GNOMON

GNOMON is a top-down arcade game about real-time shadow geometry. A sun crosses the sky over each ~80-second day, and every standing stone on the plaza casts a true shadow — computed from the sun's actual azimuth and elevation — that sweeps, stretches, and shrinks as the day turns. Shade is the only safe ground, and it never stops moving.

How to play

• Move with WASD / arrows, hold the mouse, or drag a finger — all three work.
• Shadow cools you. Open sunlight fills your scorch meter. Fill it completely and you burst into embers.
• Each day, five sun-shards crystallise out of the exposed stone, one at a time — usually somewhere uncomfortably sunny. Take all five and the gate opens. Slip through before dusk for a time bonus; get caught by nightfall and the day still ends, just cheaper.
• P pauses, M mutes, and the game keeps going as long as you do — every day the sun moves faster and burns hotter.

The twist

Noon. Twice-daily long shadows lull you into wandering; then the sun climbs, and every shadow on the plaza shrinks to a sliver at once. The horizon arc at the top of the screen shows exactly where the sun is — plan to be near a big stone when the NOON warning pulses, or you won't be near anything at all. From day 2, drifting cloud-shadows cross the plaza: mobile cover, if you can keep up with it.

How it was made

This run: the concept, name, and all of this text came from Claude Fable 5; the game itself was built in a single pass by a Claude Opus 5 agent as one self-contained HTML file — no libraries, no assets, all sound synthesized live with WebAudio oscillators. The shade test is exact point-in-capsule geometry, not pixel sampling. Fairness was measured rather than guessed: the layout generator guarantees that at high noon no point on the plaza is more than about 1.2 seconds of travel from full shade, and a scripted player survived day 1 in 30 of 30 runs before we shipped. Verified in headless Chromium — start, play, noon, death, restart, resize — with zero console errors.