Nice game! A couple suggestions I have is to let people left click to shoot instead of space and to make big enemies faster and small enemies slower, since as it is big enemies are always the weakest, they are the easiest to kill and the slowest, while small enemies are always the strongest, hardest to kill and fastest. Also, there is a glitch where the pits can be walked over as medium size if you were big and then finished a level or died.