Storage medium having game program stored thereon and game apparatus

First acceleration data representing an acceleration applied in a first direction of the input device and second acceleration data representing an acceleration applied in a second direction of the input device different from the first direction are obtained based on a value detected by an acceleration detection section. Next, it is determined whether or not the first acceleration data is smaller than a first threshold value. When the first acceleration data is determined to be smaller than the first threshold value, predetermined calculation processing at least based on the second acceleration data is executed to calculate a first parameter used in game processing. When the first acceleration data is determined to be larger than the first threshold value, the first parameter is set to a predetermined value. The game processing is executed based on the first parameter.