Sonic Adventure 2

Good vs. Evil
The main game theme is the fight between good and evil, so the entire story is divided between two sides, both playable: Hero and Dark. Each side has a Racing, a Treasure Hunting and a Shooting character. Each character has a rival counterpart in the other team.

Hero Side Story
Sonic the Hedgehog has been wrongfully imprisoned for crimes he did not commit; after escaping the clutches of the military, he discovers an impostor hedgehog known as Shadow, who has been going around stealing Chaos Emeralds. Shadow claims to be "The Ultimate Life-Form", and has teamed up with Dr.Eggman and the thief Rouge the Bat to gather the seven Chaos Emeralds, with the intention of powering the Eclipse Cannon. Unfortunately for them, Sonic, Tails, and  Knuckles, (along with help from  Amy) are there to make sure the emeralds don't fall into the wrong hands. But will the team really be able to stop the Eclipse Cannon from firing?

Dark Side Story
Hot off the disaster in Station Square, Dr. Eggman wastes no time in continuing his plot for world domination. Catching wind of a military weapon his Grandfather, Professor Gerald Robotnik had been working on for the goverment, Eggman forcibily breaks into Prison Island to unseal "Project Shadow" - a biomechanical hedgehog who has amazing speed and - most impressively, the power of "Chaos Control"; an ability which allows him to warp space and time to suit his needs. Shadow promises Eggman he will grant him one wish, as long as Eggman brings the seven Chaos Emeralds to the Space Colony ARK. There resides the ultimate weapon the Eclipse Cannon; a massive energy cannon with the power to destroy an entire planet. It has been abandoned for 50 years so it needs the anciet powers of the seven Chaos Emeralds to recharge. But what are Shadow's true motives? Does he really want to conquer the Earth, or to destroy it?

Single Player
As you play, the game will change characters according to the plot and which side you choose; HERO or DARK. For example: If you choose HERO, on one stage you may play as Sonic, and on the next stage, you play as Knuckles. Depending on how well you do in the stages, determines your grade when you finish the stage. The higher your score is, the higher your grade will be. (The Grades being A, B, C, D, and E, with E being the worst)

Racing
The speedy gameplay you know and love, players must run to the end of the stage, gathering the most items and rings as possible in the least amount of time.
 * HERO: Sonic the Hedgehog
 * DARK: Shadow the Hedgehog

A rank: Try to focus on the time you complete the level.

Shooting
Shooting is just that: Shooting. The player boards a mech, and plays using a modified version of E-102 Gamma's gameplay from Sonic Adventure. Using laser sights, the player locks on to multiple targets at a time and fires away. The more targets you lock on to at one time, the higher your bonus is.
 * HERO: Miles "Tails" Prower
 * DARK: Dr. Eggman

A rank: Kill as many enemies and get as many combos.

Treasure Hunting
Slower and based much more heavily on exploration, Treasure Hunting segments force the player to find three items in the least amount of time possible. To help you find the items, you are given a radar that beeps depending on how close you are to the item.
 * HERO: Knuckles the Echidna
 * DARK: Rouge the Bat

A rank: find a common path to follow when sniffing out emeralds and then branch out from there.

Driving
The game features two levels in story mode with kart racing, where Tails or Rouge must drive to the other side without falling off the course or hitting too many cars. There's also a mode with all the characters playable, where you must finish a few laps before the other CPU players, and you get an emblem if you do. You unlock the mode by beating one of the racing levels. Beating the other gives you a Two Player version.
 * All characters

A rank: Focus on time.

Hero Side

 * City Escape - Sonic (Racing)
 * Boss: Bigfoot - Sonic (Racing)
 * Wild Canyon - Knuckles (Hunting)
 * Boss: Dr. Eggman - Tails (Shooting)
 * Prison Island - Tails (Shooting)
 * Metal Harbor - Sonic (Racing)
 * Boss: Shadow - Sonic (Racing)
 * Green Forest - Sonic (Racing)
 * Pumpkin Hill - Knuckles (Hunting)
 * Mission Street - Tails (Shooting)
 * Aquatic Mine - Knuckles (Hunting)
 * Route 101 - Tails (Driving)
 * Hidden Base - Tails (Shooting)
 * Pyramid Cave - Sonic (Racing)
 * Death Chamber - Knuckles (Hunting)
 * Boss: King Boom Boo - Knuckles (Hunting)
 * Boss: Egg Golem - Sonic (Racing)
 * Eternal Engine - Tails (Shooting)
 * Meteor Herd - Knuckles (Hunting)
 * Boss: Rouge - Knuckles (Hunting)
 * Crazy Gadget - Sonic (Racing)
 * Boss: Dr. Eggman - Tails (Shooting)
 * Final Rush - Sonic (Racing)
 * Boss: Shadow - Sonic (Racing)

Dark Side

 * Iron Gate - Eggman (Shooting)
 * Boss: Hotshot - Shadow (Racing)
 * Dry Lagoon - Rouge (Hunting)
 * Sand Ocean - Eggman (Shooting)
 * Radical Highway - Shadow (Racing)
 * Egg Quarters - Rouge (Hunting)
 * Lost Colony - Eggman (Shooting)
 * Weapons Bed - Eggman (Shooting)
 * Boss: Tails - Eggman (Shooting)
 * Security Hall - Rouge (Hunting)
 * Boss: Flying Dog - Rouge (Hunting)
 * White Jungle - Shadow (Racing)
 * Boss: Sonic - Shadow (Racing)
 * Route 280 - Rouge (Driving)
 * Sky Rail - Shadow (Racing)
 * Boss: Egg Golem - Eggman (Shooting)
 * Mad Space - Rouge (Hunting)
 * Boss: Knuckles - Rouge (Hunting)
 * Cosmic Wall - Eggman (Shooting)
 * Boss: Tails - Eggman (Shooting)
 * Final Chase - Shadow (Racing)
 * Boss: Sonic - Shadow (Racing)

Last Story

 * Cannon's Core - Everyone but Shadow (All styles)
 * Boss: Biolizard - Shadow (Racing)
 * Final Boss: The Final Hazard - Super Sonic/Super Shadow (Superpowered Racing)

Secret

 * Green Hill Zone - Sonic (Racing)

Racing

 * Amy Rose (originally Sonic's alternate, updated from SA2 to have lower speed and no spin dash but Special Attacks at lower costs.)
 * Metal Sonic (originally Shadow's alternate, updated from SA2 to have sound, a shield over a spin dash and faster speed, but no Special Attacks.)

Treasure Hunting

 * Chaos 0 (originally Rouge's alternate, updated from SA2 to have slower speed but more powerful attacks and the ability to breathe underwater.)
 * Tikal (originally Knuckles' alternate, updated from SA2 to have higher speed but weaker attacks and a poorer radar.)

Shooting

 * Chao Walker (originally Tails' alternate, updated from SA2 to have weaker attacks but higher speed)
 * Big the Cat (Dreamcast version only), Dr. Eggman's original alternate
 * Dark Chao Walker (GameCube Version only), Dr. Eggman's new alternate, has lower speed but stronger attacks than Chao Walker

Easter Eggs and Trivia

 * The original plan for Sonic Adventure 2 was very different from how the finalized game ended up; Originally it is thought the game would feature only Sonic, Knuckles, and Eggman as playable characters, but, after fan outcry of key characters (specifically Tails) not being playable, Tails, Rouge, and Shadow were added to the roster of playable characters.
 * Additionally, the game was to feature branching storyline pathways: At key points of the game, the character you were playing as would be presented with a choice on how to solve a situation. Depending on your answer, it would change what levels your character visited. This concept was removed midway through development, but eventually ended up being implemented in 2005's Shadow the Hedgehog.
 * This was the first game the San Francisco based Sonicteam USA had developed, and many stages in the game were inspired by the developer's new California based location; the steep hills of City Escape are ment to represent San Francisco, while the huge bridge in Radical Highway and Mission Street are ment to represent the Golden Gate Bridge and surrounding area. Route 101 and Route 280 were named after actual highways in the San Francisco Bay Area.
 * Sonicteam went to great lengths to ensure the name and appearance of the character Shadow the Hedgehog remain as secret as possible. Eventually these details were leaked accidentally by toy company ReSaurus when they announced they would be producing Sonic Adventure 2 action figures. (These figures were never actually produced, as ReSaurus went out of business)
 * Packaged in with Online RPG Phantasy Star Online, the original demo for Sonic Adventure 2 contained many slight changes over the final version of the game; most notable was the fact that Sonic was still wearing his original trademark shoes. It wasn't until a few months before the retail release of Sonic Adventure 2 that Sonicteam revealed a merchandising deal with Soap Shoes.
 * Other changes in the demo include different road-side billboards, different sound effects, looser controls, and a different instrumental version of the song, Escape from the City.
 * Originals prototypes for Shadow: name was Terios, aura was black.
 * In addition to the standard release of the game, an exclusive 10th Anniversary Birthday Pack was released. It included many extras, such as a limited edition coin (stamped with Sonic's face), a leather bound case, a 10th Anniversary History Booklet, and a special soundtrack CD, containing music from many of Sonic's more notable videogame appearances over the last 10 years.

Voice Cast
Ryan Drummond - Sonic

Corey Bringas - Tails

Scott Drier - Knuckles and President

Jennifer Douillard - Amy

Deem Bristow - Eggman and Gerald Robotnik

Lani Minella - Rouge and Secretary

Rouge's Report
As Sega often does, in the japanese Official Strategy Guide to Sonic Adventure 2, some interesting and exclusive content was provided that sheds slightly more light on the events that transpire in the plot; "A partial excerpt from the last investigative report by Rouge, about Project Shadow". Rouge, who was a double agent for the goverment in Sonic Adventure 2, gives us a peek at what she uncovered about Shadow the Hedgehog's mysterious origins.

In it, Rouge notes she has discovered a letter to Professor Gerald Robotnik from the President of that era, requesting that Gerald research "mankind's ultimate dream", the secret to eternal life. Gerald would have no part in the research, declaring that it was "like playing God". Further research on Rouge's part reveals that Gerald was ultimately forced to accept the position after his Grand Daughter, Maria Robotnik, contracted the disease NIDS (Neuro Imuno-Deficiency Syndrome, Sonic Adventure 2's fictional representation of AIDS). With no cure for NIDS, Gerald entered the program in hopes that he could treat her illness using data he gathered from his research into eternal life.

Thus, Project Shadow was born, aboard the Space Colony ARK. Here, the confidential research began by experimenting on Lizards, and their regenerative growth abilities. However, applying Chaos Emerald Energy to the test subject became too risky, and it became violent and out of control. It is unknown how, but information about an accident involving a mutated lizard, "The Proto-Type of the Ultimate Life-Form", was leaked to G.U.N. By taking advantage of the situation aboard ARK, G.U.N. enacted a procedure under the codename, "ARK's Indestructable Seal", with the ultimate goal of erasing the existance of Project Shadow indefinitely.

However, there was a miscalculation: By the time G.U.N. arrived on ARK, they discovered Gerald was already placing the finishing touches on the finalized "Ultimate Life-Form", a hedgehog named Shadow. Gerald, Maria, and Shadow attempted to escape the ARK before the G.U.N. could seize Shadow - but in the commotion, Maria was shot. With her last ounce of strength, she ejected Shadow's escape pod to Earth. It is currently unknown if the Shadow that Eggman uncovered on Prison Island is the Shadow ejected from the ARK that fateful day.

Sonic Adventure 2: Battle
There is an update to Sonic Adventure 2 for the Nintendo GameCube, called Sonic Adventure 2: Battle. This version was released on December 10, 2001 in Japan, July 3, 2001 in North America, and April of the same year in Europe.

This game added new "Battle" multiplayer options, like the addition of new charactistics to the additional multiplayer characters that were in the available unlockable in the original. The multiplayer characters that were unlockable in the other game are now playable from the start, and other new bells and whistles were added. Unfortunately, some alternate costumes were removed when porting the game, as well as extracting Big from cameos (except for on the Dark story) and replacing him with a Dark Chao Walker.

This game also changed a large portion of raising Chao, the life form available in both Sonic Adventure and Sonic Adventure 2. A Chao's stats can be viewed from within the game. You can also transfer one Chao from Sonic Adventure 2: Battle to Sonic Advance, Sonic Advance 2, and Sonic Pinball Party with the GCN-GBA Link Cable. Also the introduction of Chao Karate, in which the Chao stats are used for stats in fighting, and the Chao fight in a fighting game style, with little influence from the player.

In both the Dreamcast and Gamecube version, after collecting all 180 emblems, you can unlock a 3D version of the Green Hill Zone from Sonic 1, with a remixed version of the music from the original.

Ironically, this version of the game did not get as good reviews as its Dreamcast predecessor, possibly as it was seen as technologically behind most other GameCube games (the graphics were largely left untouched).