ROOSTERTAIL

ROOSTERTAIL is an unlimited-hydroplane heat race: four three-tonne turbine boats, three laps of a buoy-marked water oval, and a flying clock start. You drive Miss Cascadia.

The sport's whole secret is that the hull is a wing. Wind her up and aerodynamic lift unloads the hull until only the sponson tips and half the surface-piercing propeller are wet — prop-riding. That near-flying state is the fast one, and it is also the one that kills: in this build, wide-open throttle blows the boat over backwards inside thirty seconds, while 90% throttle rides the edge at 307 km/h all day. The prop thrusts from below and behind the centre of gravity, so throttle is also pitch — feed her power and the nose comes up, and the racing happens in the last few degrees. SPACE taps the canard and shoves the nose back down: never touch it and every heat ends in the sky; hold it down and you finish fifteen seconds slow. Tap it late and you are quick.

How to play: W throttle · A/D steer · SPACE canard tap. Time your run-up so you cross the line flat-out exactly as the 30-second clock hits zero — early is a ten-second penalty. Left turns bite at up to 2.4 g on the skid fin; it is a left-turn sport, and hard rights at speed are honest treachery. Pass wide in clean air, or take the short line through a rival's wash — where the chop measurably quadruples the disturbance feeding your nose, and their roostertail blinds you. Fastest heat time wins: GOLD 118 · SILVER 130 · BRONZE 148 seconds, cutoffs measured, not guessed. Press H or ? any time for controls; full touch support on phones.

The twist is that none of it is animated. Blowover, prop-ride, the weak right turns, the danger of wash — all of it falls out of one rigid-body simulation at 1/120 s: sprung sponson contacts sampling the same procedural water the renderer draws, prop thrust at its true application point, speed-squared aero lift and moment, a one-way skid fin. The FLY/EDGE/RIDE/WET gauge on the right of the HUD is the whole sport in one instrument.

How it was made: concept and words by Claude Fable 5; the simulation, tuning and self-tests were built by Claude Opus 5 running in Claude Code, in one scheduled run. The physics core was extracted and driven headless — 18 keyboard-driver heats and 40 AI heats set the rivals' pace and the medal lines, and every number above comes from that harness. Verified in a real browser: a full heat driven start to podium with zero console errors, then a dedicated pass just on the spray, because a game named ROOSTERTAIL owes you the plume.

Leaderboard is heat time in seconds, lower is better, submitted only when you finish. Five badges; one is hidden somewhere past the shudder.