Micro 3D Arcade Kart Racing Benchmark

You are an expert Three.js game engineer. Build a complete, polished, bug-free, self-contained 3D Arcade Kart Racing game in a single standalone `index.html` file.

Zero external assets (no images, GLTF models, audio files, or CSS frameworks). Three.js must be loaded from a public CDN (e.g. `https://cdnjs.cloudflare.com/ajax/libs/three.js/r128/three.min.js`). All 3D models (karts, track, trees, arches, items) must be constructed procedurally using Three.js geometries and materials.

### Requirements:
1. 3D Race Track & Environment:
   - Closed-loop circuit with straights, sweeping curves, chicanes, and elevation changes or banked turns.
   - Distinct asphalt road surface, red-and-white alternating curb borders, and a 3D Start/Finish gantry arch with a checkered banner texture generated on canvas.
   - Surrounding environment: Low-poly terrain, decorative trees, tire barriers, and spectator stands or neon banners.
   - Proper lighting: Ambient lighting + Directional light with soft shadows enabled.

2. Kart Modeling & Arcade Physics:
   - Build procedural low-poly karts (chassis, 4 spinning wheels, spoiler, driver helmet/steering wheel).
   - Responsive arcade driving physics: Acceleration, maximum top speed, coasting friction, reverse, and proportional steering.
   - Drift Mechanic: Pressing Spacebar or Shift while turning initiates a drift. Drifting tightens the turn radius, emits tire smoke particles from rear wheels, and triggers a mini-turbo boost when released after a long drift.
   - Collision response: Hitting track barriers bounces the kart and reduces speed.

3. AI Opponent Racers:
   - Include 2 AI rival karts with distinct colored chassis (e.g., Red for Player, Blue and Yellow for AI rivals).
   - AI karts navigate track waypoints intelligently with smooth steering, dynamic speed adjustments, and basic obstacle avoidance.

4. Race System, HUD & Timing:
   - 3-Lap Grand Prix race structure.
   - Race Start countdown: 3 -> 2 -> 1 -> GO! (player and AI cannot move until GO).
   - Floating UI Overlay HUD displaying:
     - Current Position: 1st / 2nd / 3rd (calculated dynamically based on track progression and lap count).
     - Lap Counter: Current Lap / 3.
     - Live Lap Timer and Best Lap record.
     - Digital / Analog Speedometer (km/h or MPH).
     - Mini-map radar showing player and AI positions on the circuit.

5. Boost Pads & Collectible Power-ups:
   - Glowing neon Boost Pads placed on track that give an immediate 2-second Nitro boost with speed lines or camera FOV surge.
   - Collectible rotating 3D Item Boxes on track granting power-ups (e.g., Nitro Boost, Homing Missile, or Banana Trap).

6. Audio Synthesis (Zero External Files):
   - Real-time procedural sound effects synthesized via Web Audio API:
     - Dynamic engine acceleration sound (pitch scales with kart speed).
     - Tire screeching sound during drifts.
     - Boost pad activation chime.
     - Race finish victory fanfare.
   - Master Mute / Unmute sound toggle button.

7. Camera System & Mobile/Keyboard Controls:
   - Third-person smooth chase camera following behind the player kart with subtle banking tilt and velocity lag.
   - Controls: Arrow keys / WASD for driving + Spacebar for drift/item. Include on-screen virtual touch buttons for mobile/tablet play.

8. Complete State Flow:
   - Title / Start Screen ("Press Start Race") -> 3-2-1 Countdown -> Active Race -> Finish / Podium Result Screen with Lap Breakdown -> Restart Race button.