The Line.

Your beats are the levels. In the DJ studio, make a pattern and press Play it in The Line, or press SHARE and paste the link here. The loop plays as a song that builds: kick and snare, then the hats, then everything. The notes are exactly what you hear, in four lanes, and the sounds are made in your browser with the studio's own voices.

Kept on this phone. Your best scores and timing setting stay in this browser. A finished song counts in Play. A challenge link carries the beat itself, so anybody can play the same song.