Sonic Adventure 2 is a 2001 platform game developed by Sonic Team USA and published by Sega for the Dreamcast. It features two good-vs.-evil stories: Sonic the Hedgehog, Miles "Tails" Prower, and Knuckles the Echidna attempt to save the world, while Shadow the Hedgehog, Doctor Eggman and Rouge the Bat attempt to conquer it. The stories are divided into three gameplay styles: fast-paced platforming for Sonic and Shadow, multidirectional shooting for Tails and Eggman, and action-adventure exploration for Knuckles and Rouge. Development began soon after the American release of Sonic Adventure in 1999 and lasted 18 months. Sonic Adventure 2 was produced in commemoration of the Sonic series' tenth anniversary and was designed to be faster-paced and more action-oriented than the original. The development team expanded upon the presence of the Chao creatures and other player characters. Its locations were influenced by American locations such as San Francisco and Yosemite National Park. Sega announced Sonic Adventure 2 in October 1999 and exhibited it at E3 2000. Sonic Adventure 2 was released in June 2001. It was the final Sonic the Hedgehog game for a Sega console, released in the months after Sega discontinued the Dreamcast and transitioned to third-party development. It received positive reviews, with praise for its gameplay variety, visuals, and audio but criticism for its camera, voice acting, and plot. A port for the GameCube was released in late 2001 in Japan and early 2002 in North America and Europe. It features improved textures and multiplayer options. Together, the Dreamcast and GameCube versions sold more than two million copies worldwide. A downloadable version was released for the PlayStation 3, Xbox 360, and Windows in 2012.