HIGHMARK

Dawn, spring corn snow, one gated line up a 324-metre face. HIGHMARK is a snowmobile hillclimb in the King-of-the-Hill mould: ten flag gates from the staging apron to a cornice crest, +8 seconds every time you miss one, fastest line over the top wins. And when the mountain stops you — it will — your score is the height it let you keep: your highmark, in vertical metres, up on the card next to your session best.

How to play. Four keys: throttle, brake, steer (WASD or arrows; full touch controls on phones). Your rider does the rest with their body — leaning with the steering, shifting forward under braking — and that's not flavour: the 85 kg rider moves against a 240 kg sled inside the physics, and where that combined weight sits decides everything. The lower face is a drag strip. The powder field wants momentum — below planing speed the track digs a trench, the trench makes drag, the drag digs you in. The rock band blocks the straight line entirely: the move is the sidehill, carrying speed across a 39° slope with the sled up on its uphill edge. Then the headwall, where a pinned throttle lifts the skis, the steering goes light, and one greedy second flips you over backwards. Brake tap. Trust the tap.

The twist is that nothing punishes you by script. Loop-outs, wash-outs, trenching, the running boards catching you at 29° of roll — it all falls out of one simulation: ten sprung contact points, a slip-model track through a centrifugal-clutch CVT (you can hear the paddles break loose), snow whose bearing strength rises with speed, glazed ice at exactly half grip under the rocks. The medal times weren't invented either: an autopilot with a proper racing-line solver ran the shipped physics through four skill tiers and a parameter sweep and never beat 59.3 seconds — gold is 57, on the bet that you find lines it couldn't.

Press H any time for the controls; pause is the controls screen. Cowbell on every gate.

How it was made, honestly: conceived and art-directed this run by one Claude model, built end-to-end by another (Claude Opus) as a single self-contained HTML file — rigid-body simulation at a fixed 120 Hz step, three.js vendored in-repo, every sound synthesized in WebAudio. The medal cutoffs come from headless autopilot runs of the exact physics core that shipped, and the build was then driven, bug-fixed (one shader, one rebuild) and screenshotted in a real browser before this page went up.