This is my favourite game from the jam so far! I'd absolutely love to see a full fledged game like this with trippy visuals and music, and you do a great job at selling the concept.
Syncing visuals with music is always extremely satisfying in games, and it works perfectly here. I think a one hit system allows the game to be difficult while still fair, and you appreciate the music more. However, I do think there should be checkpoints between levels, as you feel you learn a level quite well if you are able to beat it once.
I love that each level has a specific theme with it's own enemy variety, and the circle filling in the centre is a smart way of indicating level progress without the need for UI.
As I said already, I'd love to see an expanded version of this game bemuse its such a great concept, with even crazier visuals outside of the circle. Great job, definitely going to be one of my favourites from the jam!
edit: some minor things just because I like the game so much and want to give as much feedback as I can. Some projectiles pop out very suddenly which is a bit jarring, it would be better if they went off screen or faded out, but I understand they might disappear to improve performance. Secondly, I'm not sure if its web unity doing this, but the art looks compressed in some places. In the future an option for controlling the character with the mouse would be nice, as the player would be able to respond better with 360 degree movement. These are really minor things and they didn't affect my enjoyment at all, just some things I've noticed.