Provided is a game system in which, when the game device is tilted, the tilt is reflected in the game, making the game more fun. This game system provides a game in which, when an object (O) reaches a player's first decision line (La), the object (O) can be hit back to a second decision line (Lb) by the player's operation of a touch panel (3). In this game system, the game device (1) is provided with a detection unit (4) which detects the tilt of the game device (1) relative to the horizontal plane (H), and when the player operates the touch panel (3), if the detection unit (4) detects a tilt of the game device (1), then in some section (W1a) of the path of motion of the object (O), the object (O) moves at a movement speed set depending on the tilt, and in the remaining sections (W1b), the object (O) moves at a movement speed set such that the object (O) will move from the first decision line (La) to the second decision line (Lb) in a prescribed set time.