I really like the way you introduced the boss fights by having the music play a more action oriented part of the track. It felt very dynamic and I thought it added a lot to the game!
One of my favorite parts of this game probably is the hit stop effect when you hit an enemy. It is very responsive and the blue and purple effect along with the change in screen brightness makes for extremely clear feedback. Great job on that!
This is a minor issue, but I think the object that checks if you've fallen to your death could have been higher. When you fall off a cliff sometimes you can see the bottom of the platforms and that's a bit odd.
The menu UI is great. I really like the way it moves onto the screen instead of suddenly appearing.
The gameplay is really really fun! Overall, I thought this game was amazing.