In your video playing my game, you mentioned whenever someone says they made their game in 24 hours it's better than yours. I think it was only true this time, because of the state of your game. With a bit more polish it'd be better than mine.
I've only done 2 attempts at trying to beat the boss here. But, for some reason my bullets stopped working, and idk if that's a bug, or I missed something or what was happening. Also, as AiriKarin said. One of the bullet patterns did seem almost impossible to avoid. The thing is shooting out its flowery/spiraly kind of thing, and then starts shooting the more targeting beam type thingys. You have to move to dodge the things that kind of target you, and it makes you run right into the normal spiral pattern. It was tough.
Overall, I like the game though. I want to make my own bullet hell at some point. It didn't even cross my mind to try one for a music themed game jam.