I don't know exactly why, maybe it's because I love tower defense, maybe it's because the controls are so simple and clean, but I enjoyed this A LOT! :D
You basically made a tower defense but with perishable moving towers, and that's a twist on the mechanics that I've never seen. I think the core of the gameplay is incredibly solid, so now you could add more enemies and/or types of cloud!
The camera was just a bit... far away, sometimes ^^ But anyway: great game, I loved it! :)