It was a generic defense game right up until the fourth level when you threw me a real curveball: the airborne enemy that hung out above the arc of my boulder throw, thus leaving me completely unable to hit it, thus causing me to slowly bleed health while my retarded brawny hero stood there uselessly. That's the kind of originality that makes a game stand out!
For all of that long power bar, if you go over 1/5 to 1/4, the thing fires out in an almost perfectly straight line. I don't know if that was a design choice, but it's pretty damn annoying to have a scale with such incredibly coarse granularity.