Abstract: After a batter hits a ball, the height of the ball moving on a trajectory passing through present movement positions is judged. For example, future movement positions positioned on a time axis ahead of the present movement positions are indicated on the ground by elliptical marks. The peak of the height becomes a boundary, and in a rising process of the ball, the mark is displayed in a first color, and in a falling process of the ball, the mark is displayed in a second color. Therefore, the enjoyment of operations by the combination of the operation support of a computer and the operation skill of the user himself can be obtained.