Sonic & Knuckles

Sonic & Knuckles is a game developed by Sonic Team and published by for the Sega Genesis in 1994. It is the fourth installment in the main Sonic the Hedgehog series and a direct sequel to Sonic the Hedgehog 3. Sonic 3 & Knuckles were originally intended to be a single game. However, due to time constraints and the cost of a large-memory-capacity cartridge, Sega split the game in two.

Original description:

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!
Lock-on with Sonic 3 and transform Floating Island into a huge 34 meg Sonic-epic loaded with new secrets! Play as Sonic, Knuckles, and even Tails - with Game Save!
Lock-on with Sonic 2 and play as Knuckles with all his signature moves!

Instructions

Enter - start;    Arrows - move;    Z X C - jump;    Esc = exit fullscreen;

You can change keyboard settings, save (F5) and load (F8) the game.
Put your mouse over the game and choose your settings, you can also play the game in fullscreen.