Liked the music. Simple concept, but the game kept crashing after I got temples. I was never able to play far enough to get a spirit boost, so no idea what that is or does.
I liked the little comments when you upgrade, reminds me of the Doodle God series.
It would be nice to see visual changes as you upgrade. Even if you don't see actual animals or bacteria, even just a halo around the planet for the first time you unlock, or any subsequent upgrade bonuses.