Wii U’s defining feature is a giant touchpad controller. While one player controls Samus’ spaceship, other players may have tiny touch screens of their own. A Japanese patent application filed by Nintendo reveals an accessory you slide on to a Wii remote and turns it into a touchpad.
The magic of mirrors makes the device work. When you touch the pad an infrared LED turns on and the amplified beams from the LED bounce off the mirror and are interpreted by the controller as position data. If you don’t touch the pad, the remote works just like a standard Wii remote.
Nintendo proposes their accessory can be used as an in-game drawing pad or to add a mouse pointer interface to a video game.