Abstract: Two panels each having an opaque background with an array of transparent dots therein are superimposed in front of a light source. The array of transparent dots in one panel is arranged to form a rectangular grid while the transparent dots in the other panel are positioned along the diagonal lines of the rectangular grid. Three transparent dots are positioned along the diagonal line between diagonally opposite pairs of transparent dots on the rectangular grid. The transparent dots along the diagonal lines are arranged to form three separate patterns, each of which may be a letter, a word or group of words, a picture, or a design. One of the panels is periodically reciprocated along the diagonal lines relative to the other panel, which causes the three separate patterns to be illuminated in sequence, each illuminated pattern being extinguished before the next pattern is illuminated.