I made a Pebble watch face: Hearth shows the time as four big digits, and the digits are windows onto a live fire.
It’s inspired by Yuri Galanter’s Fireplace, which plays recorded flames through the time. Hearth computes its flames on the watch instead, with the classic PSX Doom fire: ten lines of code that turn a row of heat into rising, flickering flames.
That tiny algorithm is so simple and efficient (about a millisecond of work per frame, ten to forty times less than playing back recorded flames) that there’s room to let the fire respond to the world. The colder it is outside, the higher the flames burn. They burn low during the day and high at night, rising at sunset. They lean with the local wind or when you tilt your wrist, and leap up when you tap the watch. On the Pebble Time 2 and 2 Duo you can hear it too: every crackle is synthesized on the spot, so no two sound alike.
It runs on every Pebble, from the original to the Round 2. The code is MIT-licensed on GitHub, and Hearth is available on the Pebble app store.