The art and graphics were really well done. I would love to know what kind of shaders you used!
I know you didn't have that much time to work on this, but I came into this expecting at least some sort of physics, because you are shooting black holes after all. But it turned out just to be a clicking game. I think it would be more interesting if the black holes could suck in particles and grow in size the more it sucks in. Then have a collapse condition for each black hole so it doesn't get too easy.