Sonic Adventure 2 is a 2001 platform video game developed by Sonic Team USA and published by Sega. The sequel to Sonic Adventure, it was the final Sonic the Hedgehog game for the Dreamcast after Sega discontinued the console. 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, multi-directional shooting for Tails and Eggman, and action-exploration for Knuckles and Rouge.Go to: http://store.steampowered.com/ and download STEAM client
Click “Install Steam” (from the upper right corner)
Install and start application, login with your Account name and Password (create one if you don’t have).
Please follow these instructions to activate a new retail purchase on Steam:
Launch Steam and log into your Steam account.
Click the Games Menu.
Choose Activate a Product on Steam…
Follow the onscreen instructions to complete the process.
After successful code verification go to the “MY GAMES” tab and start downloading.