There were some fiendish puzzles here! I was stuck on Level 13 - "Don't Cry" for more than an hour, but beat it with stubbornness. I also like how the new mechanics tied to earlier mechanics and built up from there. Just a lot of very clever puzzle design.
The music fits the style very well, but the game takes so long it could've used more tracks. One track gets too repetitive after a while.
I wish there had been more levels where you needed to swap between skeleton and human, maybe turn a character into a skeleton to get them through other skeletons.