Touch: tap anywhere to flip gravity to the other rail; tap to start and to play again; tap the pause and sound buttons at the top right · Keyboard: Space, Up, W, K or Enter to flip (and to start / retry); P or Esc to pause; M to mute. With a mouse, click anywhere to flip.
About:
A one-button gravity runner, drawn and synthesised entirely in code with no image or audio files. You are a spark skating along the inside and outside of a long orbital ribbon that is slowly breaking up. Gravity only ever pulls you to one of two rails, the near one or the far one, and your single input flips it: tap, press Space or Up, or click anywhere, and the spark arcs across the gap to the other rail. There is nothing else to learn.
The ribbon throws three kinds of trouble at you and every one is telegraphed before it arrives. Shard clusters jut out from a rail, so you must be on the other side when you reach them. Voids are breaks in a rail you have to be away from, or you fall through. Pillars bridge the whole ribbon with a single safe side, and some of them force a flip whether you like it or not. Each hazard glows and pulses as it comes into range, so a clear head always has time to choose. Clearing one feeds a combo, and the combo lifts a score multiplier up to eight; forced-flip and pillar passes are worth more. Scattered light cells between the hazards are optional risk for extra points, and shaving past a shard without touching it reads as a near miss.
The simulation runs at a fixed step, so the same seed always plays out the same way, and the whole track is generated to be provably clearable at the speed you are travelling. Speed climbs the further you get, which tightens every decision. A run ends the instant you clip a hazard or miss a rail, the ribbon blows apart, and a single tap starts a fresh run right away. There is no menu to wade back through. It plays in any orientation but opens up on a wide screen; on a tall phone a hint suggests turning sideways for more room to read what is coming.
Credits:
Made by Leetdom, 2026. Written for Leetdom, and it lives here.
Phone check: 2026-10-03: built and tested by the remake-60 build agent. All sound and art are generated in code, no asset files. A node bot runs core.js unchanged and checks determinism (same seed plus same flips reproduces the trace exactly), solvability (the built-in solver survives 0 deaths over 2400 lanes across 300 seeds), invariants (no NaN, the spark stays between the rails, speed is monotonic, the multiplier stays within 1..8), the flip physics (one flip crosses to the far rail in 0.304 s), and a human reaction model (a jittery 0.17 s player always clears the opening and a sharper 0.11 s player reaches much further). Real CDP input drove a headless Chromium build: on a 1280x720 desktop Space starts and keyboard flips reach the sim and the score climbs; a death leads to a one-tap retry with a short guard so the death tap does not instantly restart; the pause button and a hidden tab both pause; a mid-run resize to a 760x1000 portrait at 2x keeps the run alive and the canvas backing store tracks size times device pixel ratio; with localStorage throwing the game still boots and plays and records no console errors; a 390x844 portrait phone and an 844x390 landscape phone both start and flip on touch. Zero console errors and zero external or network requests across every scenario. The audio mix was rendered offline through the game's own sound code: with every sound stacked at once the peak is -4.9 dBFS (full-mix peak -4.0 dBFS), music sits about 20 dB under a loud effect and about 10 dB under on overall RMS, there is true silence between sounds (700 ms clear gaps, silent tail after the crash), the music breathes rather than drones (58 of 132 windows near-silent in the arp and pad gaps), and above 6 kHz is only a fast-rolling-off transient shoulder (-64 dBFS by 8 kHz, -74 dBFS by 10 kHz) with nothing harsh sustained.
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