Hey!
I'll focus on constructive criticism in my comment, but that doesn't mean I don't agree with the others in the section about the pros, especially the art.
Notes:
There is a minor visual glitch when the first boss exits his ball state, for a moment, the ball sprite appears where he had started.
Personal opinion (what I felt as a player, and each player is different):
1. I saw you can climb over the first boss with the dash, but being able to dash through him would speed up the fight a lot in my opinion. I found myself hitting and running a lot.
2. If the second boss corners you with one of those beams, and appears next to you, you'll pretty much lose a whole lot of your health or die. You can negate that by avoiding the corners, but it would be nice if there was a way to escape getting stuck like that.