The design is really good, the game is pretty ! It seems a little buggy, I recommend to players to wait and don't spam click. I would have let the player unzoom or move the camera with right click and faster. ^^ The idea is interesting, and the game is entertaining !
The theme is respected, but I kind of think I'd prefer the game with more towers, so I don't think the uniqueness of the tower adds much to your gameplay.