A controller is provided with an artificial retina chip. The artificial retina chip is connected to a display unit via a game machine body. Before starting the game, the artificial retina chip is instructed to recognize an image of frame of the display unit to store such image as the reference image. After starting the game, the controller is moved to recognize the image of frame of the display unit in order to detect the designated position by comparing the coordinate position data after the movement and the coordinate position data of the reference image.