Interactive wall games turn a plain wall into a playing surface. A projector or LED wall shows the picture, and a sensor reads hands, balls or touches on it. Schools, play centres, exhibition halls and shopping centres buy them for walls that visitors pass every day. Choose by wall size, by whether you want a projector or an LED surface, and by the type of input: touch, throw or gesture. Check that the wall is flat and that the room can be dimmed if you use a projector.