A sleep mode system for an electronic device can include a light source, a sensor, and a light altering component. The light altering component can rotate with one device component, such as a laptop lid, while the light source and/or sensor remain stationary with another device component, such as a laptop base. A controller can determine the orientation angle of the light altering component based on the detected light, and can put the device into or remove the device from a sleep mode based on the angle, which can reflect an open state or closed state for the electronic device.