Note to self, don't try and play mouse based games on a trackpad :P Despite my control handicap I managed to last a pretty decent amount of time, largely because of the very generous galaxy changing that I could use to get out of a sticky situation. It's a neat idea, being able to switch between different galaxies when things get to hairy, but I think it might make sense to tie the scoring to kills, or maybe add some sort of score penalty to switching galaxies. Basically, some sort of incentive to not constantly switch galaxies to avoid having to deal with any of the hazards.
I really liked the work you put into the animated sprites for all of the characters and hazards, I think it really gives a good feel to your game. I especially liked the green eyeball alien, that animation was definitely my favourite.