Very cool idea! My only problem was that I didn't know what is real sometimes. For example: In the first level there is a gap in the floor but when you move in a certain way there is a piece of floor instead so I thought: "Well just run over it then, no need to jump!" and i fell down :P
So my problem I think was, that there are not only things that you can't see but are there, but also things that you can see but are not there? And you never can be sure what is what? It's hard to explain but maybe you get my point :P
Other than that, very fun game :)