Sonic Adventure 2 was one of the final Dreamcast releases to come directly from Sega before the system was discontinued in 2001; the game was slightly tweaked and ported to the GameCube shortly afterward, sporting new battle modes and Game Boy Advance connectivity, and furthered the precedent set by Sonic Advance of Sonic the Hedgehog appearing for the first time on a Nintendo system. The game most notably introduced two major characters: Shadow the Hedgehog, a black hedgehog with upward-curled quills, amnesia problems, and a singular focus on finding out his reason for existence, and Rouge the Bat, a large-breasted treasure hunter who harbors a healthy obsession with jewels, both of whom appear in more subsequent games than any new character introduced afterward.
Where Sonic Adventure 2's predecessor was focused on telling a multilayered story with numerous protagonists, this game took a more refined approach; instead of selecting which individual character to play as when starting the adventure, the choice was only between which faction to play, "Hero" (featuring Sonic, Tails, and Knuckles) or "Dark" (featuring Shadow, Eggman, and Rouge), and experiencing the same events from the perspective of either set of characters. In terms of gameplay, both sport similar styles (though Dark assumes that the Hero campaign has been completed first, and is noticeably more difficult in comparison); Sonic/Shadow stages focus on running through stages that have been streamlined for speed, Tails/Eggman stages feature their characters piloting mechanical walking units with ballistic/missile capabilities, and Knuckles/Rouge stages deal with their characters flying around enormous stages to find objects (usually shards of the Master Emerald) in groups of three, usually to eclectic and interesting music.
An additional feature of Sonic Adventure 2 was the inclusion of an improved Chao Garden from the original Sonic Adventure. After levels, players are able to find Chao Boxes that contain a key to enter Chao World after completing the level. After unlocking Chao World, it can also be accessed from the mission selection screen. After hatching Chao, they can participate in Chao Races and Chao Karate. In order to do well, it is important to raise the Chao's skills. To do so, players can collect Chaos Drives, animals, or feed the Chao fruit. After some time, Chao can evolve to adult forms that depend on what type of character, Hero or Dark, was used to raise it and what stat is the highest.
Hoping to find some sort of weapon, Dr. Eggman unseals his grandfather's greatest invention, Project Shadow, for the first time in 50 years. What he finds instead is a black hedgehog, claiming his name is Shadow. Now free, Shadow promises to grant Doctor Eggman one wish - but first he must meet him at the Space Colony ARK.
A week later, Sonic the Hedgehog finds himself on the run from the Military Organization, G.U.N (Guardian Unit of Nations), who claim Sonic is a dangerous criminal. Unaware of what is going on, Sonic attempts to avoid capture when he encounters Shadow the Hedgehog, who is in the middle of stealing a Chaos Emerald. Putting two and two together, Sonic assumes the Military is mistaking Shadow for Sonic (and vice versa), and this "fake" Hedgehog is the reason Sonic is in so much trouble. Before Sonic can engage Shadow in battle, however, Shadow vanishes in to thin air using a power called "Chaos Control", leaving Sonic surrounded by dozens of fully-armed G.U.N soldiers.
After Sonic Adventure 2 hit retail, SonicTeam published the Official Sonic Adventure 2 Strategy Guide in Japan, which contained "The Last Report on Project Shadow", written by the in-game character Rouge the Bat, in an effort to uncover the mystery of who - or what Shadow is, and where he came from. A summary of the report follows:
50 years ago, the current President of Nations contracted Professor Gerald Robotnik to research the possibility of immortality. Gerald initially refused, comparing it to to playing God. But when his niece, Maria Robotnik, contracted the terminal (and as-of-yet incurable) disease NIDS (Neuro-Immuno Deficiency Syndrome), Gerald reconsidered the project as a means to extend her life. The top-secret "Project Shadow" (as it became to be known due to the secrecy of the research) took place on the Space Colony known as ARK and began researching the effects of Chaos Emeralds on living tissue.
One experiment, designed to accelerate the rate of cell regeneration seen in some species of lizards, turned disastrous - the "Biolizard" subject grew ten times its normal size and became violent, nearly killing several scientists before being contained. When Military Organization G.U.N learned of the disaster aboard the ARK, they sprung in to action in order to silence Project Shadow (violently, if necessary). When they arrived aboard the ARK, Professor Gerald was already putting the finishing touches on what he called the "Ultimate Life-form", an immortal black hedgehog, named after the project he was born from: Shadow. Not knowing what the military would do with something like Shadow, Gerald entrusted Maria to take him to an escape pod and head down to the planet below.
They were intercepted by G.U.N soldiers, who, in an effort to kill Shadow, accidentally shoot Maria. With her last dying breath, she sealed Shadow in the escape pod and ejected him to earth. When Professor Gerald heard the news of his niece's death, he flew in to a rage; the very project he took part in to save her life ended up being the key to her death. Before being captured by G.U.N and sentenced to death for the "accident" on ARK, Professor Gerald gave Shadow strict instructions to carry out his revenge for what happened to Maria. Shadow was sealed in stasis to ensure that the truth about what happened on the ARK was never revealed.
2 players simultaneous
Memory blocks needed: 11
Game Boy Advance compatible
- SONIC: City Escape
- KNUCKLES: Wild Canyon
- TAILS: Prison Lane
- SONIC: Metal Harbor
- SONIC: Green Forest
- KNUCKLES: Pumpkin Hill
- TAILS: Mission Street
- KNUCKLES: Aquatic Mine
- TAILS: Route 101
- TAILS: Hidden Base
- SONIC: Pyramid Cave
- KNUCKLES: Death Chamber
- TAILS: Eternal Engine
- KNUCKLES: Meteor Herd
- SONIC: Crazy Gadget
- SONIC: Final Rush
- EGGMAN: Iron Gate
- ROUGE: Dry Lagoon
- EGGMAN: Sand Ocean
- SHADOW: Radical Highway
- ROUGE: Egg Quarters
- EGGMAN: Lost Colony
- EGGMAN: Weapons Bed
- ROUGE: Security Hall
- SHADOW: White Jungle
- ROUGE: Route 280
- SHADOW: Sky Rail
- ROUGE: Mad Space
- EGGMAN: Cosmic Wall
- SHADOW: Final Chase
Jun Senoue returns to lend his unmistakable 80's Hair Band music styles to the game's soundtrack, and he is backed up by Fumie Kumatani, Kenichi Tokoi and Tomoya Ohtani. The game contains thirteen vocal tracks, some of which are simply remixes of themes from the original game:
- "It Doesn't Matter - Theme of Sonic" by Jun Senoue and Tony Harnell
- "Believe in Myself - Theme of Tails" by Jun Senoue and Kaz Silver
- "Unknown from M.E. - Theme of Knuckles" by Kenichi Tokoi, Marlon Saunders, and Hunnid-P
- "Throw it all Away - Theme of Shadow" by Fumie Kumatani, Heigo Tani, and Everett Bradley
- "E.G.G.M.A.N. - Theme of Doctor Eggman" by Jun Senoue and Paul Shortino
- "Fly in the Freedom - Theme of Rouge" by Fumie Kumatani, Tabitha Fair, and Todd Cooper
- "Live and Learn - Main theme of Sonic Adventure 2" by Jun Senoue and Johnny Gioeli from the band Crush 40
- "Escape from the City - ...for City Escape" by Jun Senoue, Tony Harnell, and Ted Poley
- "Kick the Rock! - ...for Wild Canyon" by Tomoya Ohtani
- "A Ghost's Pumpkin Soup - ...for Pumpkin Hill" by Tomoya Ohtani
- "That's the way I Like It!" For Metal Harbour by Jun Senoue
- "Rhythm and Balance" For White Jungle
- "Dive Into The Mellow - ...For Aquatic Mine" by Tomoya Ohtani
- "Deeper - ...for Death Chamber" by Tomoya Ohtani
- "Space Trip Steps - ...for Meteor Herd" by Tomoya Ohtani
- 'On the Edge" for Eternal Engine