Please add in a tutorial or something to show what the little smiley face thingy does, the health and money ones are self-explanatory, but I can't figure out what that one does. Also, if we could be able to see the stats of the towers, that would help a lot >_>.
But good game! I was thinking the other week of how a game like this would be fun.
Very VERY VERY VERY VERY VERY frustrating. Some of the levels make it seem like you want the player to bash the computer out of anger. The glitches don't help either. It was a nice concept, but it was less of a drawing game than timing game. If you make another, make it a bit easier and less tedious and glitchy.
I think it's pretty good, maybe make the graphics a bit more detailed/flashy, add some different enemies, and maybe some other upgrades for your ship. And I don't know if you have a boss in it or not, since I didn't get too far, but add a few bosses or mini-bosses too perhaps.