Observing from an isometric perspective, your fundamental purpose is to guide the main character through an environment so that he can reach his target destination. This is accomplished by either manipulating physical objects in the world or by interacting with sound, light and other subliminal elements that will affect the perception of the character and his behavior within the environment.
These manipulations will both physically and mentally unlock the pathway between the starting point of the main character and his final destination.
Teaser trailer: http://www.youtube.com/watch?feature=player_embedded&v=ywyTioSJFNI
Demo footage: http://www.youtube.com/watch?v=WIJQfCFn9X4