A game system that allows a player to manipulate a real interface device in a real space and have a representation of the real interface device (i.e., a virtual interface device) be displayed in a virtual space is disclosed. The position of the real interface device in the real space is detected by a position detector and converted into spatial coordinates by a three-dimensional input conversion means at predetermined time intervals. When a player moves the real interface device, a virtual interface device is displayed within the virtual space and moves identically with the real interface device. The virtual interface device is determined to have struck an object in the virtual space (e.g., an enemy) when the coordinates of at least a portion of the object in the virtual space are the same as, or within a predetermined range of, the coordinates of the virtual interface device.