Nice idea, not sure about execution...
I like the concept and the graphics (with one or two exceptions but I'll get to that) but theres a few things that concerned me...
The upgrade menu is a little confusing... could you seperate the price? Like move it to the other side of the buy button?
The upgrades don't actually appear to do much :S
When rubbing against the sides of the screen, the screen shakes and its a bit... odd? Especially since it did the same thing when I lost a life so it confused me too...
I really liked the game, don't get me wrong. I just found these few things to annoy me a little :)