Do not read into the tower defense part. This is strictly a puzzle/action game. You also are locked into using your keyboard for movement and using your abilities. Perhaps there is controller support, but definitely no mouse. You use arrow keys for movement, z and x for activation.
All you do is pull blocks to solve levels through either moving blocks into enemies, or combining them to make your turrets/towers. THAT is your tower defense part of the game, but it's honestly not enough like an actual tower defense game to deserve that comparison.
I personally wasn't that taken by the game, but I can see where others might have an amusing time with it. Only certain puzzle games work for me, and this isn't one of them. It also requires a bit too much in the way of perfect timing, and quick reflexes, in a bothersome control scheme, from what I would think most puzzle buffs would prefer.