Love the soundtrack! You might want to run the audio in a separate thread though, every time a new track is loaded the game freezes for a while.
The powerups are the evolution part? Could be more prevalent, though it was a hard theme.
Also, there should probably be a way to disable powerups, on some levels the explosive bullets are more of a punishment than a powerup, e.g. Thinking Diagonally can't be finished with them.
Have the gold award time limits been tested to be possible? :D :D I tried to get one for ages but no luck.
Either way, overall it's a very complete game, much of content and finishing touches. I liked it!