This is really cute! I love the art, and the concept of the mechanic is really clever.
However, part of the screen gets cut off unless you're in fullscreen, which hides important platforms. It also would've been more intuitive to make holding things as a ghost an on/off toggle instead of having to hold down space, it took me a while to figure that out, even with the instructions on the screen. Controls are sort of fiddly too, it feels like the player character is floating/sliding. And I didn't really understand why I could fall asleep in certain points on the map, but not in others.
Overall though, I would love to see this built on. I think you came up with something really charming here!