Tide.day
Oct 6, 2026 — A daily sandcastle game. Build on today's beach for 90 seconds, then watch a real simulated tide take your castle. Your score is how long the keep stays dry.
Tide.day gives everyone the same beach, the same waves and the same bucket of sand each day. You get 90 seconds to build inside a staked plot: drag to pile sand, dig a moat (every scoop goes back in the bucket), pat the walls hard and drop bucket towers on top. Then the tide comes in, wave by wave, with a big set every forty seconds or so and one rogue wave. Your score is how long the top of your keep stays dry, against a par set by a plain scripted castle on the same beach.
Nothing in it is animated. The beach is a 96 × 128 heightfield of 5 cm cells. The water runs over it as shallow water (virtual pipes at 60 steps a second), fast thin water picks up sand and drops it where it slows, and any slope steeper than the sand can hold slides. Wet sand holds far less than dry, and patted sand far more, so walls fall from the foot up, and a moat buys time until it fills. Each day also brings one beach find: a driftwood plank, shells, seaweed or a big bucket.
The sim uses only plain arithmetic and a seeded random number generator, so a castle's tape (every touch, about 1–2 KB) replays to the identical fall in any browser. The share link carries it, and when your keep goes under you get a 10-second time-lapse of the whole tide.
The idea came from the studio's own pitch, out of some research into liquids in three.js. The promo above was rendered from the real simulation, replaying a scripted castle on beach #1. It's built with three.js, and every sound is synthesized.