Real-time 3D horse race with jumps and a cinematic crash

[Note: the creator shared a partial prompt. Wording below is theirs.] GOAL: Build "Horse Run" — a single self-contained HTML file (inline JS/CSS, English UI): a 13-second real-time 3D animation of an articulated low-poly toy horse galloping along a desert race track, jumping over hurdles and swerving around obstacles, filmed like an endless-runner game from behind and to the side; at the end it fails the biggest jump and crashes in an epic, cinematic tumble. No titles, captions or text overlays on the page: only the full-screen 3D scene and one menu card. MOTION: TECH three.js r160 as an ES module from https://t.co/jyIKTZ7Lsd (no addons, no models, no textures). WebGL 2; if unavailable, show a fallback card. The whole animation is a pure function of time t in [0, 13] s, so the timeline can be scrubbed both ways and every frame is repeatable. STYLE Clean stylized low-poly 3D: flat-shaded matte faceted surfaces, sRGB output, no tone mapping, soft PCF shadows from a warm sun that follows the action, hemisphere sky/sand fill. Palette: sky dome top #8cc8ef, middle #cfe6f2, horizon #f4dcb2 with matching fog; HemisphereLight #dff0ff / #e2b277 at 1.25; sun #fff0d4 at 2.1; sand faces mixed from #efd3a2, #e3bd86, #f5e0b8; mesas #d99a68; rocks #b48a66 / #9c765a; cacti #5c9a4b / #4b8640; wood #9a7a5c; dust #f2dfba; stars #ffd23d. THE HORSE An articulated toy horse, like a hand-made wooden or plastic figure with visible joints: separate body sections, a segmented neck, a long head, and long legs split into parts with visible round joints at the shoulders, knees, hocks and fetlocks, and dark hooves. A mane and a long tail made of many separate strands that fly and trail with the motion. Real racehorse proportions: a long athletic body, deep chest, long arched neck, long slim legs. How you build and style it is up to you; make it striking and full of character. A procedural, IK-driven 4-beat gallop with real horse leg mechanics: legs reach, plant, push and fold, the body pitches and the neck bobs. Coat colour is switchable; mane, tail and hooves stay dark. A red saddle cloth with a white number "7" (canvas texture). DESERT RACE TRACK A wide sandy track running away into the distance with gentle curves, bordered by low white wooden rails; low-poly sand ground with per-face colour variation, rising into dunes further away; distant mesas and rock spires fading into the haze; scattered cacti, rocks and dry bushes outside the rails; a few tumbleweeds; hoof prints and dust puffs at every hoof strike. Obstacles on the track, never in a straight row, alternating sides: low wooden hurdles and rectangular hay-bale jumps it leaps over; barrels, a cow skull, rocks and cones it swerves around along a smooth spline (leaning into turns). At the end the final jump: a tall red-and-white striped fence of three rails on two posts, clearly taller than all the others. TIMELINE 0–10 s: the horse gallops, speeding up slightly. Every hurdle is ONE clean jump: a single take-off from the hind legs about one body length before it, one smooth parabolic arc (