I got softlocked by accidentally putting myself in orbit around a black hole on the third stage. I think adding a pause menu where you can undo the last hit or restart the stage would be nice...
Something to explain controls would also have been nice, since there's no way to know about the flag radar thing without reading the description. That said, this is quite good for a solo project! Nice job!
Also, I like the option to change palettes, and appreciate the ability to change the volume! And, the ball being affected by gravity is super cool!