Space to shoot, A and D to tilt left or right, Q and E to rotate weapon. Weapons unlock after waves at a fixed interval. Shoot all the enemies and don't let any leak by or you lose lives. If you run out of lives, it's game over.
This game was made for a local day of hack, but also for Ludum Dare 43, theme "sacrifices must be made." I don't think I even bothered to try to shoehorn the theme in. I am very happy with the end result of this game. It looks quite aesthetically pleasing and has a simple but fun mechanic.