[0239] As described above, in the second configuration example, a portion of the top surface portion 303 that forms the cut-out portion C1 (in other words, a portion around the cut-out portion C1) functions as a stop-receiving portion with which the stop member is to engage. In the second configuration example, the slide movement of the left controller 3 attached to the main unit 2 is limited (or "locked") by the stop-receiving portion and the stop member 319, instead of the engagement hole 16 and the projection 41 in the first configuration example, the details of which will be described later. Note that a state in which the slide movement is limited (in other words, "locked") is a state in which the stop member 319 is interfered by the stop-receiving portion, thereby preventing the slide movement. Note that "to limit (or lock)" the slide movement means to prevent the slide movement with a force less than a certain level, and means that the slide movement may be allowed when a force greater than a certain level is applied (thereby disengaging the stop member 319 from the stop-receiving portion).