Planet in a bottle is basically a Tamagotchi (i.e.a virtual pet) where you periodically check on your minions on a planet and try to keep their balance of water and sun at an optimal, and give them a periodic "nudge" to let them know you are there. If you keep the optimal balance, they will grow faster and be happier.
The game keeps track of how often is your attention and will "react" accordingly.
It is somewhat amusing... for a day or two. Then you realize unless you check in every few hours your population will not prosper, and that's just too demanding.
Rating: try it