diff --git a/index.html b/index.html
index 3117536..63d7c83 100644
--- a/index.html
+++ b/index.html
@@ -96,6 +96,20 @@
             z-index: 100;
             font-family: 'Courier New', monospace;
         }
+        #soundStatus {
+            position: absolute;
+            top: 20px;
+            right: 100px;
+            font-size: 20px;
+            cursor: pointer;
+            z-index: 100;
+            user-select: none;
+            opacity: 0.8;
+            transition: opacity 0.2s;
+        }
+        #soundStatus:hover {
+            opacity: 1;
+        }
         #perfMonitor {
             position: absolute;
             top: 60px;
@@ -125,6 +139,11 @@
                 top: 10px;
                 right: 10px;
             }
+            #soundStatus {
+                top: 10px;
+                right: 60px;
+                font-size: 18px;
+            }
             #perfMonitor {
                 top: 40px;
                 right: 10px;
@@ -144,6 +163,8 @@
     
     <div id="version">v<span id="versionNumber">-</span></div>
     
+    <div id="soundStatus" title="Sound ON (Press M to mute)">🔊</div>
+    
     <div id="perfMonitor">
         <div><span class="label">FPS:</span> <span id="fps">60</span></div>
         <div><span class="label">Frame:</span> <span id="frameTime">16.7</span>ms</div>
@@ -159,7 +180,7 @@
     
     <div id="instructions">
         <p><strong>Controls:</strong> WASD or Arrow Keys to move | Touch and drag to move (mobile) | Collect yellow coins | Avoid red obstacles!</p>
-        <p style="margin-top: 5px; font-size: 11px; opacity: 0.7;">Press "T" or shake device to toggle performance monitor</p>
+        <p style="margin-top: 5px; font-size: 11px; opacity: 0.7;">Press "T" to toggle performance monitor | Press "M" to toggle sound</p>
     </div>
 
     <script type="module">
diff --git a/nginx.conf b/nginx.conf
index 2c3229d..eee0bb3 100644
--- a/nginx.conf
+++ b/nginx.conf
@@ -9,6 +9,27 @@ server {
         try_files $uri $uri/ =404;
     }
     
+    # Prevent caching of JavaScript files and version.json
+    location ~* \.(js|mjs)$ {
+        add_header Cache-Control "no-cache, no-store, must-revalidate";
+        add_header Pragma "no-cache";
+        add_header Expires "0";
+        add_header Vary "Accept-Encoding";
+    }
+    
+    location = /version.json {
+        add_header Cache-Control "no-cache, no-store, must-revalidate";
+        add_header Pragma "no-cache";
+        add_header Expires "0";
+    }
+    
+    # Prevent caching of HTML
+    location ~* \.html$ {
+        add_header Cache-Control "no-cache, no-store, must-revalidate";
+        add_header Pragma "no-cache";
+        add_header Expires "0";
+    }
+    
     # Enable gzip compression
     gzip on;
     gzip_types text/html text/css application/javascript;
diff --git a/src/components/CoinType.js b/src/components/CoinType.js
new file mode 100644
index 0000000..fc989e6
--- /dev/null
+++ b/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;
+    }
+  }
+}
+
diff --git a/src/components/ObstacleType.js b/src/components/ObstacleType.js
new file mode 100644
index 0000000..c003531
--- /dev/null
+++ b/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;
+  }
+}
+
diff --git a/src/components/ParticleEmitter.js b/src/components/ParticleEmitter.js
new file mode 100644
index 0000000..8afac89
--- /dev/null
+++ b/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;
+  }
+}
+
diff --git a/src/components/PowerUp.js b/src/components/PowerUp.js
new file mode 100644
index 0000000..adec6df
--- /dev/null
+++ b/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;
+  }
+}
+
diff --git a/src/components/SoundEvent.js b/src/components/SoundEvent.js
new file mode 100644
index 0000000..7764a0a
--- /dev/null
+++ b/src/components/SoundEvent.js
@@ -0,0 +1,21 @@
+/**
+ * SoundEvent component - represents a sound that should be played
+ * Entities can add this component to trigger sounds, which SoundSystem will process
+ */
+export class SoundEvent {
+  /**
+   * @param {string} type - Sound type: 'coin', 'damage', 'powerup', 'combo', 'health', 'gameover', 'highscore'
+   * @param {number} [value] - Optional value (e.g., combo multiplier)
+   */
+  constructor(type, value = null) {
+    /** @type {string} Sound event type */
+    this.type = type;
+    
+    /** @type {number|null} Optional value for the sound (e.g., combo multiplier) */
+    this.value = value;
+    
+    /** @type {boolean} Whether this event has been processed */
+    this.processed = false;
+  }
+}
+
diff --git a/src/game/EntityFactory.js b/src/game/EntityFactory.js
index f398994..0b0c505 100644
--- a/src/game/EntityFactory.js
+++ b/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
diff --git a/src/game/Game.js b/src/game/Game.js
index 76aef4c..6f1e9da 100644
--- a/src/game/Game.js
+++ b/src/game/Game.js
@@ -11,12 +11,18 @@ 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 { SoundSystem } from '../systems/SoundSystem.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';
+import { SoundEvent } from '../components/SoundEvent.js';
 
 /**
  * Main Game class - manages the game loop and coordinates all systems.
@@ -46,6 +52,9 @@ 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 +98,23 @@ 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 +212,17 @@ 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 +230,19 @@ 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) => {
@@ -207,6 +250,10 @@ export class Game {
     });
     this.world.addSystem(this.collisionSystem);
 
+    // Sound system (processes SoundEvent components)
+    this.soundSystem = new SoundSystem();
+    this.world.addSystem(this.soundSystem);
+
     // Rendering (must be last to sync transforms)
     this.world.addSystem(new RenderSystem(this.scene));
   }
@@ -214,6 +261,14 @@ export class Game {
   createGameEntities() {
     // 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++) {
@@ -221,7 +276,7 @@ export class Game {
       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 +292,12 @@ 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 +307,19 @@ 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;
+
+    // Emit sound event BEFORE destroying the entity
+    const soundEntity = this.world.createEntity();
+    if (coinType && coinType.type === 'health') {
+      this.world.addComponent(soundEntity, new SoundEvent('health'));
+    } else {
+      this.world.addComponent(soundEntity, new SoundEvent('coin'));
+    }
+
     // Remove coin
     this.entityFactory.destroyEntity(coinEntity);
     const index = this.coins.indexOf(coinEntity);
@@ -253,17 +327,60 @@ 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;
 
     if (timeSinceLastCoin <= GameConfig.COMBO_TIME_WINDOW && this.lastCoinTime > 0) {
       // Maintain combo
+      const oldMultiplier = this.comboMultiplier;
       this.comboMultiplier = Math.min(
         this.comboMultiplier + 1,
         GameConfig.COMBO_MULTIPLIER_MAX
       );
       this.comboTimer = GameConfig.COMBO_TIME_WINDOW;
+      
+      // Emit combo sound event if multiplier increased
+      if (this.comboMultiplier > oldMultiplier) {
+        // Create temporary entity for combo sound
+        const comboEntity = this.world.createEntity();
+        this.world.addComponent(comboEntity, new SoundEvent('combo', this.comboMultiplier));
+      }
     } else {
       // Reset combo
       this.comboMultiplier = 1;
@@ -272,25 +389,106 @@ 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
     if (this.score > this.highScore) {
       this.highScore = this.score;
       this.saveHighScore(this.highScore);
+      // Emit high score sound event
+      const highScoreEntity = this.world.createEntity();
+      this.world.addComponent(highScoreEntity, new SoundEvent('highscore'));
     }
 
     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 power-up sound event
+      const powerUpSoundEntity = this.world.createEntity();
+      this.world.addComponent(powerUpSoundEntity, new SoundEvent('powerup'));
+    }
+
+    // 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 +507,19 @@ 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;
@@ -320,6 +531,10 @@ export class Game {
     this.comboMultiplier = 1;
     this.comboTimer = 0;
 
+    // Emit damage sound event
+    const damageSoundEntity = this.world.createEntity();
+    this.world.addComponent(damageSoundEntity, new SoundEvent('damage'));
+
     this.updateUI();
 
     if (isDead) {
@@ -332,8 +547,20 @@ 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);
     }
   }
@@ -376,6 +603,10 @@ export class Game {
       newHighScoreEl.style.display = 'none';
     }
     
+    // Emit game over sound event
+    const gameOverEntity = this.world.createEntity();
+    this.world.addComponent(gameOverEntity, new SoundEvent('gameover'));
+    
     document.getElementById('gameOver').style.display = 'block';
   }
 
@@ -383,12 +614,14 @@ 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;
@@ -402,6 +635,14 @@ 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();
@@ -420,6 +661,10 @@ export class Game {
       if (e.key.toLowerCase() === 't') {
         this.togglePerformanceMonitor();
       }
+      // Toggle sound with 'M' key
+      if (e.key.toLowerCase() === 'm') {
+        this.toggleSound();
+      }
     });
 
     // Shake detection for mobile
@@ -454,6 +699,28 @@ export class Game {
 
     // Load version
     this.loadVersion();
+    
+    // Setup sound status click handler
+    const soundStatusEl = document.getElementById('soundStatus');
+    if (soundStatusEl) {
+      soundStatusEl.addEventListener('click', async () => {
+        this.toggleSound();
+
+      });
+    }
+    
+    // Initialize sound system on first click anywhere
+    document.addEventListener('click', () => {
+      if (this.soundSystem && this.soundSystem.isEnabled()) {
+        console.log('Sound system ready, state:', this.soundSystem.getState());
+        // Start background music after initialization
+        if (this.soundSystem.isEnabled()) {
+          this.soundSystem.startBackgroundMusic().catch(err => {
+            console.warn('Failed to start background music:', err);
+          });
+        }
+      }
+    }, { once: true });
   }
 
   /**
@@ -471,6 +738,31 @@ export class Game {
     }
   }
 
+  /**
+   * Toggle sound on/off
+   */
+  toggleSound() {
+    if (this.soundSystem) {
+      const enabled = this.soundSystem.toggle();
+      const soundStatusEl = document.getElementById('soundStatus');
+      if (soundStatusEl) {
+        soundStatusEl.textContent = enabled ? '🔊' : '🔇';
+        soundStatusEl.title = enabled ? 'Sound ON (Press M to mute)' : 'Sound OFF (Press M to unmute)';
+      }
+      
+      // Start/stop background music based on sound state
+      if (enabled) {
+        this.soundSystem.startBackgroundMusic().catch(err => {
+          console.warn('Failed to start background music:', err);
+        });
+      } else {
+        this.soundSystem.stopBackgroundMusic();
+      }
+      
+      console.log('Sound', enabled ? 'enabled' : 'disabled');
+    }
+  }
+
   /**
    * Handle device motion for shake detection
    * @param {DeviceMotionEvent} event
@@ -509,7 +801,11 @@ export class Game {
   }
 
   loadVersion() {
-    fetch('/version.json')
+    // Add cache-busting query parameter to ensure fresh version data
+    const cacheBuster = `?t=${Date.now()}`;
+    fetch(`/version.json${cacheBuster}`, {
+      cache: 'no-store'
+    })
       .then(response => {
         if (response.ok) {
           return response.json();
@@ -527,6 +823,33 @@ 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
@@ -598,6 +921,11 @@ 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) {
@@ -611,11 +939,17 @@ export class Game {
         const health = this.world.getComponent(this.playerEntity, Health);
         if (health && health.currentHealth < health.maxHealth) {
           health.heal(GameConfig.HEALTH_REGEN_AMOUNT);
+          // Emit health regen sound event
+          const healthRegenEntity = this.world.createEntity();
+          this.world.addComponent(healthRegenEntity, new SoundEvent('health'));
           this.updateUI();
         }
         this.healthRegenTimer = 0;
       }
 
+      // Difficulty scaling - add obstacles over time
+      this.updateDifficulty(deltaTime);
+
       // Update ECS world with actual deltaTime
       this.world.update(deltaTime);
 
diff --git a/src/game/GameConfig.js b/src/game/GameConfig.js
index 3fd6de1..03e9f02 100644
--- a/src/game/GameConfig.js
+++ b/src/game/GameConfig.js
@@ -4,7 +4,7 @@
  */
 export const GameConfig = {
   // Gameplay
-  OBSTACLE_DAMAGE: 3, // Increased from 1 to balance invincibility frames and health regen
+  OBSTACLE_DAMAGE: 5, // Increased from 3 - obstacles should be more dangerous
   COIN_SCORE: 10,
   HEALTH_REGEN_INTERVAL: 10, // Heal 1 HP every 10 seconds
   HEALTH_REGEN_AMOUNT: 1,
@@ -15,12 +15,34 @@ export const GameConfig = {
   COMBO_BASE_SCORE: 10, // Base score per coin
   
   // Invincibility
-  INVINCIBILITY_DURATION: 1.5, // Seconds of invincibility after damage
+  INVINCIBILITY_DURATION: 0.8, // Reduced from 1.5 to 0.8 seconds - shorter invincibility window
   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,
diff --git a/src/systems/ObstacleSystem.js b/src/systems/ObstacleSystem.js
index 92826a6..263a93b 100644
--- a/src/systems/ObstacleSystem.js
+++ b/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;
 
diff --git a/src/systems/ParticleSystem.js b/src/systems/ParticleSystem.js
new file mode 100644
index 0000000..d1f2e7d
--- /dev/null
+++ b/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;
+      }
+    }
+  }
+}
+
diff --git a/src/systems/PlayerControlSystem.js b/src/systems/PlayerControlSystem.js
index 5c71304..f6b75df 100644
--- a/src/systems/PlayerControlSystem.js
+++ b/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
diff --git a/src/systems/PowerUpSystem.js b/src/systems/PowerUpSystem.js
new file mode 100644
index 0000000..edeb8d2
--- /dev/null
+++ b/src/systems/PowerUpSystem.js
@@ -0,0 +1,131 @@
+import { System } from '../ecs/System.js';
+import { PowerUp } from '../components/PowerUp.js';
+import { Transform } from '../components/Transform.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));
+        }
+      }
+    }
+  }
+}
+
diff --git a/src/systems/SoundSystem.js b/src/systems/SoundSystem.js
new file mode 100644
index 0000000..4b70910
--- /dev/null
+++ b/src/systems/SoundSystem.js
@@ -0,0 +1,584 @@
+import { System } from '../ecs/System.js';
+import { SoundEvent } from '../components/SoundEvent.js';
+
+/**
+ * SoundSystem - Lightweight sound system using Web Audio API (no external dependencies)
+ * Generates simple procedural sound effects
+ * Follows ECS pattern: processes SoundEvent components from entities
+ */
+export class SoundSystem extends System {
+  constructor() {
+    super();
+
+    /** @type {AudioContext|null} Web Audio API context */
+    this.audioContext = null;
+
+    /** @type {boolean} Whether sound is enabled */
+    this.enabled = true;
+
+    /** @type {boolean} Whether audio context is initialized */
+    this.initialized = false;
+
+    /** @type {OscillatorNode[]} Active background music oscillators */
+    this.bgMusicOscillators = [];
+
+    /** @type {GainNode|null} Background music gain node */
+    this.bgMusicGain = null;
+
+    /** @type {boolean} Whether background music is playing */
+    this.bgMusicPlaying = false;
+
+    /** @type {number} Background music volume (0-1) */
+    this.bgMusicVolume = 0.25; // Increased from 0.15 for better audibility
+
+    // Initialize on first user interaction (browser requirement)
+    this.initOnInteraction();
+  }
+
+  /**
+   * Called when system is added to world
+   */
+  init() {
+    if (this.enabled && !this.bgMusicPlaying) {
+      this.startBackgroundMusic().catch(err => {
+        console.warn('Failed to auto-start background music:', err);
+      });
+    }
+  }
+
+  /**
+   * Update - processes SoundEvent components
+   * @param {number} _deltaTime - Time since last frame (not used for sound events)
+   */
+  update(_deltaTime) {
+    // Process all SoundEvent components
+    const soundEvents = this.getEntities(SoundEvent);
+
+    for (const entityId of soundEvents) {
+      const soundEvent = this.getComponent(entityId, SoundEvent);
+
+      if (soundEvent && !soundEvent.processed) {
+        // Play the appropriate sound based on type
+        this.playSoundEvent(soundEvent);
+
+        // Mark as processed and remove component
+        soundEvent.processed = true;
+        this.world.removeComponent(entityId, SoundEvent);
+      }
+    }
+  }
+
+  /**
+   * Play a sound event
+   * @param {SoundEvent} soundEvent - The sound event to play
+   */
+  playSoundEvent(soundEvent) {
+    if (!this.enabled) return;
+
+    // All sound methods are async, handle them properly
+    const playSound = async (soundMethod) => {
+      try {
+        await soundMethod();
+      } catch (error) {
+        // Silently ignore sound errors
+      }
+    };
+
+    switch (soundEvent.type) {
+      case 'coin':
+        playSound(() => this.playCoinCollect());
+        break;
+      case 'damage':
+        playSound(() => this.playDamage());
+        break;
+      case 'powerup':
+        playSound(() => this.playPowerUp());
+        break;
+      case 'combo':
+        playSound(() => this.playCombo(soundEvent.value || 1));
+        break;
+      case 'health':
+        playSound(() => this.playHealthRegen());
+        break;
+      case 'gameover':
+        playSound(() => this.playGameOver());
+        break;
+      case 'highscore':
+        playSound(() => this.playHighScore());
+        break;
+      default:
+        console.warn('Unknown sound event type:', soundEvent.type);
+    }
+  }
+
+  /**
+   * Initialize audio context on first user interaction
+   */
+  initOnInteraction() {
+    const initAudio = async () => {
+      if (!this.initialized) {
+        try {
+          this.audioContext = new (window.AudioContext || window.webkitAudioContext)();
+          this.initialized = true;
+
+          // Resume if suspended
+          if (this.audioContext.state === 'suspended') {
+            await this.audioContext.resume();
+          }
+        } catch (error) {
+          console.warn('Web Audio API not supported:', error);
+          this.enabled = false;
+        }
+      }
+    };
+
+    // Initialize on any user interaction
+    ['click', 'touchstart', 'keydown', 'mousedown'].forEach(event => {
+      document.addEventListener(event, initAudio, { once: true });
+    });
+  }
+
+  /**
+   * Ensure audio context is initialized and resumed
+   * @returns {boolean} True if audio is ready (synchronous check)
+   */
+  ensureInitialized() {
+    if (!this.enabled) return false;
+
+    // Create audio context if it doesn't exist
+    if (!this.audioContext) {
+      try {
+        this.audioContext = new (window.AudioContext || window.webkitAudioContext)();
+        this.initialized = true;
+      } catch (error) {
+        console.warn('Failed to create audio context:', error);
+        return false;
+      }
+    }
+
+    // Try to resume if suspended (non-blocking - will resume on next interaction if needed)
+    if (this.audioContext.state === 'suspended') {
+      this.audioContext.resume().then(() => {
+        console.log('Audio context resumed');
+      }).catch(error => {
+        console.warn('Failed to resume audio context:', error);
+      });
+    }
+
+    return this.initialized && this.enabled;
+  }
+
+  /**
+   * Play a tone
+   * @param {number} frequency - Frequency in Hz
+   * @param {number} duration - Duration in seconds
+   * @param {string} type - Waveform type ('sine', 'square', 'sawtooth', 'triangle')
+   * @param {number} [volume=0.3] - Volume (0-1)
+   */
+  async playTone(frequency, duration, type = 'sine', volume = 0.3) {
+    const ready = this.ensureInitialized();
+    if (!ready || !this.audioContext) return;
+
+    try {
+      const oscillator = this.audioContext.createOscillator();
+      const gainNode = this.audioContext.createGain();
+
+      oscillator.connect(gainNode);
+      gainNode.connect(this.audioContext.destination);
+
+      oscillator.frequency.value = frequency;
+      oscillator.type = type;
+
+      // Envelope: quick attack, sustain, quick release
+      const now = this.audioContext.currentTime;
+      gainNode.gain.setValueAtTime(0, now);
+      gainNode.gain.linearRampToValueAtTime(volume, now + 0.01);
+      gainNode.gain.setValueAtTime(volume, now + duration * 0.7);
+      gainNode.gain.exponentialRampToValueAtTime(0.001, now + duration);
+
+      oscillator.start(now);
+      oscillator.stop(now + duration);
+    } catch (error) {
+      console.warn('Failed to play tone:', error);
+    }
+  }
+
+  /**
+   * Play a coin collection sound - metallic clinking like real coins
+   */
+  async playCoinCollect() {
+    // Metallic clink using multiple harmonics via playTone
+    // Main coin "clink" - high frequency
+    await this.playTone(800, 0.15, 'sine', 0.3);
+    await this.playTone(1200, 0.15, 'sine', 0.2);
+    await this.playTone(1600, 0.15, 'sine', 0.1);
+
+    // Second coin clink slightly delayed for "clinking" effect
+    setTimeout(() => {
+      if (this.enabled) {
+        this.playTone(1000, 0.1, 'sine', 0.25).catch(() => { });
+      }
+    }, 30);
+  }
+
+  /**
+   * Play a damage sound - "ouch" like human exclamation
+   */
+  async playDamage() {
+    await this.playTone(300, 0.2, 'sine', 0.4);
+    await this.playTone(600, 0.2, 'sine', 0.3);
+    await this.playTone(800, 0.2, 'sawtooth', 0.2);
+
+    // Add a quick "uh" sound at the end
+    setTimeout(() => {
+      if (this.enabled) {
+        this.playTone(250, 0.1, 'sine', 0.2).catch(() => { });
+      }
+    }, 100);
+  }
+
+  /**
+   * Play a power-up sound
+   */
+  playPowerUp() {
+    // Ascending arpeggio
+    const notes = [440, 554.37, 659.25, 783.99]; // A, C#, E, G
+    notes.forEach((freq, i) => {
+      setTimeout(() => {
+        if (this.enabled) {
+          this.playTone(freq, 0.15, 'sine', 0.25).catch(() => { });
+        }
+      }, i * 80);
+    });
+  }
+
+  /**
+   * Play a combo sound (higher multiplier = more notes)
+   * @param {number} multiplier - Combo multiplier
+   */
+  playCombo(multiplier) {
+    const baseFreq = 440;
+    const notes = Math.min(multiplier, 5);
+
+    for (let i = 0; i < notes; i++) {
+      setTimeout(() => {
+        if (this.enabled) {
+          const freq = baseFreq * (1 + i * 0.2);
+          this.playTone(freq, 0.1, 'sine', 0.15).catch(() => { });
+        }
+      }, i * 50);
+    }
+  }
+
+  /**
+   * Play a health regeneration sound
+   */
+  playHealthRegen() {
+    // Gentle ascending tone
+    this.playTone(330, 0.2, 'sine', 0.15).catch(() => { });
+    setTimeout(() => {
+      if (this.enabled) {
+        this.playTone(392, 0.2, 'sine', 0.15).catch(() => { });
+      }
+    }, 100);
+  }
+
+  /**
+   * Play a game over sound
+   */
+  playGameOver() {
+    // Descending sad tone
+    const notes = [440, 392, 349, 294]; // A, G, F, D
+    notes.forEach((freq, i) => {
+      setTimeout(() => {
+        if (this.enabled) {
+          this.playTone(freq, 0.3, 'sine', 0.3).catch(() => { });
+        }
+      }, i * 150);
+    });
+  }
+
+  /**
+   * Play a new high score sound
+   */
+  playHighScore() {
+    // Triumphant ascending scale
+    const notes = [523.25, 659.25, 783.99, 987.77]; // C, E, G, B
+    notes.forEach((freq, i) => {
+      setTimeout(() => {
+        if (this.enabled) {
+          this.playTone(freq, 0.2, 'sine', 0.3).catch(() => { });
+        }
+      }, i * 100);
+    });
+  }
+
+  /**
+   * Toggle sound on/off
+   * @returns {boolean} New enabled state
+   */
+  toggle() {
+    this.enabled = !this.enabled;
+    return this.enabled;
+  }
+
+  /**
+   * Set sound enabled state
+   * @param {boolean} enabled
+   */
+  setEnabled(enabled) {
+    this.enabled = enabled;
+  }
+
+  /**
+   * Check if sound is enabled
+   * @returns {boolean}
+   */
+  isEnabled() {
+    return this.enabled;
+  }
+
+  /**
+   * Get audio context state for debugging
+   * @returns {string} Audio context state
+   */
+  getState() {
+    if (!this.audioContext) return 'not initialized';
+    return this.audioContext.state;
+  }
+
+  /**
+   * Test sound - plays a simple tone to verify audio works
+   */
+  async testSound() {
+    console.log('Testing sound system...');
+    console.log('Audio context state:', this.getState());
+    await this.playTone(440, 0.2, 'sine', 0.5);
+    console.log('Test sound played');
+  }
+
+  /**
+   * Start background music - animated looping OST
+   */
+  async startBackgroundMusic() {
+    if (this.bgMusicPlaying) {
+      console.log('Background music already playing');
+      return;
+    }
+
+    const ready = this.ensureInitialized();
+    if (!ready || !this.audioContext) {
+      console.warn('Cannot start background music: audio context not ready, state:', this.getState());
+      return;
+    }
+
+    try {
+      this.bgMusicPlaying = true;
+      console.log('Starting background music, audio context state:', this.audioContext.state);
+
+      // Create gain node for background music volume control
+      this.bgMusicGain = this.audioContext.createGain();
+      this.bgMusicGain.gain.value = this.bgMusicVolume * 0.5;
+      this.bgMusicGain.connect(this.audioContext.destination);
+
+      // Electronic/EDM style music
+      // Simple chord progression: C - Am - F - G (I - vi - IV - V - classic electronic progression)
+      const chordProgression = [
+        [130.81, 164.81, 196], // C major (C, E, G)
+        [220, 261.63, 329.63], // Am (A, C, E)
+        [174.61, 220, 261.63], // F major (F, A, C)
+        [196, 246.94, 293.66]  // G major (G, B, D)
+      ];
+
+      // Electronic melody notes (higher octave, pentatonic for catchy hook)
+      const melodyNotes = [523.25, 587.33, 659.25, 698.46, 783.99, 880, 987.77, 1046.5]; // C5 to C6 - bright electronic range
+
+      // Bass line for electronic feel (lower octave)
+      const bassNotes = [65.41, 73.42, 82.41, 87.31, 98, 110, 123.47]; // C2 to B2
+
+      const playChord = (chord, startTime, duration) => {
+        chord.forEach((freq, index) => {
+          const osc = this.audioContext.createOscillator();
+          const gain = this.audioContext.createGain();
+
+          // Use sawtooth for electronic/analog synth feel
+          osc.type = 'sawtooth';
+          osc.frequency.value = freq;
+          osc.connect(gain);
+          gain.connect(this.bgMusicGain);
+
+          // Very bright, energetic attack for happy feel
+          gain.gain.setValueAtTime(0, startTime);
+          gain.gain.linearRampToValueAtTime(0.5, startTime + 0.1); // Very fast, bright attack
+          gain.gain.setValueAtTime(0.5, startTime + duration - 0.2);
+          gain.gain.linearRampToValueAtTime(0, startTime + duration);
+
+          osc.start(startTime);
+          osc.stop(startTime + duration);
+
+          this.bgMusicOscillators.push(osc);
+        });
+      };
+
+      const playMelody = (note, startTime, duration) => {
+        const osc = this.audioContext.createOscillator();
+        const gain = this.audioContext.createGain();
+
+        osc.type = 'square'; // Square wave for electronic lead
+        osc.frequency.value = note;
+        osc.connect(gain);
+        gain.connect(this.bgMusicGain);
+
+        // Very energetic, bouncy attack for happy melody
+        gain.gain.setValueAtTime(0, startTime);
+        gain.gain.linearRampToValueAtTime(0.4, startTime + 0.05); // Very quick, bright attack
+        gain.gain.setValueAtTime(0.4, startTime + duration - 0.05);
+        gain.gain.linearRampToValueAtTime(0, startTime + duration);
+
+        osc.start(startTime);
+        osc.stop(startTime + duration);
+
+        this.bgMusicOscillators.push(osc);
+      };
+
+      // Electronic bass line
+      const playBass = (note, startTime, duration) => {
+        const osc = this.audioContext.createOscillator();
+        const gain = this.audioContext.createGain();
+
+        osc.type = 'square'; // Square wave for electronic bass
+        osc.frequency.value = note;
+        osc.connect(gain);
+        gain.connect(this.bgMusicGain);
+
+        // Punchy bass envelope
+        gain.gain.setValueAtTime(0, startTime);
+        gain.gain.linearRampToValueAtTime(0.4, startTime + 0.02);
+        gain.gain.setValueAtTime(0.4, startTime + duration - 0.05);
+        gain.gain.exponentialRampToValueAtTime(0.001, startTime + duration);
+
+        osc.start(startTime);
+        osc.stop(startTime + duration);
+
+        this.bgMusicOscillators.push(osc);
+      };
+
+      // Loop function - creates 8 second loop (fast electronic tempo)
+      const loopDuration = 8; // seconds - fast electronic tempo
+      let nextLoopTime = this.audioContext.currentTime;
+
+      const scheduleLoop = () => {
+        if (!this.bgMusicPlaying || !this.audioContext) return;
+
+        const startTime = nextLoopTime;
+
+        // Play chord progression (4 chords, 2 seconds each - fast electronic tempo)
+        chordProgression.forEach((chord, chordIndex) => {
+          const chordStart = startTime + (chordIndex * 2);
+          playChord(chord, chordStart, 1.9);
+        });
+
+        // Electronic bass line (pulsing rhythm)
+        const bassPattern = [
+          { note: bassNotes[0], time: 0, duration: 0.3 },    // C - kick
+          { note: bassNotes[0], time: 0.5, duration: 0.2 },   // C
+          { note: bassNotes[2], time: 1.0, duration: 0.3 },  // E
+          { note: bassNotes[0], time: 1.5, duration: 0.2 },  // C
+          { note: bassNotes[3], time: 2.0, duration: 0.3 }, // F
+          { note: bassNotes[0], time: 2.5, duration: 0.2 },  // C
+          { note: bassNotes[4], time: 3.0, duration: 0.3 },  // G
+          { note: bassNotes[0], time: 3.5, duration: 0.2 },  // C
+          { note: bassNotes[2], time: 4.0, duration: 0.3 },  // E
+          { note: bassNotes[0], time: 4.5, duration: 0.2 },  // C
+          { note: bassNotes[3], time: 5.0, duration: 0.3 },  // F
+          { note: bassNotes[0], time: 5.5, duration: 0.2 },  // C
+          { note: bassNotes[4], time: 6.0, duration: 0.3 },  // G
+          { note: bassNotes[0], time: 6.5, duration: 0.2 },  // C
+          { note: bassNotes[2], time: 7.0, duration: 0.3 }   // E
+        ];
+
+        bassPattern.forEach(({ note, time, duration }) => {
+          playBass(note, startTime + time, duration);
+        });
+
+        // Play melody over chords (simpler pattern)
+        const melodyPattern = [
+          { note: melodyNotes[0], time: 0.5, duration: 1 },
+          { note: melodyNotes[2], time: 2, duration: 1 },
+          { note: melodyNotes[4], time: 4.5, duration: 1 },
+          { note: melodyNotes[3], time: 6, duration: 1 },
+          { note: melodyNotes[5], time: 8.5, duration: 1.5 },
+          { note: melodyNotes[4], time: 10.5, duration: 1 },
+          { note: melodyNotes[2], time: 12, duration: 1.5 },
+          { note: melodyNotes[0], time: 14, duration: 1.5 }
+        ];
+
+        melodyPattern.forEach(({ note, time, duration }) => {
+          playMelody(note, startTime + time, duration);
+        });
+
+        // Schedule next loop
+        nextLoopTime += loopDuration;
+
+        // Schedule next loop before current one ends (schedule 2 seconds before end)
+        const timeUntilNext = (nextLoopTime - this.audioContext.currentTime) * 1000 - 2000;
+
+        if (timeUntilNext > 0) {
+          setTimeout(() => {
+            if (this.bgMusicPlaying && this.audioContext) {
+              scheduleLoop();
+            }
+          }, timeUntilNext);
+        } else {
+          // If we're behind, schedule immediately
+          scheduleLoop();
+        }
+      };
+
+      // Start first loop immediately
+      scheduleLoop();
+
+      console.log('Background music started, audio context state:', this.audioContext.state);
+      console.log('Background music volume:', this.bgMusicVolume);
+    } catch (error) {
+      console.warn('Failed to start background music:', error);
+      this.bgMusicPlaying = false;
+    }
+  }
+
+  /**
+   * Stop background music
+   */
+  stopBackgroundMusic() {
+    this.bgMusicPlaying = false;
+
+    // Stop all oscillators
+    this.bgMusicOscillators.forEach(osc => {
+      try {
+        osc.stop();
+      } catch (e) {
+        // Oscillator might already be stopped
+      }
+    });
+    this.bgMusicOscillators = [];
+
+    if (this.bgMusicGain) {
+      this.bgMusicGain.disconnect();
+      this.bgMusicGain = null;
+    }
+
+    console.log('Background music stopped');
+  }
+
+  /**
+   * Set background music volume
+   * @param {number} volume - Volume (0-1)
+   */
+  setBackgroundMusicVolume(volume) {
+    this.bgMusicVolume = Math.max(0, Math.min(1, volume));
+    if (this.bgMusicGain) {
+      this.bgMusicGain.gain.value = this.bgMusicVolume;
+    }
+  }
+}
+