Very clever puzzling! But not so clever that I got stuck forever on a puzzle. :)
The presentation is very nice, the UI looks great, especially the way the level selections slide across the screen when you switch from one to the next.
It wasn't always immediately obvious what any particular pressure plate had opened, usually I approached a puzzle under the assumption that I had to press down all of them as soon as they were available, which worked most of the time.
It was also unclear what the ghost could and couldn't pass through. Obviously it only takes bumping into the iron bars once to understand that a ghost can't pass through them, but it took me an embarrassingly long time to realize that the plank bridges were something I couldn't use as a ghost. I assumed I kept lining up my approach incorrectly and was going off one side or the other.
I appreciate the inclusion of a sprint button! But when in ghost mode this did once cause me to pass outside the level boundary and fall into the void.