Really enjoyed this one. No real criticism except maybe I'd like a help section with some stuff explained, but then again, part of the charm is buying upgrades and seeing exactly what they do. Made it to level 8 so far, without using the special at all; somehow slipped my mind and I've just noticed :D.
Great take on the theme, no doubt. Chosen music was inobtrusive and pleasant. Would probably play nice on a gamepad.
I'm off to see if I can beat the boss! :D