A non-limiting example game system includes a processor incorporated in a main body apparatus, and the processor makes a first index image move toward an upper end from a lower end in a movement gauge in a parameter determination screen when a player starts a second parameter determination operation. When the first index image is stopped according to an operation of the player, a hitting power for a ball is determined based on the stopped position. Moreover, if the first index image is stopped, a second index image is moved up to a position that the first index image is stopped from the lower end in the movement gauge. The player performs a direction input during a direction input period that is a period of time that the second index image is being moved. Then, a trajectory after the ball starts moving is changed in a direction based on the direction input. For example, when a parabola that becomes a reference when hitting the ball is used as a reference trajectory, and this reference trajectory is changed based on the direction input.