The icon 348 of a graphic user interface indicates the magnitude of an inputted impact by an impact pointer 348d which moves as the time elapses and receives input of the impact. Magnitude of the impact received by a GUI 34 is retained in the impact data as a product of the moving amount of the impact pointer 348d and a scale factor, of which the value can be switched together with the indication form of a gauge 348c depending on the movement of a slider 348a. Consequently, more realistic regulation of impact, e.g., half shot, can be attained when a ball is hit in a sport simulation game such as a golf game.