Sort of impressive?
I was having great fun until I hit level six, where I realized that the enemies don't have physics. Or rather, that gravity is not observed with the physics (properly). If a circle lands on a slope, it should roll. I kept going for a while, but each and every time I set down a bomb I think "Will the physics end up screwing this shot up?" The answer is nearly always yes, and it sort of dissapoints me.
One thing you could do, however, would be to make the enemies squares, rather than circles, which would help explain the gigantic amount of friction these little guys carry. I guess I'm just one of those guys that likes to see a game that has proper physics, or at the very least explains improper ones.
All in all, I'd call this a diamond in the rough. Spend maybe a week or two working on the physics, and I'd gladly give this a nine-But until then, I'm going to hafta give you a six. Keep making games!