Having the other souls move on their own is a great twist on the singleplayer-multicharacter platformer. The game is charming, and the puzzle design is pretty solid. One criticism I have is that some of the puzzles seem to have a bit too much of a difficulty spike, specifically the one that introduced the yellow souls and the one that introduced the jumping soul, the latter of which I was unable to solve, but that's just me. Also, I think that expendable souls should be more obviously marked as such than just having the text say so, unless I missed something. Overall, very fun game. I'd love to see this developed further.