Clone Mario Kart

Build a browser clone of Mario Kart — specifically Rainbow Road, with Mario Kart 8's drift and item
mechanics reproduced exactly — that is genuinely playable and genuinely feels like the real thing.

Context you should know: this is going into a video watched by a large audience, your build will be played
on camera against two other frontier models, and your work will be credited to you by name. Every model
gets this identical prompt. The audience has played this game. They will know immediately if the drift is
wrong, and "close enough" reads as failure. Go all out.

Requirements:

1. **Rainbow Road, reconstructed.** Not "a rainbow-themed track" — the actual thing: a narrow, guard-rail-less
   ribbon suspended in open space, banked turns, the signature drop, at least one split path, and the
   constant threat of falling off with a Lakitu-style respawn that drops you back on the track with a brief
   invulnerability and a speed penalty. Look up the layout and reproduce its character honestly. The track
   should be readable at speed — a first-time driver must be able to see where it goes.

2. **Mario Kart 8's drift model, exactly.** Hop-then-hold to initiate. Mini-turbo charges in three visible
   tiers while drifting — blue, then orange, then purple — each with its own spark color and its own boost
   duration on release. Counter-steer tightens or widens the slide. The kart has weight and the drift is
   controllable, not a slide-and-pray. **This is the single most important requirement in this prompt.** If
   the drift doesn't feel like Mario Kart, nothing else you build matters.

3. **Coins and speed.** Coins on the track, up to ten, each incrementally raising top speed. Taking a hit
   scatters them. This is load-bearing on the real game's feel and it is the detail most clones skip.

4. **The real item set, with the real roulette.** Item boxes that spin a roulette weighted by race position —
   the leader gets coins and bananas, the back of the pack gets the good stuff. At minimum: green shell
   (travels straight, bounces off walls), red shell (homes on the kart ahead), banana (drops behind, spins
   out whoever hits it), mushroom (instant boost), star (brief invulnerability plus speed), and a blue shell
   that seeks the leader. Each needs a visible pickup, a clear activation, and audible impact.

5. **Eight racers, three laps, real AI.** Seven AI opponents on genuine racing lines — outside-inside-outside,
   real braking points, they take the split path, they use items on each other and on you, they recover from
   spins and from falling off. Position-based rubber-banding matching the real game's is expected; obvious
   cheating is not.

6. **The full race structure.** Lap counter, position out of eight, coin count, item slot, speedometer, lap
   and total splits, and a track-position minimap. A three-two-one-GO countdown with a rocket-start window
   that rewards correct timing. A finish sequence and a results screen with placings and times.

7. **It has to look like a shipped game.** Real materials and lighting, shadows, and a coherent art direction
   held across the kart, the track and the skybox. Motion that sells speed: FOV punch on boost, drift sparks
   that visibly tier with the charge, tire marks, impact particles, screen shake on collision. Untextured
   primitives and programmer art are failures regardless of how good the driving is. Original characters and
   karts — design your own racers rather than approximating Nintendo's.

8. **Sixty locked frames per second** with all eight karts, full particles and the whole track visible. Frame
   drops during a race are the most visible failure mode on camera. Profile it and fix it.

9. **Audio, synthesized via the Web Audio API.** Engine note that tracks throttle and speed, drift-charge
   tones that step with the mini-turbo tiers, boost, impacts, item sounds, coin pickup, countdown. No
   hotlinked audio and no Nintendo music.

10. **Single self-contained `index.html`.** Any library via CDN — three.js, a physics engine, anything. No
    build step, no server, no API keys, no hotlinked sprites or textures. Generate art procedurally or author
    it in canvas/SVG/WebGL. You have free reign to look up what libraries exist and how to use them.

11. **Log every asset's license** in BUILD_NOTES.md — anything CC0/CC-BY you pulled in, and confirmation that
    nothing came from Nintendo.

12. **QA it by actually playing it.** Race several full three-lap races. Confirm all three mini-turbo tiers
    charge and pay off, the AI completes laps without getting stuck or cutting, red and blue shells track
    correctly, falling off respawns properly, coins raise speed, lap counting is correct, nothing softlocks,
    and the frame rate holds through a pack fight. Fix what breaks.