Abstract: A wrist device includes a curved body arranged to fit the wrist device around a user's wrist, an activity tracker circuitry configured to measure physical activity of the user of the wrist device, a processing circuitry configured to acquire physical activity-related measurement data from the activity tracker circuitry and to process the physical activity-related measurement data into physical activity-related metric characterizing the physical activity of the user, and a user interface element configured to display the physical activity-related metric. The user interface element includes a light emitting diode matrix layer including a plurality of light emitting diodes arranged in a matrix form, and a fluorescent layer configured to alter the wavelength of the light emitted by the light emitting diode matrix layer.