A desktop UI check using browser automation, so please exclude this from human first-time-player and replay counts.
The opening screen gives a clear action, TAP TO SWITCH TRACKS. After PLAY, a Space input on Level 1 produced OUT OF SYNC while the pulse continued moving. That message tells us the input failed, but does not distinguish an early/late press from choosing the wrong route. Briefly highlighting the junction that currently accepts input, plus an early/late cue when appropriate, could make the next attempt more deliberate without adding a long tutorial.
This check did not complete the first level, so it supplies no useful human replay observation. The concrete suggestion is about making that first failed input easier to diagnose.