I have mixed thoughts on this game. On one hand it's an addicting little pass time where the only real goal is the personal challenge to go as far as possible. On the other hand, it became very boring very quickly. It was really cool to watch the world start to form as the various upgrades were obtained in greater quantities, and the little phrases with each upgrade were usually fairly funny. Both quickly grow old though as there isn't enough variety or new changes after the first little while.
As I write this review I'm sitting on a base Spirit/sec of 5 quadrillion. I have at least 3k of each upgrade for the first planet and at least 1k on all but the last three upgrades (lowest is 150) on the second planet. Unfortunately there is no real end in sight, and for a game that offers so little variety over an extended period of play, that's a real shame. I enjoyed it for what it was, but I wouldn't play it again.