Liked the music, and it really shows you put a lot of effort into this game.
Some things to consider:
The walls are a bit noisy, they take the focus from the game because there is a lot going on in the walls. Because of that, most of the games use a blank color or very little details in them!
Same thing could be said about the floor. It's more than enough to put a few fixels in order to show texture!
I would also zoom out the camera a little because when the monsters enter the screen you don't have a lot of time to react.
Well done!