A game apparatus comprising: an input process section acquiring position information on a player wearing a head-mounted display device and moving in a play area in a real world or a housing of the game apparatus; a game process section performing a process for a game played by the player in a virtual game space in which a plurality of objects are arranged; and a display process section performing a process of displaying a game image as viewed from a given viewpoint in the game space on the head-mounted display device, the game process section causing, when the player is detected to have approached or reached a boundary of an area set as a movable range of the player in the play area or the housing of the game apparatus, a first event for performing a preventing process that prevents the player from moving in a direction toward the boundary, the game process section controlling the preventing process in the first event based on movement speed of the player, causing, when the player is detected to have moved beyond the boundary of the area, a second event for performing at least one of a process of changing an image display mode of the game image, a process of changing a game progress mode, and a process of terminating the game, and wherein, as the preventing process in the first event, the game process section performs a process of displaying an alerting object at a position corresponding to the boundary of the area, a process of displaying warning information, a process of making a given object appear in the direction toward the boundary, a process of changing a display mode of the given object in the direction toward the boundary, or a process of making a notable object or a notable event for the player appear or occur in a direction different from the direction toward the boundary. an input process section acquiring position information on a player wearing a head-mounted display device and moving in a play area in a real world or a housing of the game apparatus; a game process section performing a process for a game played by the player in a virtual game space in which a plurality of objects are arranged; and a display process section performing a process of displaying a game image as viewed from a given viewpoint in the game space on the head-mounted display device, the game process section causing, when the player is detected to have approached or reached a boundary of an area set as a movable range of the player in the play area or the housing of the game apparatus, a first event for performing a preventing process that prevents the player from moving in a direction toward the boundary, the game process section controlling the preventing process in the first event based on movement speed of the player, causing, when the player is detected to have moved beyond the boundary of the area, a second event for performing at least one of a process of changing an image display mode of the game image, a process of changing a game progress mode, and a process of terminating the game, and wherein, as the preventing process in the first event, the game process section performs a process of displaying an alerting object at a position corresponding to the boundary of the area, a process of displaying warning information, a process of making a given object appear in the direction toward the boundary, a process of changing a display mode of the given object in the direction toward the boundary, or a process of making a notable object or a notable event for the player appear or occur in a direction different from the direction toward the boundary.