This was incredibly polished. I honestly forgot I was playing a jam game for a second.
The sound design was great too. It was subtle enough to let the music shine, but still present enough to give good feedback during gameplay. The music track also fit the classic shmup vibe really well. The shrink implementation was a really cool idea and was nicely executed. I also thought it was really impressive that you were able to include and balance multiple difficulty modes for a jam game.
The boss was a big highlight too, both visually and mechanically. The art and animation looked great across the whole game, and there was a nice variety of enemies. The title screen and UI also added a lot to how polished the whole thing felt. The whole game felt very complete.