The stepper motor driven discs are approximately 3" in diameter and their surfaces are painted either white or black with corresponding smaller dots of "opposite" color (note: there is no lighting inside this clock). Each disc has 4 positions when telling the time such that a dot points to 12 (0 value), 3 (1 value), 6 (2 value) or 9 (3 value). The hour is told by adding up the values on the 4 white discs. The 10s of minutes told with the black discs in the upper left and lower right corner. The minutes are told using the 3 black discs along the diagonal running from upper right to lower left corners. It may be possible/desirable for the discs to put on a show until prompted to reveal the time.