Sonic & Knuckles is a classic Sega Genesis game that returns to the classic platform style. Players take on the role of Sonic the Hedgehog and Sonic the Hedgehog + Sonic the Hedgehog, two of the most popular characters in the Sonic the Hedgehog series. These two games are a must-play for any Sonic fan. Sonic & Knuckles features two different game modes. In the main mode, players play through the game as Sonic and try to complete as many challenges as possible. This mode can be played in co-operative multiplayer or online. In the other game mode, Sonic & Knuckles + Sonic the Hedgehog, players take on the role of Sonic and his friends. In this mode, players must complete challenges in order to earn rewards. These rewards can include power-ups, levels, or other items.