What an underrated entry!
This is really nice, the music is awesome, the sprites, while basic, are enhanced by a nice use of lighting and particles. The graphics would be even better if there weren't any mixels(mixed size pixels).
The gameplay is pretty fun and I loved the coop parts (although I played it alone). The maps is also surprisingly big.
I think this deserves, more attention, maybe add some screenshots/gifs to the page?
Anyway, well done!