I got strangely invested in this. Very interesting concept with good art choices. The only gripe I have with the gameplay is the feeling of not making any progress. Being on round 15 feels much the same as being on round 4. I could see this being changed with buildings that can defend surrounding structures against the impending wheel of destruction, but I'm not sure if that goes against the whole randomness thing, and might feel stagnant.
Good job on making a very clean game.