An electrical device such as a switch includes a light source and light sensor to detect ambient light and actuate the light source when the ambient light is below a predetermined level. An electric-power supply unit converts thermal energy generated from a body temperature of a user into electric power upon the user contacting the electric-power supply unit, and supplies the electric power to the display control unit. Further provided are isolated polypeptides having 2,5-DKG permease acitivity, immunogenic peptides therefrom, and antibodies specific therefor. Because a transparent or highly translucent substrate is used for the game piece, and because the density of the ink application is controlled within specific ranges, this game piece may be used with a computer monitor, or with other low-intensity sources of additive light. They are therefore useful for the treatment, control, or prevention of diseases and disorders responsive to the activation of MC-4R, such as obesity, diabetes, sexual dysfunction, including erectile dysfunction and female sexual dysfunction. The display electrodes and the wirings respectively have a bilayer structure of a transparent conductive layer and a metal layer.