A game system includes a housing to be held by a player. The housing incorporates an XY-axis acceleration sensor to detect an acceleration in a X-axis direction and a Y-axis direction and a Z-axis contact switch to detect an acceleration in a Z-axis direction. The sensor and switch detect at least one of an amount (e.g. tilt amount, movement amount, impact amount or the like) and a direction (e.g. tilt direction, movement direction, impact direction or the like) of a change applied to the housing. A simulation program provides simulation such that a state of a game space is changed related to at least one of the amount and direction of the change applied to the housing.