13-second 3D giraffe bike crash animation in desert

[Note: the creator shared a partial prompt. Wording below is theirs.] GOAL: Build "Giraffe Ride" — a single self-contained HTML file (inline JS/CSS, English UI): a 13-second real-time 3D animation of a low-poly giraffe riding a long bicycle through a desert, weaving between scattered obstacles, crashing into a STOP sign and flying off. 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 except one canvas texture for the sign). 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. The giraffe: faceted body, hump and rump spheres; long neck of 4 tapered segments with a row of dark-brown blocky mane spikes along the back; head with tan muzzle, small dark eyes with a white glint, two short ossicones with dark knobs, small cone ears; pale cream lower legs, black hooves, thin tail with a dark tuft. Reticulated coat: a 3D Voronoi field (large reddish-brown cells #9a3c12–#7f2e0c separated by thick cream-yellow lines #e7b453) computed in each part's own object space plus a per-part seed, so the patches ride with the body instead of sliding. The bike: a stretched city bike with a 2.25 m wheelbase: double top tube with cross braces, long down tube, long swept-back handlebars reaching back to the rider, black tyres, cream spokes, brown saddle. Frame colour is switchable. DESERT Low-poly sand ground with per-face colour variation, flat along the ride and rising into dunes further away; sky dome gradient from blue to warm haze, matching fog; distant mesas; a faint tyre track along the path. Obstacles near the ride, not in a row: one on the inside of every swerve, so the bike visibly rides around it (saguaro, barrel cactus, rocks, oil drum, cow skull, traffic cones, dead tree, half-buried tyre), plus a few further out on alternating sides. Only low objects on the camera side, so nothing blocks the view. Lots of scattered cacti, rocks and bushes in the distance. A tumbleweed rolls across the path just ahead of the bike around t = 5.5 s. TIMELINE 0–10.4 s: the bike follows an arc-length Catmull-Rom spline that weaves between the obstacles, slowly speeding up. It leans into turns, steers, wheels roll, the crank turns; the giraffe's hind hooves stay on the pedals and front hooves on the grips through two-bone IK; slight body bob, neck sway, tail swing; small dust puffs behind the rear wheel. 10.4 s: the front wheel hits the pole of a red octagonal STOP sign (white border, "STOP" from a canvas texture, plate turned toward the camera). The bike stops dead, pitches up on its front wheel, drops back and topples onto its side; the rear wheel keeps spinning; the sign bends forward an