a user interface display system can include at least one user responsive element . the user responsive element can include an optical mechanism . a pulsed light source can produce a light beam . apparatus are provided for causing the light beam to repeatedly scan across the activity field . a controller can be arranged to repeatedly turn the light source on at one or more predetermined scan positions to illuminate the user responsive element . the controller can also be programed to act upon a signal regarding the status of the element . a photo detector can send the signal to the controller . the optical mechanism acts upon the light beam differently based upon the status of the user responsive element .