I enjoyed it, the atmosphere is relaxing and a tiny bit ominous. I played a few times to get things right, it wasn't hard once you get the hang of things but I still had to fiddle around a little.
Only thing I was a bit disappointed about is that the planets' stats are frozen after the win, so even if I choose to look around and I plant more trees, I can't finish fixing the atmosphere 100%. Also it would be good to be able to sell structures, since mis-clicking happens. And, it would be nice to have difficulty levels where planets are harder to balance and/or timer is shorter, for replayability.
Very nice little game, I'd definitely be happy if a more fleshed out version was in the works. This concept with those mechanics is a combo with great potential, it could totally be used as the basis for a quite complex game.