Sonic Adventure

Sonic Adventure was the first true 3D Sonic title. It was tentatively titled "Sonic RPG" due to the exploration and puzzle-solving elements. It was a title released for the SEGA Dreamcast in 1999, to much fanfare.

It included six playables characters, many with their own levels. (Some of the characters shared levels with other characters.)

The playable characters were: Sonic the Hedgehog, Miles "Tails" Prower, Amy Rose, Knuckles the Echidna, and two newcomers to the Sonic world: Big the Cat, a large purple cat whose passion is fishing and has a frog "Froggy" for a best friend, E-102 "γ", who is a robot created by Dr. Eggman plus Super Sonic.

Sonic Adventure introduced the "Chao" or "A-Life" which were basically virtual pets that were neccesary for earning several emblems. Some people hate them, while others enjoy raising them. Either way, they're essential for a 100% complete game.

For this game, Sonic Team actually went to Central and South America to study the landscape and environment. One of the villages they visited even influenced the name of a character in the game, Tikal.

The story of the the game focuses on Dr. Eggman finding several ancient tablets, and discovering how to revive "Chaos", the ancient God of Destruction. As the story progresses, Chaos gets stronger and stronger, as Eggman feeds him more Chaos Emeralds. Eventually, Chaos has absorbed all seven Chaos Emeralds (becoming Perfect Chaos and floods Station Square and generally wreaks havoc. Luckily, Sonic arrives just in time, and transforms into Super Sonic, and proceeds to beat Chaos back down to his regular form.

Sonic Adventure DX: Director's Cut

Sonic Adventure DX: Director's Cut, or simply "SADX" was a re-release of the original Sonic Adventure onto the Nintendo GameCube. It featured souped-up graphics, unlockable Game Gear games, an updated Chao Garden, a new "Mission Mode" featuring 60 objectives, and a Metal Sonic skin for Sonic (as a reward for 130 emblems).