Review
Sonic & Knuckles revisits the trials of Sega's little blue hero as he once again takes on the wily Dr. Robotnik. The fiend has stolen the Master Emerald and kidnapped all of Sonic's pals to use in his robot army. Sonic is off to save the day ... or it could be Knuckles, depending on whose adventure you choose. There are two slightly separate adventures contained on the cartridge, and you can choose either the super-speedy Sonic, complete with his new shield abilities (there are a number of shields in the game, each possessing different powers), or Knuckles' brute strength and ability to fly.
While the gameplay will be immediately familiar for anyone who has ever played a Sonic game before, with its customary loops, dips, flats and platforms, the addition of a new playable character is a highly welcome feature, especially given that the game itself still feels very much like Sonic 3 with a bit of a facelift. The overall redundancy is certainly the game's biggest shortcoming, and those already tired of the series will not find anything in this update to recapture their interest.
The challenge of the game is decent, however, and there are some new surprises found within, including an all-new bonus stage system for collecting the chaos emeralds that can open up secret areas for you as you play. Knuckles' play is significantly different than Sonic's, especially with his flight ability. And the robotic enemies, bosses and levels are competently designed, even if they lack the inspiration of previous outings, mainly because there isn't much more to do with them in this, the fourth Sonic game on the Genesis.
What makes this title unique, however, is its ability to "lock-on" to Sonic 2 and Sonic 3. For any other Genesis game, you can press A, B, and C to get a special randomized special stage that varies in difficulty, but the other Sonic games actually give you more. In Sonic 2, you can play through the game as Knuckles. Sonic 3 and Sonic & Knuckles together gives you the ability to play through them both back to back, as either Sonic, Tails or Knuckles, and allows all three to "hyper" up with the capture of all the Chaos emeralds. While the obvious caveat to this is the fact that you actually need other games to do it, this lock-on feature is certainly welcome for those with a Sonic library.
The graphics in Sonic & Knuckles are detailed and robust, but on the whole they don't look terribly different from the other Sonic games. The series has always looked great for the Genesis, but the visual similarities between them hurts the later entires, causing them to lack singular appeal and become muddled together. Sonic & Knuckles still features decent music, although once again the Genesis's inferior sound processor is showing its age, sounding as if it's playing the songs from deep inside the heart of a tin can.
Sonic & Knuckles proves there's still some life beating through the heart of our favorite hedgehog, and the enjoyable nature of this title, as well as the creative addition of the lock-on feature, makes it a fitting farewell on the Genesis.
Graphics 
While the graphics are derivitive of the other games in this series, they are still bright, crisp, and pleasing to behold.
Sound 
The music is well composed, but the problem with it is mainly the fault of the Genesis' weak sound processor.
Enjoyment
It is just another Sonic game, but like the rest, this title offers a great amount of entertainment. Take the two different characters, and you have twice the game. It isn't a unique experience, but it certainly will keep you occupied for a good while.
Replay Value
Two different characters is great, but what's even better is the lock-on technology, which opens up whole new worlds with the other Sonic games.
Documentation
The manual does a good job of explaining how to play the game, as well as illustrating the basics of the lock-on feature.
