   * @param {number} [duration=10] - Duration in seconds
+   */
+  constructor(type, duration = 10) {
+    /** @type {string} Power-up type */
+    this.type = type;
+    
+    /** @type {number} Duration in seconds */
+    this.duration = duration;
+    
+    /** @type {number} Time remaining */
+    this.timeRemaining = duration;
+    
+    /** @type {boolean} Whether power-up is active */
+    this.active = true;
+  }
+
+  /**
+   * Update power-up timer
+   * @param {number} deltaTime - Time since last frame in seconds
+   * @returns {boolean} True if still active
+   */
+  update(deltaTime) {
+    if (!this.active) return false;
+    
+    this.timeRemaining -= deltaTime;
+    
+    if (this.timeRemaining <= 0) {
+      this.active = false;
+      this.timeRemaining = 0;
+      return false;
+    }
+    
+    return true;
+  }
+}
+

src/game/EntityFactory.js

@@ -4,6 +4,9 @@ import { MeshComponent } from '../components/MeshComponent.js';
 import { Collidable } from '../components/Collidable.js';
 import { Health } from '../components/Health.js';
 import { Invincibility } from '../components/Invincibility.js';
+import { ObstacleType } from '../components/ObstacleType.js';
+import { CoinType } from '../components/CoinType.js';
+import { PowerUp } from '../components/PowerUp.js';
 import { PlayerTag, CoinTag, ObstacleTag, BoundaryConstrained } from '../components/Tags.js';
 import { GameConfig } from './GameConfig.js';
 
@@ -65,19 +68,58 @@ export class EntityFactory {
   /**
    * Create a collectible coin entity
    * @param {number} [index=0] - Unique index for animation offset
+   * @param {string} [type] - Optional coin type ('gold', 'silver', 'diamond', 'health')
    * @returns {EntityId} The coin entity ID
    */
-  createCoin(index = 0) {
+  createCoin(index = 0, type = null) {
     const entity = this.world.createEntity();
 
-    // Create mesh
-    const geometry = new window.THREE.SphereGeometry(0.3, 16, 16);
+    // Determine coin type (weighted random if not specified)
+    let coinType = type;
+    if (!coinType) {
+      const rand = Math.random();
+      if (rand < 0.6) {
+        coinType = 'gold'; // 60% gold
+      } else if (rand < 0.85) {
+        coinType = 'silver'; // 25% silver
+      } else if (rand < 0.95) {
+        coinType = 'diamond'; // 10% diamond
+      } else {
+        coinType = 'health'; // 5% health
+      }
+    }
+
+    const typeComponent = new CoinType(coinType);
+
+    // Create mesh with different colors/sizes based on type
+    let size = 0.3;
+    let color = 0xFFD700; // Gold
+    let emissive = 0xFFD700;
+    let emissiveIntensity = 0.3;
+
+    if (coinType === 'silver') {
+      color = 0xC0C0C0;
+      emissive = 0xC0C0C0;
+      size = 0.25;
+    } else if (coinType === 'diamond') {
+      color = 0x00FFFF;
+      emissive = 0x00FFFF;
+      emissiveIntensity = 0.6;
+      size = 0.4;
+    } else if (coinType === 'health') {
+      color = 0x00FF00;
+      emissive = 0x00FF00;
+      emissiveIntensity = 0.4;
+      size = 0.35;
+    }
+
+    const geometry = new window.THREE.SphereGeometry(size, 16, 16);
     const material = new window.THREE.MeshStandardMaterial({
-      color: 0xFFD700,
+      color: color,
       metalness: 0.8,
       roughness: 0.2,
-      emissive: 0xFFD700,
-      emissiveIntensity: 0.3
+      emissive: emissive,
+      emissiveIntensity: emissiveIntensity
     });
     const mesh = new window.THREE.Mesh(geometry, material);
     mesh.castShadow = true;
@@ -92,6 +134,7 @@ export class EntityFactory {
     this.world.addComponent(entity, new Transform(x, 0.5, z));
     this.world.addComponent(entity, new MeshComponent(mesh));
     this.world.addComponent(entity, new Collidable(0.8, 'coin'));
+    this.world.addComponent(entity, typeComponent);
     this.world.addComponent(entity, new CoinTag(index));
 
     return entity;
@@ -99,15 +142,42 @@ export class EntityFactory {
 
   /**
    * Create an obstacle entity
+   * @param {string} [type] - Optional obstacle type ('normal', 'fast', 'chasing', 'spinning')
    * @returns {EntityId} The obstacle entity ID
    */
-  createObstacle() {
+  createObstacle(type = null) {
     const entity = this.world.createEntity();
 
-    // Create mesh
+    // Determine obstacle type (weighted random if not specified)
+    let obstacleType = type;
+    if (!obstacleType) {
+      const rand = Math.random();
+      if (rand < 0.5) {
+        obstacleType = 'normal';
+      } else if (rand < 0.7) {
+        obstacleType = 'fast';
+      } else if (rand < 0.85) {
+        obstacleType = 'chasing';
+      } else {
+        obstacleType = 'spinning';
+      }
+    }
+
+    const typeComponent = new ObstacleType(obstacleType);
+
+    // Create mesh with different colors based on type
     const geometry = new window.THREE.BoxGeometry(1.5, 2, 1.5);
+    let color = 0xFF4500; // Default orange-red
+    if (obstacleType === 'fast') {
+      color = 0xFF0000; // Red
+    } else if (obstacleType === 'chasing') {
+      color = 0x8B0000; // Dark red
+    } else if (obstacleType === 'spinning') {
+      color = 0xFF6347; // Tomato
+    }
+
     const material = new window.THREE.MeshStandardMaterial({
-      color: 0xFF4500,
+      color: color,
       metalness: 0.3,
       roughness: 0.7
     });
@@ -123,11 +193,12 @@ export class EntityFactory {
       posZ = (Math.random() - 0.5) * (this.groundSize - 4);
     } while (Math.abs(posX) < 3 && Math.abs(posZ) < 3);
 
-    // Random velocity
+    // Base velocity (will be modified by ObstacleSystem for different types)
+    const baseSpeed = 0.05;
     const velocity = new Velocity(
-      (Math.random() - 0.5) * 0.05,
+      (Math.random() - 0.5) * baseSpeed * typeComponent.speedMultiplier,
       0,
-      (Math.random() - 0.5) * 0.05
+      (Math.random() - 0.5) * baseSpeed * typeComponent.speedMultiplier
     );
 
     // Add components
@@ -135,12 +206,89 @@ export class EntityFactory {
     this.world.addComponent(entity, velocity);
     this.world.addComponent(entity, new MeshComponent(mesh));
     this.world.addComponent(entity, new Collidable(1.5, 'obstacle'));
+    this.world.addComponent(entity, typeComponent);
     this.world.addComponent(entity, new ObstacleTag());
     this.world.addComponent(entity, new BoundaryConstrained(this.groundSize));
 
     return entity;
   }
 
+  /**
+   * Create a power-up entity
+   * @param {string} [type] - Optional power-up type ('speed', 'shield', 'multiplier', 'magnet')
+   * @returns {EntityId} The power-up entity ID
+   */
+  createPowerUp(type = null) {
+    const entity = this.world.createEntity();
+
+    // Determine power-up type (random if not specified)
+    let powerUpType = type;
+    if (!powerUpType) {
+      const rand = Math.random();
+      if (rand < 0.25) {
+        powerUpType = 'speed';
+      } else if (rand < 0.5) {
+        powerUpType = 'shield';
+      } else if (rand < 0.75) {
+        powerUpType = 'multiplier';
+      } else {
+        powerUpType = 'magnet';
+      }
+    }
+
+    // Get duration based on type
+    let duration = 10;
+    let color = 0x00FF00;
+    let size = 0.4;
+
+    switch (powerUpType) {
+      case 'speed':
+        duration = GameConfig.POWERUP_DURATION_SPEED;
+        color = 0x00FFFF; // Cyan
+        break;
+      case 'shield':
+        duration = GameConfig.POWERUP_DURATION_SHIELD;
+        color = 0x0000FF; // Blue
+        break;
+      case 'multiplier':
+        duration = GameConfig.POWERUP_DURATION_MULTIPLIER;
+        color = 0xFF00FF; // Magenta
+        break;
+      case 'magnet':
+        duration = GameConfig.POWERUP_DURATION_MAGNET;
+        color = 0xFFFF00; // Yellow
+        break;
+    }
+
+    const powerUpComponent = new PowerUp(powerUpType, duration);
+
+    // Create mesh
+    const geometry = new window.THREE.OctahedronGeometry(size, 0);
+    const material = new window.THREE.MeshStandardMaterial({
+      color: color,
+      metalness: 0.9,
+      roughness: 0.1,
+      emissive: color,
+      emissiveIntensity: 0.5
+    });
+    const mesh = new window.THREE.Mesh(geometry, material);
+    mesh.castShadow = true;
+    mesh.receiveShadow = true;
+    this.scene.add(mesh);
+
+    // Random position
+    const x = (Math.random() - 0.5) * (this.groundSize - 4);
+    const z = (Math.random() - 0.5) * (this.groundSize - 4);
+
+    // Add components
+    this.world.addComponent(entity, new Transform(x, 1, z));
+    this.world.addComponent(entity, new MeshComponent(mesh));
+    this.world.addComponent(entity, new Collidable(0.6, 'powerup'));
+    this.world.addComponent(entity, powerUpComponent);
+
+    return entity;
+  }
+
   /**
    * Remove entity and its mesh from scene
    * @param {EntityId} entityId - The entity to destroy

src/game/Game.js

@@ -11,12 +11,16 @@ import { CoinSystem } from '../systems/CoinSystem.js';
 import { ObstacleSystem } from '../systems/ObstacleSystem.js';
 import { CollisionSystem } from '../systems/CollisionSystem.js';
 import { InvincibilitySystem } from '../systems/InvincibilitySystem.js';
+import { ParticleSystem } from '../systems/ParticleSystem.js';
+import { PowerUpSystem } from '../systems/PowerUpSystem.js';
 import { RenderSystem } from '../systems/RenderSystem.js';
 
 // Components
 import { Transform } from '../components/Transform.js';
 import { Health } from '../components/Health.js';
 import { Invincibility } from '../components/Invincibility.js';
+import { CoinType } from '../components/CoinType.js';
+import { PowerUp } from '../components/PowerUp.js';
 
 /**
  * Main Game class - manages the game loop and coordinates all systems.
@@ -47,6 +51,9 @@ export class Game {
     /** @type {EntityId[]} Array of obstacle entity IDs */
     this.obstacles = [];
     
+    /** @type {EntityId[]} Array of power-up entity IDs */
+    this.powerUps = [];
+
     /** @type {number} Last frame timestamp for deltaTime calculation */
     this.lastTime = performance.now();
     
@@ -89,6 +96,23 @@ export class Game {
     /** @type {number} Time since last health regeneration */
     this.healthRegenTimer = 0;
 
+    // Screen shake state
+    /** @type {number} Remaining screen shake time */
+    this.screenShakeTime = 0;
+    
+    /** @type {import('three').Vector3} Original camera position offset */
+    this.cameraBaseOffset = new window.THREE.Vector3(0, 10, 15);
+
+    // Difficulty scaling state
+    /** @type {number} Game start time */
+    this.gameStartTime = performance.now() / 1000;
+    
+    /** @type {number} Last score when obstacle was added */
+    this.lastDifficultyScore = 0;
+    
+    /** @type {number} Last time when obstacle was added */
+    this.lastDifficultyTime = 0;
+
     this.init();
     this.setupEventListeners();
     this.animate();
@@ -186,13 +210,17 @@ export class Game {
     this.inputSystem = new InputSystem();
     this.world.addSystem(this.inputSystem);
 
-    // Player control
-    this.world.addSystem(new PlayerControlSystem(this.inputSystem));
+    // Player control (will set power-up system after it's created)
+    this.playerControlSystem = new PlayerControlSystem(this.inputSystem);
+    this.world.addSystem(this.playerControlSystem);
 
     // Movement and physics
     this.world.addSystem(new MovementSystem());
     this.world.addSystem(new BoundarySystem());
-    this.world.addSystem(new ObstacleSystem());
+    
+    // Obstacle system (will set player entity after player is created)
+    this.obstacleSystem = new ObstacleSystem();
+    this.world.addSystem(this.obstacleSystem);
 
     // Game-specific behavior
     this.world.addSystem(new CoinSystem());
@@ -200,6 +228,19 @@ export class Game {
     // Invincibility system (before collision to update state)
     this.world.addSystem(new InvincibilitySystem());
 
+    // Particle system
+    this.particleSystem = new ParticleSystem(this.scene);
+    this.world.addSystem(this.particleSystem);
+
+    // Power-up system (will set player entity after player is created)
+    this.powerUpSystem = new PowerUpSystem();
+    this.world.addSystem(this.powerUpSystem);
+    
+    // Connect power-up system to player control system
+    if (this.playerControlSystem) {
+      this.playerControlSystem.setPowerUpSystem(this.powerUpSystem);
+    }
+
     // Collision detection
     this.collisionSystem = new CollisionSystem();
     this.collisionSystem.onCollision((entity1, entity2, layer1, layer2) => {
@@ -215,13 +256,21 @@ export class Game {
     // Create player
     this.playerEntity = this.entityFactory.createPlayer();
     
+    // Set player entity in systems that need it
+    if (this.obstacleSystem) {
+      this.obstacleSystem.setPlayerEntity(this.playerEntity);
+    }
+    if (this.powerUpSystem) {
+      this.powerUpSystem.setPlayerEntity(this.playerEntity);
+    }
+
     // Create coins
     for (let i = 0; i < GameConfig.INITIAL_COIN_COUNT; i++) {
       const coin = this.entityFactory.createCoin(this.coins.length);
       this.coins.push(coin);
     }
 
-    // Create obstacles
+    // Create obstacles (mix of types)
     for (let i = 0; i < GameConfig.INITIAL_OBSTACLE_COUNT; i++) {
       const obstacle = this.entityFactory.createObstacle();
       this.obstacles.push(obstacle);
@@ -237,6 +286,12 @@ export class Game {
       this.collectCoin(coinEntity);
     }
 
+    // Player-PowerUp collision
+    if ((layer1 === 'player' && layer2 === 'powerup') || (layer1 === 'powerup' && layer2 === 'player')) {
+      const powerUpEntity = layer1 === 'powerup' ? entity1 : entity2;
+      this.collectPowerUp(powerUpEntity);
+    }
+
     // Player-Obstacle collision
     if ((layer1 === 'player' && layer2 === 'obstacle') || (layer1 === 'obstacle' && layer2 === 'player')) {
       const playerEntity = layer1 === 'player' ? entity1 : entity2;
@@ -246,6 +301,11 @@ export class Game {
   }
 
   collectCoin(coinEntity) {
+    // Get coin position and type before destroying
+    const coinTransform = this.world.getComponent(coinEntity, Transform);
+    const coinType = this.world.getComponent(coinEntity, CoinType);
+    const coinPosition = coinTransform ? coinTransform.position.clone() : null;
+
     // Remove coin
     this.entityFactory.destroyEntity(coinEntity);
     const index = this.coins.indexOf(coinEntity);
@@ -253,7 +313,42 @@ export class Game {
       this.coins.splice(index, 1);
     }
 
-    // Update combo system
+    // Determine particle color based on coin type
+    let particleColor = 0xFFD700; // Default gold
+    if (coinType) {
+      if (coinType.type === 'silver') {
+        particleColor = 0xC0C0C0;
+      } else if (coinType.type === 'diamond') {
+        particleColor = 0x00FFFF;
+      } else if (coinType.type === 'health') {
+        particleColor = 0x00FF00;
+      }
+    }
+
+    // Emit particles for coin collection
+    if (coinPosition && this.particleSystem) {
+      this.particleSystem.emit(
+        coinPosition,
+        GameConfig.PARTICLE_COUNT_COIN,
+        particleColor,
+        8
+      );
+    }
+
+    // Handle health coin
+    if (coinType && coinType.type === 'health') {
+      const health = this.world.getComponent(this.playerEntity, Health);
+      if (health) {
+        health.heal(coinType.healthRestore);
+        this.updateUI();
+      }
+      // Health coins don't contribute to combo or score
+      const newCoin = this.entityFactory.createCoin(this.coins.length);
+      this.coins.push(newCoin);
+      return;
+    }
+
+    // Update combo system (only for score coins)
     const currentTime = performance.now() / 1000; // Convert to seconds
     const timeSinceLastCoin = currentTime - this.lastCoinTime;
 
@@ -272,9 +367,10 @@ export class Game {
 
     this.lastCoinTime = currentTime;
 
-    // Calculate score with combo multiplier
-    const baseScore = GameConfig.COMBO_BASE_SCORE;
-    const scoreGain = baseScore * this.comboMultiplier;
+    // Calculate score with combo multiplier and power-up multiplier (use coin's base value)
+    const baseScore = coinType ? coinType.scoreValue : GameConfig.COMBO_BASE_SCORE;
+    const powerUpMultiplier = this.powerUpSystem ? this.powerUpSystem.scoreMultiplier : 1.0;
+    const scoreGain = baseScore * this.comboMultiplier * powerUpMultiplier;
     this.score += scoreGain;
 
     // Check for new high score
@@ -285,12 +381,85 @@ export class Game {
 
     this.updateUI();
 
-    // Spawn new coin
-    const newCoin = this.entityFactory.createCoin(this.coins.length);
-    this.coins.push(newCoin);
+    // Spawn new coin or power-up (based on chance)
+    if (Math.random() < GameConfig.POWERUP_SPAWN_CHANCE) {
+      const powerUp = this.entityFactory.createPowerUp();
+      this.powerUps.push(powerUp);
+    } else {
+      const newCoin = this.entityFactory.createCoin(this.coins.length);
+      this.coins.push(newCoin);
+    }
+  }
+
+  collectPowerUp(powerUpEntity) {
+    // Get power-up position and type before destroying
+    const powerUpTransform = this.world.getComponent(powerUpEntity, Transform);
+    const powerUp = this.world.getComponent(powerUpEntity, PowerUp);
+    const powerUpPosition = powerUpTransform ? powerUpTransform.position.clone() : null;
+
+    // Remove power-up
+    this.entityFactory.destroyEntity(powerUpEntity);
+    const index = this.powerUps.indexOf(powerUpEntity);
+    if (index > -1) {
+      this.powerUps.splice(index, 1);
+    }
+
+    // Activate power-up effect
+    if (powerUp && this.powerUpSystem) {
+      this.powerUpSystem.activatePowerUp(powerUp.type, powerUp.duration);
+      
+      // Special handling for shield - activate invincibility
+      if (powerUp.type === 'shield') {
+        const invincibility = this.world.getComponent(this.playerEntity, Invincibility);
+        if (invincibility) {
+          invincibility.activate(powerUp.duration);
+        }
+      }
+    }
+
+    // Emit particles
+    if (powerUpPosition && this.particleSystem) {
+      let particleColor = 0x00FF00;
+      if (powerUp) {
+        switch (powerUp.type) {
+          case 'speed':
+            particleColor = 0x00FFFF;
+            break;
+          case 'shield':
+            particleColor = 0x0000FF;
+            break;
+          case 'multiplier':
+            particleColor = 0xFF00FF;
+            break;
+          case 'magnet':
+            particleColor = 0xFFFF00;
+            break;
+        }
+      }
+      this.particleSystem.emit(
+        powerUpPosition,
+        GameConfig.PARTICLE_COUNT_COIN,
+        particleColor,
+        10
+      );
+    }
+
+    // Spawn new coin or power-up
+    if (Math.random() < GameConfig.POWERUP_SPAWN_CHANCE) {
+      const newPowerUp = this.entityFactory.createPowerUp();
+      this.powerUps.push(newPowerUp);
+    } else {
+      const newCoin = this.entityFactory.createCoin(this.coins.length);
+      this.coins.push(newCoin);
+    }
   }
 
   handleObstacleCollision(playerEntity, obstacleEntity) {
+    // Check if player has shield power-up active
+    if (this.powerUpSystem && this.powerUpSystem.isActive('shield')) {
+      return; // No damage if shield is active
+    }
+
     // Check if player is invincible
     const invincibility = this.world.getComponent(playerEntity, Invincibility);
     if (invincibility && invincibility.getIsInvincible()) {
@@ -309,6 +478,19 @@ export class Game {
       invincibility.activate(GameConfig.INVINCIBILITY_DURATION);
     }
 
+    // Screen shake on damage
+    this.screenShakeTime = GameConfig.SCREEN_SHAKE_DURATION;
+
+    // Emit damage particles
+    if (this.particleSystem && playerTransform) {
+      this.particleSystem.emit(
+        playerTransform.position.clone().add(new window.THREE.Vector3(0, 0.5, 0)),
+        GameConfig.PARTICLE_COUNT_DAMAGE,
+        0xFF0000, // Red color
+        6
+      );
+    }
+
     // Push player back
     const pushDirection = playerTransform.position.clone().sub(obstacleTransform.position);
     pushDirection.y = 0;
@@ -332,8 +514,20 @@ export class Game {
 
     const playerTransform = this.world.getComponent(this.playerEntity, Transform);
     if (playerTransform) {
-      this.camera.position.x = playerTransform.position.x;
-      this.camera.position.z = playerTransform.position.z + 15;
+      // Base camera position
+      let cameraX = playerTransform.position.x;
+      let cameraZ = playerTransform.position.z + 15;
+      let cameraY = 10;
+
+      // Apply screen shake
+      if (this.screenShakeTime > 0) {
+        const intensity = (this.screenShakeTime / GameConfig.SCREEN_SHAKE_DURATION) * GameConfig.SCREEN_SHAKE_INTENSITY;
+        cameraX += (Math.random() - 0.5) * intensity;
+        cameraY += (Math.random() - 0.5) * intensity;
+        cameraZ += (Math.random() - 0.5) * intensity;
+      }
+
+      this.camera.position.set(cameraX, cameraY, cameraZ);
       this.camera.lookAt(playerTransform.position);
     }
   }
@@ -383,12 +577,14 @@ export class Game {
     // Clean up old entities
     [...this.coins].forEach(coin => this.entityFactory.destroyEntity(coin));
     [...this.obstacles].forEach(obstacle => this.entityFactory.destroyEntity(obstacle));
+    [...this.powerUps].forEach(powerUp => this.entityFactory.destroyEntity(powerUp));
     if (this.playerEntity) {
       this.entityFactory.destroyEntity(this.playerEntity);
     }
 
     this.coins = [];
     this.obstacles = [];
+    this.powerUps = [];
 
     // Reset game state
     this.score = 0;
@@ -403,6 +599,14 @@ export class Game {
     // Reset health regeneration timer
     this.healthRegenTimer = 0;
     
+    // Reset screen shake
+    this.screenShakeTime = 0;
+    
+    // Reset difficulty scaling
+    this.gameStartTime = performance.now() / 1000;
+    this.lastDifficultyScore = 0;
+    this.lastDifficultyTime = 0;
+
     // Recreate entities
     this.createGameEntities();
 
@@ -531,6 +735,33 @@ export class Game {
       });
   }
 
+  /**
+   * Update difficulty scaling - spawn more obstacles over time
+   * @param {number} deltaTime - Time since last frame in seconds
+   */
+  updateDifficulty(deltaTime) {
+    const currentTime = performance.now() / 1000;
+    const elapsedTime = currentTime - this.gameStartTime;
+
+    // Check if we should add an obstacle based on score
+    const scoreDiff = this.score - this.lastDifficultyScore;
+    if (scoreDiff >= GameConfig.DIFFICULTY_SCORE_INTERVAL && 
+        this.obstacles.length < GameConfig.MAX_OBSTACLES) {
+      const newObstacle = this.entityFactory.createObstacle();
+      this.obstacles.push(newObstacle);
+      this.lastDifficultyScore = this.score;
+    }
+
+    // Check if we should add an obstacle based on time
+    const timeDiff = currentTime - this.lastDifficultyTime;
+    if (timeDiff >= GameConfig.DIFFICULTY_TIME_INTERVAL && 
+        this.obstacles.length < GameConfig.MAX_OBSTACLES) {
+      const newObstacle = this.entityFactory.createObstacle();
+      this.obstacles.push(newObstacle);
+      this.lastDifficultyTime = currentTime;
+    }
+  }
+
   /**
    * Load high score from localStorage
    * @returns {number} High score value
@@ -602,6 +833,11 @@ export class Game {
     }
 
     if (this.gameActive) {
+      // Update screen shake
+      if (this.screenShakeTime > 0) {
+        this.screenShakeTime = Math.max(0, this.screenShakeTime - deltaTime);
+      }
+
       // Update combo timer
       this.comboTimer = Math.max(0, this.comboTimer - deltaTime);
       if (this.comboTimer <= 0 && this.comboMultiplier > 1) {
@@ -620,6 +856,9 @@ export class Game {
         this.healthRegenTimer = 0;
       }
 
+      // Difficulty scaling - add obstacles over time
+      this.updateDifficulty(deltaTime);
+
       // Update ECS world with actual deltaTime
       this.world.update(deltaTime);
 

src/game/GameConfig.js

@@ -18,9 +18,31 @@ export const GameConfig = {
   INVINCIBILITY_DURATION: 1.5, // Seconds of invincibility after damage
   INVINCIBILITY_FLASH_RATE: 0.1, // Seconds between flash toggles
   
+  // Screen Shake
+  SCREEN_SHAKE_DURATION: 0.3, // Seconds of screen shake after damage
+  SCREEN_SHAKE_INTENSITY: 0.5, // Camera shake intensity
+  
+  // Particle Effects
+  PARTICLE_COUNT_COIN: 20, // Particles when collecting coin
+  PARTICLE_COUNT_DAMAGE: 15, // Particles when taking damage
+  PARTICLE_LIFETIME: 1.0, // Seconds particles live
+  
+  // Power-Ups
+  POWERUP_SPAWN_CHANCE: 0.3, // Chance to spawn power-up instead of coin (30%)
+  POWERUP_DURATION_SPEED: 10, // Speed boost duration
+  POWERUP_DURATION_SHIELD: 15, // Shield duration
+  POWERUP_DURATION_MULTIPLIER: 20, // Score multiplier duration
+  POWERUP_DURATION_MAGNET: 15, // Magnet duration
+  POWERUP_SPEED_MULTIPLIER: 1.5, // Speed boost multiplier
+  POWERUP_SCORE_MULTIPLIER: 2.0, // Score multiplier value
+  POWERUP_MAGNET_RANGE: 5.0, // Magnet attraction range
+  
   // Difficulty
   INITIAL_OBSTACLE_COUNT: 8,
   INITIAL_COIN_COUNT: 10,
+  DIFFICULTY_SCORE_INTERVAL: 100, // Add obstacle every N points
+  DIFFICULTY_TIME_INTERVAL: 30, // Add obstacle every N seconds
+  MAX_OBSTACLES: 20, // Maximum obstacles on screen
   
   // Arena
   GROUND_SIZE: 30,

src/systems/ObstacleSystem.js

@@ -2,18 +2,67 @@ import { System } from '../ecs/System.js';
 import { ObstacleTag, BoundaryConstrained } from '../components/Tags.js';
 import { Transform } from '../components/Transform.js';
 import { Velocity } from '../components/Velocity.js';
+import { ObstacleType } from '../components/ObstacleType.js';
+import { MeshComponent } from '../components/MeshComponent.js';
+import { PlayerTag } from '../components/Tags.js';
 
 /**
  * ObstacleSystem - handles obstacle-specific behavior
  */
 export class ObstacleSystem extends System {
-  update(_deltaTime) {
+  /**
+   * @param {EntityId} [playerEntity=null] - Player entity ID for chasing behavior
+   */
+  constructor(playerEntity = null) {
+    super();
+    /** @type {EntityId|null} */
+    this.playerEntity = playerEntity;
+  }
+
+  /**
+   * Set the player entity for chasing obstacles
+   * @param {EntityId} playerEntity
+   */
+  setPlayerEntity(playerEntity) {
+    this.playerEntity = playerEntity;
+  }
+
+  update(deltaTime) {
     const obstacles = this.getEntities(ObstacleTag, Transform, Velocity, BoundaryConstrained);
 
+    // Get player position if available
+    let playerPosition = null;
+    if (this.playerEntity) {
+      const playerTransform = this.getComponent(this.playerEntity, Transform);
+      if (playerTransform) {
+        playerPosition = playerTransform.position;
+      }
+    }
+
     for (const entityId of obstacles) {
       const transform = this.getComponent(entityId, Transform);
       const velocity = this.getComponent(entityId, Velocity);
       const boundary = this.getComponent(entityId, BoundaryConstrained);
+      const obstacleType = this.getComponent(entityId, ObstacleType);
+      const meshComp = this.getComponent(entityId, MeshComponent);
+
+      // Handle different obstacle types
+      if (obstacleType) {
+        // Chasing obstacles - move toward player
+        if (obstacleType.chases && playerPosition) {
+          const direction = playerPosition.clone().sub(transform.position);
+          direction.y = 0;
+          direction.normalize();
+          const chaseSpeed = 0.08 * obstacleType.speedMultiplier;
+          velocity.velocity.x = direction.x * chaseSpeed;
+          velocity.velocity.z = direction.z * chaseSpeed;
+        }
+
+        // Spinning obstacles - rotate faster
+        if (obstacleType.spins && meshComp) {
+          transform.rotation.y += 6 * obstacleType.rotationSpeed * deltaTime;
+        }
+      }
 
       const boundaryLimit = boundary.getBoundary() - 1;
 

src/systems/ParticleSystem.js

@@ -0,0 +1,106 @@
+import { System } from '../ecs/System.js';
+import { Transform } from '../components/Transform.js';
+import { ParticleEmitter } from '../components/ParticleEmitter.js';
+import { GameConfig } from '../game/GameConfig.js';
+
+/**
+ * ParticleSystem - manages particle effects for visual feedback
+ */
+export class ParticleSystem extends System {
+  constructor(scene) {
+    super();
+    /** @type {import('three').Scene} */
+    this.scene = scene;
+    
+    /** @type {Array<{mesh: import('three').Mesh, velocity: import('three').Vector3, lifetime: number, maxLifetime: number}>} */
+    this.particles = [];
+  }
+
+  /**
+   * Create particles at a position
+   * @param {import('three').Vector3} position - Position to emit from
+   * @param {number} count - Number of particles
+   * @param {number} color - Color (hex)
+   * @param {number} [speed=5] - Particle speed
+   */
+  emit(position, count, color, speed = 5) {
+    for (let i = 0; i < count; i++) {
+      const geometry = new window.THREE.SphereGeometry(0.1, 8, 8);
+      const material = new window.THREE.MeshBasicMaterial({
+        color: color,
+        transparent: true,
+        opacity: 1.0
+      });
+      const mesh = new window.THREE.Mesh(geometry, material);
+      mesh.position.copy(position);
+      this.scene.add(mesh);
+
+      // Random velocity direction
+      const velocity = new window.THREE.Vector3(
+        (Math.random() - 0.5) * speed,
+        Math.random() * speed * 0.5 + speed * 0.5,
+        (Math.random() - 0.5) * speed
+      );
+
+      this.particles.push({
+        mesh: mesh,
+        velocity: velocity,
+        lifetime: GameConfig.PARTICLE_LIFETIME,
+        maxLifetime: GameConfig.PARTICLE_LIFETIME
+      });
+    }
+  }
+
+  /**
+   * Update particles
+   * @param {number} deltaTime - Time since last frame in seconds
+   */
+  update(deltaTime) {
+    // Update existing particles
+    for (let i = this.particles.length - 1; i >= 0; i--) {
+      const particle = this.particles[i];
+      
+      // Update position
+      particle.mesh.position.add(
+        particle.velocity.clone().multiplyScalar(deltaTime)
+      );
+      
+      // Apply gravity
+      particle.velocity.y -= 9.8 * deltaTime;
+      
+      // Update lifetime
+      particle.lifetime -= deltaTime;
+      
+      // Fade out
+      const alpha = particle.lifetime / particle.maxLifetime;
+      particle.mesh.material.opacity = alpha;
+      
+      // Remove dead particles
+      if (particle.lifetime <= 0) {
+        this.scene.remove(particle.mesh);
+        particle.mesh.geometry.dispose();
+        particle.mesh.material.dispose();
+        this.particles.splice(i, 1);
+      }
+    }
+
+    // Process particle emitters from entities
+    const entities = this.getEntities(Transform, ParticleEmitter);
+    for (const entityId of entities) {
+      const transform = this.getComponent(entityId, Transform);
+      const emitter = this.getComponent(entityId, ParticleEmitter);
+      
+      if (emitter && emitter.active) {
+        this.emit(
+          transform.position,
+          emitter.count,
+          emitter.color,
+          emitter.speed
+        );
+        // Deactivate after emitting once
+        emitter.active = false;
+      }
+    }
+  }
+}
+

src/systems/PlayerControlSystem.js

@@ -3,13 +3,30 @@ import { PlayerTag } from '../components/Tags.js';
 import { Velocity } from '../components/Velocity.js';
 import { Transform } from '../components/Transform.js';
 
+/**
+ * @typedef {import('./PowerUpSystem.js').PowerUpSystem} PowerUpSystem
+ */
+
 /**
  * PlayerControlSystem - handles player input and applies to velocity
  */
 export class PlayerControlSystem extends System {
-  constructor(inputSystem) {
+  /**
+   * @param {InputSystem} inputSystem - Input system for reading controls
+   * @param {PowerUpSystem} [powerUpSystem=null] - Power-up system for speed multiplier
+   */
+  constructor(inputSystem, powerUpSystem = null) {
     super();
     this.inputSystem = inputSystem;
+    this.powerUpSystem = powerUpSystem;
+  }
+
+  /**
+   * Set the power-up system
+   * @param {PowerUpSystem} powerUpSystem
+   */
+  setPowerUpSystem(powerUpSystem) {
+    this.powerUpSystem = powerUpSystem;
   }
 
   update(deltaTime) {
@@ -19,30 +36,34 @@ export class PlayerControlSystem extends System {
       const velocity = this.getComponent(entityId, Velocity);
       const transform = this.getComponent(entityId, Transform);
 
+      // Get speed multiplier from power-up system
+      const speedMultiplier = this.powerUpSystem ? this.powerUpSystem.speedMultiplier : 1.0;
+      const effectiveMaxSpeed = velocity.maxSpeed * speedMultiplier;
+
       // Calculate target velocity from input
       const targetVelocity = new window.THREE.Vector3(0, 0, 0);
 
       // Keyboard input
       if (this.inputSystem.isKeyPressed('w') || this.inputSystem.isKeyPressed('up')) {
-        targetVelocity.z -= velocity.maxSpeed;
+        targetVelocity.z -= effectiveMaxSpeed;
       }
       if (this.inputSystem.isKeyPressed('s') || this.inputSystem.isKeyPressed('down')) {
-        targetVelocity.z += velocity.maxSpeed;
+        targetVelocity.z += effectiveMaxSpeed;
       }
       if (this.inputSystem.isKeyPressed('a') || this.inputSystem.isKeyPressed('left')) {
-        targetVelocity.x -= velocity.maxSpeed;
+        targetVelocity.x -= effectiveMaxSpeed;
       }
       if (this.inputSystem.isKeyPressed('d') || this.inputSystem.isKeyPressed('right')) {
-        targetVelocity.x += velocity.maxSpeed;
+        targetVelocity.x += effectiveMaxSpeed;
       }
 
       // Touch input
       const touch = this.inputSystem.getTouchDirection();
       if (Math.abs(touch.x) > 0.3) {
-        targetVelocity.x = touch.x * velocity.maxSpeed;
+        targetVelocity.x = touch.x * effectiveMaxSpeed;
       }
       if (Math.abs(touch.y) > 0.3) {
-        targetVelocity.z = touch.y * velocity.maxSpeed;
+        targetVelocity.z = touch.y * effectiveMaxSpeed;
       }
 
       // Apply smooth acceleration/deceleration

src/systems/PowerUpSystem.js

@@ -0,0 +1,133 @@
+import { System } from '../ecs/System.js';
+import { PowerUp } from '../components/PowerUp.js';
+import { Transform } from '../components/Transform.js';
+import { Velocity } from '../components/Velocity.js';
+import { PlayerTag } from '../components/Tags.js';
+import { GameConfig } from '../game/GameConfig.js';
+
+/**
+ * PowerUpSystem - manages active power-up effects on the player
+ */
+export class PowerUpSystem extends System {
+  /**
+   * @param {EntityId} [playerEntity=null] - Player entity ID
+   */
+  constructor(playerEntity = null) {
+    super();
+    /** @type {EntityId|null} */
+    this.playerEntity = playerEntity;
+    
+    /** @type {Object<string, PowerUp>} Active power-ups by type */
+    this.activePowerUps = {};
+    
+    /** @type {number} Base speed multiplier (1.0 = normal) */
+    this.speedMultiplier = 1.0;
+    
+    /** @type {number} Score multiplier (1.0 = normal) */
+    this.scoreMultiplier = 1.0;
+    
+    /** @type {boolean} Whether magnet is active */
+    this.magnetActive = false;
+  }
+
+  /**
+   * Set the player entity
+   * @param {EntityId} playerEntity
+   */
+  setPlayerEntity(playerEntity) {
+    this.playerEntity = playerEntity;
+  }
+
+  /**
+   * Activate a power-up
+   * @param {string} type - Power-up type
+   * @param {number} duration - Duration in seconds
+   */
+  activatePowerUp(type, duration) {
+    this.activePowerUps[type] = new PowerUp(type, duration);
+    this.updateEffects();
+  }
+
+  /**
+   * Update active power-up effects
+   */
+  updateEffects() {
+    // Reset all effects
+    this.speedMultiplier = 1.0;
+    this.scoreMultiplier = 1.0;
+    this.magnetActive = false;
+
+    // Apply active power-ups
+    for (const [type, powerUp] of Object.entries(this.activePowerUps)) {
+      if (powerUp.active && powerUp.timeRemaining > 0) {
+        switch (type) {
+          case 'speed':
+            this.speedMultiplier = GameConfig.POWERUP_SPEED_MULTIPLIER;
+            break;
+          case 'multiplier':
+            this.scoreMultiplier = GameConfig.POWERUP_SCORE_MULTIPLIER;
+            break;
+          case 'magnet':
+            this.magnetActive = true;
+            break;
+          case 'shield':
+            // Shield is handled separately in collision system
+            break;
+        }
+      }
+    }
+  }
+
+  /**
+   * Check if a power-up type is active
+   * @param {string} type - Power-up type
+   * @returns {boolean}
+   */
+  isActive(type) {
+    const powerUp = this.activePowerUps[type];
+    return powerUp && powerUp.active && powerUp.timeRemaining > 0;
+  }
+
+  /**
+   * Update power-ups and apply magnet effect
+   * @param {number} deltaTime - Time since last frame in seconds
+   */
+  update(deltaTime) {
+    // Update all active power-ups
+    for (const [type, powerUp] of Object.entries(this.activePowerUps)) {
+      if (!powerUp.update(deltaTime)) {
+        // Power-up expired
+        delete this.activePowerUps[type];
+      }
+    }
+
+    // Update effects
+    this.updateEffects();
+
+    // Apply magnet effect - attract coins to player
+    if (this.magnetActive && this.playerEntity) {
+      const playerTransform = this.getComponent(this.playerEntity, Transform);
+      if (!playerTransform) return;
+
+      // Get all coins
+      const coins = this.getEntities(Transform);
+      for (const coinId of coins) {
+        const coinTransform = this.getComponent(coinId, Transform);
+        if (!coinTransform) continue;
+
+        const distance = playerTransform.position.distanceTo(coinTransform.position);
+        
+        if (distance < GameConfig.POWERUP_MAGNET_RANGE && distance > 0.5) {
+          // Attract coin to player
+          const direction = playerTransform.position.clone().sub(coinTransform.position);
+          direction.y = 0;
+          direction.normalize();
+          
+          const attractSpeed = 0.15;
+          coinTransform.position.add(direction.multiplyScalar(attractSpeed * deltaTime * 60));
+        }
+      }
+    }
+  }
+}
+