ステップ関数
:blank::blank::blank::blank::blank::top_left_sushi::blank::top_center_sushi::blank::top_center_sushi:
:blank::blank::blank::blank::blank::middle_left_sushi:
:blank::blank::blank::blank::blank::middle_left_sushi:
:top_center_sushi::blank::top_center_sushi::blank::top_center_sushi: