The controls could use some refinement, namely that spacebar is easily pressed so having it reset the game accidently is really common for me. Also having a mouse involved when you can't even see a cursor is a little weird and results in clicking off the window more often than not. A double tap in a direction to attack could be a way to remap it.
The music was a little piercing, but with some tweaking it could be enjoyable.
Bugs: When you die (in bat form?) and respawn (without using spacebar), the camera is already moving up quickly.
Overall great job. It fits the theme fairly well, though is certainly difficult game for me.