Nine games about noticing things. Afterimage shows you five colours, one at a time, then asks you to rebuild each on a slider. Sine Language plays five tones and sends you to find them again by ear. Second Sense asks you to hold a button for exactly as long as the interval you just heard — no clock anywhere. The others work rhythm, spatial memory and melody the same way: see it or hear it, then dial it back in from memory. You will be worse at them than you expect, and that is most of the fun.
The site is played by ear, so sound is a first-class citizen: every tone, tick and beat is synthesised live in the Web Audio API — nothing is a sample, nothing is loaded at runtime. Beat Lab takes the same synth engine and turns it into a small browser studio, where you can build a loop and download the result.
Each day seeds one shared challenge, and daily scores go to the arcade leaderboard — where the server rebuilds the day’s challenge from the same seed and re-scores your answers before believing a number. Like everything here it was built with an AI pair, with every line reviewed, and it works with the network off.