A game system includes a game apparatus and a controller. The controller
is furnished with an acceleration sensor for detecting accelerations in
at least two axis directions. Game processing corresponding to the kind
of an acceleration input by means of the controller is executed. For
determining the kind, reference timing when acceleration in a first-axis
direction is below a threshold value to take on a minimum value is
detected. Then, it is determined whether or not an angle between
acceleration change vectors before and after the reference timing is
equal to or more than a predetermined angle. When the angle is not equal
to or more than the predetermined angle, it is determined that the
acceleration input is an acceleration input in any one of the two-axis
directions, and when the angle is equal to or more than the predetermined
angle, it is determined that the acceleration input is an acceleration
input in a direction including the two-axis directions as components.