Very cool! Although I couldn't get very far, and the controls were difficult to understand at first. The idea of building a 3d maze for tower defense is compelling and interesting. The fade in and out of the interface could be a lot quicker. I can tell a lot of thought went into the underlaying mechanisms of the game - pathfinding, 3d tiles, and saving sessions between play.
I had fun trying to make a path 2 tiles up with turrets on top that worked kinda well. Those evil wheels were forced to climb a big staircase to get their precious flag.