It's cute, and the engine works like I guess it should (simple concept + good design = win), but I don't know that I'd call it good. It seems that it'd be difficult to sustain the concept for more levels without some new element like a larger playfield or different gravitational pulls.
Not a bad concept or game, but it suffers somewhat from being an unreleasable beta version. I imagine when the actual game comes out it will be quite good.
I understand the allure and mood of the game, but I'm not sure I know enough words to express how tired I am of featureless figures with guns in a black, white, and red setting. There has to be some other type of game in the world.