Really nice, game, and concept, the story might not be that clear tho, as well as the transformative aspect. I like the mechanics of the game the most, its really engaging when you need to sort of figure out your way through the game. The game mechanics are hard to understand at first, since it took me a while, just to get out of the first room. I think that maybe control mapping could a bit more 'traditional'. I fell that your game, really nicely incorporates the "flow" theory, however, the story wasn't so clear.
I also managed to get the ghost to fall out of the world, and have the amulet fall with it. Then when i switched to the ghost i kept on falling indefinitely. Here's proof, that i crashed your game:
P.S. I think it would be nice if you had auditory feedback for when the guard is not stunned anymore, since sometimes you cannot see if he is anymore. Because of that i thought he was still stunned so i blindly went into his field of vision.