INPUT DEVICE, INPUT DETERMINATION METHOD, GAME SYSTEM, GAME SYSTEM CONTROL METHOD, PROGRAM, AND INFORMATION STORAGE MEDIUM

With a game system, a timing fetch section fetches an input-timing for input data determined to be valid by an input-determination section, and an evaluation section compares the fetched input-timing and a reference-timing, and evaluates an operation with an operation section by a player or a sound-input action performed in answer to a first or second direction-mark. An input-reception section receives first and second input data generated based on an operation-detection of the operation section a sound-detection of the sound-detection section, respectively, and an input-determination section compares the first and second input data, determines that the first input data is valid when it is determined that the operation with the operation section by the player and the sound-input action by the player overlap within a given period, based on the first and second input data, and determines that the first and second input data are valid in other cases.