Sonic and Knuckles join forces to defeat rotten Dr. Robotnik's Death Egg invasion! Play Sonic & Knuckles by itself or Lock-on with other Sonic games. This game's revolutionary Lock-on technology adds all new features to your other Sonic games for ultimate replays! Play as Sonic and let loose on Robotnik with amazing new powers. Play as Knuckles and tackle Robotnik and Metal Sonic with bare-fisted attacks, high-speed glides and wall-climbing power!