Fru is a Kinect based game that was made in 48 hours during the Global Game Jam. To understand the concept, you'd have to imagine a game represented by two pieces of paper, each one representing a level. One piece of paper is placed on top of the other, therefore in a normal game you'd only see the top level.
However, Fru utilises the player's shape outline to carve a hole in the first piece of paper, revealing the second piece of paper beneath. This way players can utilises the two levels at once to solve puzzles and come up with creative solutions.