Thanks for criticism.
Yes, I was thinking about music, but when I was browsing OpenGameArt for music (I was too lazy to write my own), imho there was some garbage (Disclaimer: I respect the authors' work) with a CC0 license. I didn't feel like scrolling through a long list, so I chose the only thing that sounded good and wouldn't trigger a DMCA violation.
Regarding the collisions, I don't even know why it happened, but on the last day of the jam, everything broke 😭, and that's why so many strange bugs appeared. I'd really like to fix these bugs, but I don't know what caused them. Long story short, I'm burned out and, unfortunately, I've lost all desire to create games. 😪