Well instead of defending you attack in a tower defense game. It's wasn't strictly specified that a mechanic has to be missing from the game.
I know it's really easy to play, I didn't really have time to tweak the gameplay, but that's what happens when the idea is big and the time is short. I'm happy that at least it's playable :P
Thanks for the feedbeck it's good to know that it's not exactly clear how the game fits the theme.