"Sonic Adventure 2" is a 3D platform game divided into two campaigns: Hero and Dark. In the Hero campaign, players control Sonic, Tails, and Knuckles, who fight to save the world; in the Dark campaign, players control Shadow the Hedgehog, Doctor Eggman and Rouge the Bat, fighting to conquer it. Each campaign cycles through levels of its three characters, telling different sides of the story. Levels have a variety of themes (such as cities, jungles, desert pyramids and outer space), with some followed by boss fights. The two campaigns' stories occur in parallel; completing both campaigns unlocks a Last Story with all six characters, culminating in a final boss fight.