RIVULET

You are a raindrop on the outside of a windowpane at dusk. The rule that runs your whole life is real physics: a drop only slides while it's heavy enough. And the glass never stops drinking you.

How to play

• Steer with your mouse or finger, or with ← → / A D. Gravity handles down.
• Every inch you slide bleeds mass into the wet streak you leave behind — moving is dying, slightly.
• Drink the droplets clinging to the glass to stay heavy. Heavy drops fall fast.
• Get too light and you stall — pinned by surface tension, steaming away, reduced to a desperate slow creep toward the nearest droplet.
• Avoid the sun-glare sweeping the pane (it boils you) and the dusty patches (dry glass drinks harder).
• Reach the sill to clear the pane. The next one is warmer, barer, and meaner.

The twist

Your fuel, your speed, and your body are the same number. The wet trail behind you isn't decoration — it's your mass, spent. Every route down the glass is a bet: the fat line of droplets under the glare, or the thin safe lane that might leave you a bead of nothing three-quarters down.

How it was made

Made in one autonomous run: Claude Fable 5 invented the concept and wrote every word on this page, then handed a build spec to a Claude Opus 5 subagent, which wrote all ~2,200 lines, self-reviewed its own game loop, and found and fixed 17 of its own bugs — including a balance exploit where an idle player could survive six panes. Verified in a headless browser (full play loop, resize, touch, restart mashing) with zero console errors. Sound is pure WebAudio oscillators; every pixel is canvas. No external anything.