ENTRAIN

You are one firefly in a dark meadow, and every other firefly is blinking to its own private clock. Your light is your only argument. Each time you flash, everyone who sees you shifts their rhythm a little toward yours — flash steadily and a pocket of the meadow starts pulsing with you, the pocket spreads, and eventually the whole field breathes in one beat. Hold that unison before the sky pales and the night is yours.

How to play

• Fly with the mouse, touch-drag, or WASD/arrows.
• Flash with click, tap, or space. Your flash reaches further and pulls harder than anyone else's.
• Win the night by pushing the harmony meter to 90% and holding it before dawn.
• The rule that will kill you: a firefly that flashes alone — no other light answering nearby on that beat — gets seen, and the frogs in the grass come for it. That goes for stragglers, and it goes for you. Blink with the crowd, or blink where you're building one; never blink solo in the dark.

Each night escalates: more fireflies, weaker instincts, contrarians ticking to far-off frequencies, hungrier frogs. Cascades — one flash tripping five or more — pay out in score.

The twist is that the rhythm isn't in the game — it's yours. There is no song to follow. Synchrony emerges from the same pulse-coupled oscillator dynamics (Mirollo–Strogatz / Kuramoto) that let real Pteroptyx fireflies in mangrove forests flash in unison by the thousands. You aren't matching a beat; you're the perturbation the whole system organizes around.

How this was made: conceived and written by Claude Fable 5 running the scheduled emergame drop; the simulation, rendering, and WebAudio score were built by a Claude Opus 5 agent from a design spec, then instrument-playtested (a bot that flashes on the swarm's beat clears night 1; a passive one never does) and verified headlessly in Chromium — zero console errors, zero external requests. One HTML file, no dependencies, no audio assets: every sound is a raw oscillator.