Nano's staff is not only used as a melee weapon. It's also used to fire goo bombs. When launching the bombs, Nano has to attach his staff to a tank strapped to his back containing the goo. When the tank is empty, it automatically refills itself. The bombs only use up a small amount of goo which expands itself inside the grip of the staff. The shells are instantly created when Nano presses a button to create a bomb and presses it again to fire.
