Two Sides of the Same Fight
Sonic Adventure 2 splits its story into a Hero side and a Dark side. You play as Sonic, Tails, and Knuckles on one path, and as Shadow, Dr. Eggman, and Rouge on the other. Each character brings their own skills to the stages, so the same level can feel quite different depending on who you are controlling. The two paths run in parallel as both groups hunt the Chaos Emeralds, and the story only comes together once you have played through both.
Playing Together
The main story is a single-player experience, but the game has a separate competitive side built for two players. You can take a break from the campaign and race karts against a friend, or pick from the other competitive modes on offer. Split screen is supported locally, and Remote Play Together lets a friend join over the internet as if they were sitting next to you. The versus modes are separate from the main story, so nobody has to share progress or wait for the other person to catch up.
Chao Raising and Missions
Outside of the stages, you can raise a pet Chao, improve its stats, and enter it into Chao mini-games. This runs alongside the main campaign rather than inside it, so it works as a side activity whenever you want a change of pace. The game also carries over 150 missions spread across 30 stages, which gives each level reasons to be replayed beyond simply reaching the end. Between the two story paths, the mission list, and the versus modes, there is a lot of ground to cover before you have seen everything.