The listing, Sonic Adventure DX (Steam Key) has ended.
https://store.steampowered.com/app/71250/Sonic_Adventure_DX/
About This Game
An ancient evil lurking within the Master Emerald has been unleashed from its slumber by the devious Dr. Eggman and is on the verge of becoming the ultimate monster using the 7 Chaos Emeralds. Only Sonic and his friends are heroic enough to put a stop to Dr. Eggman and his evil minions. Hit the ground running in this classic epic adventure in a race against time to save the world!
Features
Six Characters, Six Adventures
Play through as one of six different characters, including Sonic, Tails, Knuckles, and Amy, each with their own unique adventure and story.
Breed a Pet Chao
Breed and nurture your very own pet Chao in the Chao Garden minigame. Then compete against other Chao in a battle for ultimate Chao supremacy.