Hey, it’s nice! I wish the calibration step was clearer though: it says you can “join in anytime” but in fact, you need to repeat the beats a certain number of times to complete the calibration. So I was looking for a secret button to join or anything (but then it wouldn’t really be one-button).
Maybe showing a number of calibration beats left would be better. Also a hint that you should enable audio (I had mine shut down), and visual indication of the beat too. Fortunately there is at least the the disc rotating so I could evaluate the beat period, but I certainly had an offset to the actual beat.
Maybe this is already done in the Steam version? If so, and you don’t want to spend time upgrading the free version, you could just add instructions on the itch page.