An amazing quality even if it was a full game, let alone the demo. Only two things I could mention as something I'd like to see changed/looked at (unless its already done):
Witch coins at the end of the Haunted Hall are extremely laggy on pick up. Not sure about single ones, but final room is pretty bad in that regard for some reason:)
During the scenes, when modifier is reached and applied, its text goes right into your notes hit zone, which is pretty distracting sometimes. Not sure how exactly it can be changed but would be nice if it changes somehow:)
Thanks for your job and good luck with full version release!