The music is awesome, super dynamic, and the art is simple but really stylish.
The difficulty, though, jumps way too fast. The first few waves I can just chill at the bottom and do nothing, and then it suddenly gets real once the spinning enemies show up. The boss fight feels way too tough, too. It'd be way nicer if you could just restart the level after dying instead of going all the way back to the start.
Still, really fun, great job!