Switching tracks is with arrow keys / W A S D (i.e., D when over the dot if you're trying to move to a ring on the right). The space bar is for keeping track of the bpm. Following the orange wave will help realign the rhythm if you get out of sync. The timing is fairly tight, you have a 125ms window around the dot indicator to successfully switch. A little tip I used was falling below the bpm on purpose to slow my speed down on tricky switches, and then tapping back up again before the meter depleted. The timing can be hard, even for me after spending hours playing it -- one of my wishlist features was adding a slider to adjust the threshold but alas. Thanks for playing!