Sonic Adventure (ソニックアドベンチャー, Sonikku Adobenchā) is a platform video game developed by Sonic Team. It was originally released for the Dreamcast as a launch title in 1998 in Japan, and in 1999 in western countries. It was the first game in the main Sonic the Hedgehog series since Sonic & Knuckles in 1994.After series villain Doctor Eggman releases an ancient monster, protagonist Sonic the Hedgehog vows to stop him collecting the Chaos Emeralds.