That was a very creative interpretation of the theme. It was also a really interesting take on a puzzle game. The music was also great.
By level 4 the mechanic started to wear on me, and by level 5 I just didn't have the motivation to try and finish the level. A second music track might've broken up the monotony a bit too. I also found that by entering ghost mode right as skeletons saw you, you could trap them and they would follow you around but not kill you.
Overall a solid game loop and good presentation.