In a game system, a player can displace direction of a view line disposed in a three-dimensional space coordinate system to change the corresponding perspective-projected image by changing the aim of the gun-type controller, by setting a specific region on a perspective projection plane; detecting a designated position with respect to a display plane, which is designated; determining whether or not the designated position is located in a specific region; displacing the view line direction or moving the view point position based on the positional relationship of the designated position and the specific region when the designated position is not positioned inside the specific region; and finding a two-dimensional image obtained by perspective projection in the new view line direction after the displacement of the view line direction or movement of the view point position and displaying two-dimensional images on the display device.