Sonic Adventure is a platform game in which the player controls six different characters: Sonic the Hedgehog, Miles "Tails" Prower, Knuckles the Echidna, Amy Rose, Big the Cat and E-102 Gamma. They must stop Doctor Eggman from stealing the seven Chaos Emeralds and feeding them to Chaos, a monster known as "the God of Destruction". The first in the Sonic the Hedgehog series to feature free-roaming 3D gameplay, Sonic Adventure features two game modes: Adventure and Trial. There are different goals for each character in the game: Sonic involves high speed gameplay, while Tails must reach the end of the level before Sonic does and Knuckles searches the area for shards of the Master Emerald. Each of the three characters retain many of their trademark moves from previous Sonic games, though they can use updated techniques. Amy must escape from the E-100 Zero robot chasing after her, Gamma shoots through levels to reach a target and Big fishes for his friend, Froggy.