A turning point marker on a power gauge and an impact point object are displayed in a game image. The impact point object is displayed according to the current lie. The turning point marker is positioned away from the left end of the power gauge depending on the difficulty of the shot. The moving direction of a cursor moving along the power gauge is reversed at the turning point marker. With the turning point marker, it is possible to clearly indicate to the player how limited the power available is under the current situation as compared with the situation where the maximum power is available, and thus how difficult it is to play the current situation.