Nice idea and cool visuals but in this isometric type of perspective it is sometimes hard to interpret were something is located in 3D space.
I'm not sure if it is a bug but sometimes nothing happens when I try to go into ghost mode. If the time you can stay in ghost mode and the time it is possible to go into ghost mode are limited you must signal this to the player.
It would also be good if the player had (automatic) checkpoints for every room