A head-mounted display (HMD) system includes an HMD device wearable upon a head of a user, and a peripheral device that is dockable with the HMD device. The peripheral device comprises a plurality of light source elements disposed along a perimeter of a face of the peripheral device and a peripheral electronic control system. The peripheral electronic control system is configured to form an optically detectable light pattern with the plurality of light source elements by controlling each of the light source elements. The HMD device is configured to detect the optically detectable light pattern with a camera and to display an augmented reality (AR) content based on the identified optically detectable light pattern.