Implement DAS/ARR for smooth horizontal piece movement

public/js/audio.js

@@ -0,0 +1,34 @@
+// Audio Manager - Handles background music only
+
+class AudioManager {
+  constructor() {
+    this.bgMusic = document.getElementById('bg-music');
+    if (this.bgMusic) {
+      this.bgMusic.volume = 0.5;
+    }
+  }
+
+  playLobby() {
+    // No lobby music
+  }
+
+  playGame() {
+    if (!this.bgMusic) return;
+    this.bgMusic.src = '/audio/tetris_theme_og.mp3';
+    this.bgMusic.loop = true;
+    this.bgMusic.play().catch(e => console.log('Audio autoplay blocked:', e));
+  }
+
+  playGameOver() {
+    // No game over music
+  }
+
+  stop() {
+    if (!this.bgMusic) return;
+    this.bgMusic.pause();
+    this.bgMusic.currentTime = 0;
+  }
+}
+
+// Initialize audio manager
+const audio = new AudioManager();