Great game! I love tower defense games, and there are really neat ideas in this one!
I'd be cool to know beforehand the shooting pattern of towers, though. I did put my heavy tower in a place where it couldn't shoot anyone ^^ (also, blue tower would need a severe boost :)) Well, of course, a jame game cannot be fully polished.
Hope you'll update and expand this promising game!!
PS: Q and W are not the best choice when using 2 buttons, because on AZERTY and QWERTZ keyboards they are not together, but in this case that's not a big deal.