Very well executed tower defense. Some of the mechanics are so wide reaching that you'll almost never see them (I'm looking at you, mega-mega tower thing). Very cool mix of levels, ranging from easy to super hard. My only complaint is the inclusion of juggling as a core mechanic.
A step back from the original. By requiring a double upgrade in every level, the game has essentially the same pacing in every stage, instead of actually allowing upgrades to change the feel of a level, the just extend it. Poor design choices hurt this one pretty badly.