Very creative! Getting the hang of rotating the circle correctly took a bit of practice but I made it to what was probably near the end of level 2 after ~10 minutes. I almost thought it was over after the "congratulations" sound clip and the end of level 1, but I'm glad I continued because the 2nd rhythm was fun!
I found the background music to be a bit awkward--there's nothing playing on the title screen, and then there's (very nice!) music during the tutorial screens, which then cuts off upon starting the game. I see how the polyrhythms probably don't play nicely with most music, which might be the reason for nothing in the background while playing, but maybe something like an arhythmic drone track would work to fill out the sound space here. There's not a lot of sound feedback in the first moments of the game before any rhythms are playing (and I didn't understand that that's what was going to happen for a while on my first attempt while I was very bad at the game XD), so I wasn't sure if something was broken or not.
An interesting behavior that evolved out of the game mechanics was that after barely missing a colored target section a few times (which happened a lot to me early on), I ended up with death zones surrounding all of my targets, which made learning a bit unforgiving. But the panic of going for a target with no buffer on either side was also kind of exciting, so I don't think this is necessarily a bad thing depending on how you want the game to feel.
One feature I was wishing for while playing longer games was some added safety from finishing a ring quickly. If the buffer circles that weren't used in a previous ring could fall back towards the center, this would reward efficient targeting in the first rings, and less opportunity for a sudden death deeper into a run.
All in all, a very interesting and fun game! I enjoyed playing and the resulting rhythms were fun to hear unfold over several rings of targets. Great work!