Sonic & Knuckles(1994). The fourth Sonic game on the Genesis (or 2nd half of the third, if you prefer to call it that).
Once upon a time, Sega became a worthy 16-bit contender in the early 90s thanks to the release of a fast-paced adventure starring everyone's favorite blue hedgehog, Sonic. Then the series really took off in 1992 with the release and success of its sequel. The Sega CD harbored Sonic CD, a worthy cult classic, though for some reason it became forgotten over time. This brings us to "Hedgehog Day" of 1994, when Sonic 3 was unleashed on the public. Originally, the game was slated to be one massive adventure, but in order to meet deadlines, Sega decided to cut it in half, give the fans the first part of the game early on, and save the rest of it for a later date in the year. In the meantime, Sega also thought about incorporating a special "lock-on" feature to this second half of the 3rd Sonic game which allowed one to stick Sonic 2 and 3 on top of it, and it would change the game to a certain degree. Of course, lock on technology was nothing new (*cough* Game Genie *cough*), but this was the first time that it was incorporated for a specific purpose, more of which I'll get into soon.
So this time, Sonic must traverse the rest of Angel Island after bringing down the Death Egg (again) onto a volcano and stop Dr. Robotnik once and for all. However, Tails is gone for this round in place of being able to play as Knuckles the Echidna for the first time. He taunted and tricked you all throughout Sonic 3, but now you can rip through the stages as him, or get your revenge on him at last with Sonic. Either way, S&K holds up as its own giant adventure, with the same size of levels, graphics engine, powerups, and other features as the previous game. I've covered the basics of the game in my Sonic 3 review, so I'll just go into the new stuff here:
-LOCKING ONTO THE OLDER GAMES GIVES THEM A NEW FRESH REPLAYABILITY. Stick it onto Sonic 2, and now you're traversing the Casino Nights, Hill Tops, and Wing Fortresses of old as Knuckles given the advantage of his new abilities. However, stick it onto Sonic 3 and you'll get the massive adventure that Sega wanted to release all along - in other words THE BIGGEST AND BEST SONIC GAME EVER CONCEIVED. Play as all three of the furballs going through both games and collecting 14(!) chaos emeralds to become... HYPER SONIC! On top of that, stick it onto Sonic 1 or any other Genesis game and you'll now have access to unlimited random Special Stages styled from Sonic 3.
-KNUCKLES IS A NICE ALTERNATIVE TO PLAY AS FROM THE OTHERS. He doesn't fly like Tails or jump as high as Sonic, but his glide, climbing, and smashy fists enable him to reach places that the others can't get to. Plus, a lot of the areas of certain zones that you traverse are completely different from Sonic's.
-COOL NEW BONUS STAGES. There are two of them now, and are far easier to access as well. One is an energy sphere magnetic place where you have to reach the top, and the other is a combination of Casino Night Zone from Sonic 2 and the Special Stages of Sonic 1.
-EXCELLENT MUSIC HERE! I'd forgotten how awesome S&K's music actually is, and is overall a step up from Sonic 3's. None are bad here and they seem closer to Sonic 2's soundtrack, especially the Flying Battery, Sky Sanctuary, and Death Egg themes.
-THE ZONES ARE VARIED FROM PREVIOUS GAMES. Yes, there is another volcano zone, but now you can explore new areas like the massive tombs of Sandopolis, the flying ruins of Sky Sanctuary, and the inner sanctums of the giant Death Egg ship. Plus now you get to take out the giant Flying Battery ship which attacked you near the beginning of Sonic 3. Strangely, this seems to be the only Sonic game without a water zone, which renders the Bubble shield useless, but oh well. In contrast, you will find more use out of the fire shield though.
-PERHAPS THE BEST FINAL BOSSES OF ANY SONIC GAME. There are a bunch of them to take out near the end, and when you collect all the chaos emeralds, you can go through a special Doomsday Zone as Super Sonic. Plus, Knuckles has more difficult versions and some original bosses of his own to fight, so it never gets boring.
-Since this is technically the other half of Sonic 3, THERE ISN'T A WHOLE LOT OF NEW STUFF FOR SONIC'S ADVENTURE. Pretty much Sonic has all the same attacks, animations, and powerups as in Sonic 3, and now with Tails gone, his reaching abilities are hindered. His absence is fixed, however, by locking it onto Sonic 3.
-THE SAVE FEATURE FROM SONIC 3 IS SORELY MISSED. With as massive as the levels are, being able to save after Sandopolis Zone Act 2 would be nice, but again, this problem is remedied after locking it onto Sonic 3.
-NO CHANGE OF SPECIAL STAGES HERE. Basically, these new ones are simply styled after the Sonic 3 SS's.
Don't let the 4 stars deter you at all. S&K is certainly one of the most memorable Sonic games of all, and if you liked Sonic 3, then I see no reason for you NOT to like this one. As a whole, Sonic 3 & Knuckles deserves its full 5 stars, so whether you want to find their original carts, or just play them on PC or the new Sonic Mega Collection, find them any way you can because these are some of the best 2D games that defined an age of gaming. GOTTA JUICE!