Abstract: The sound of the swing of a golf club is sensed and actuates a circuit to randomly select one of a plurality of visually distinctive indicia, such as different colored LEDs or flags, for a fraction of a second. One set of indicia is located on the ground proximate the ball. In order to observe and identify the selected indicia, the golfer must keep his head down and steady during the swing. A second set of identical indicia may be provided for use by an instructor. The second set of indicia may be located remotely from the first.