This is so good! Using mouse motion as a control scheme is particularly genius - how did no one think of this before? I particularly like the points where the mouse control is taken away from you, i.e. when you float downstream, or when you go down a slide. It's also particularly genius how the mouse can 'teleport' around the screen (i.e. when you go into a door and come out somewhere else).

This idea could even be taken further - it would be really cool to have terrain that is more difficult to traverse. I'm also intrigued by the lack of walls. I think something like a hedge maze would be really fun!