Sega's speedy mascot returns to his 2D side-scrolling roots in the high-definition, download-only title Sonic the Hedgehog 4: Episode I. Set shortly after the conclusion of Sonic & Knuckles, the game finds Sonic enjoying some solo adventures when his old nemesis, Dr. Ivo Robotnik, once again spoils the fun with a variety of aggressive robot enemies. Using familiar moves like the spin dash and the homing attack, players must guide the famed blue hedgehog through four different three-level zones, each culminating in a classic Sonic boss battle.
Special stages reminiscent of the original Sonic the Hedgehog find gamers navigating mazes to collect chaos emeralds, and once all seven jewels have been recovered, players can transform into Super Sonic. ~ Christopher Brown, All Game Guide