Abstract: A data obtaining unit repeatedly obtains acceleration data. An acceleration vector generation unit generates first acceleration vector in accordance with first acceleration data obtained by the data obtaining unit, and generates second acceleration vector in accordance with second acceleration data time-sequentially obtained by the data obtaining unit following the first acceleration data. A cross product direction calculation unit calculates a direction of a cross product between the first acceleration vector and the second acceleration vector. A swing direction identification unit identifies a swing direction in which the input device is swung in accordance with the direction of the cross product.

Abstract: Data obtaining means repeatedly obtains acceleration data. Acceleration vector generation means generates first acceleration vector in accordance with first acceleration data obtained by the data obtaining means, and generates second acceleration vector in accordance with second acceleration data time-sequentially obtained by the data obtaining means following the first acceleration data. The cross product direction calculation means calculates a direction of a cross product between the first acceleration vector and the second acceleration vector. The swing direction identification means identifies a swing direction in which the input device is swung in accordance with the direction of the cross product.