• Mushroom Hill -- A lush forest full of, that's right, mushrooms of all shapes and sizes. Jump on the freaky fungi for a boost up. Home to Butterdroid (Tefutefu), Cluckoid (Kekou), Mushmeanie (Hidoun), Madmole (Mogumogu), and Dragonfly (Tonbaa).
• Flying Battery -- It's Robotnik's airship, but unlike Wing Fortress, this one's mostly on the inside. Home to Blaster (Bonbon) and Technosqueek (Chu-chu).
• Sandopolis -- It's a big, nasty Egyptian-style desert at sunset. Act 1's not too bad on the outside world, but Act 2 finds you playing 2D Tomb Raider inside a pyramid. Find a switch to flick on the lights, but it never lasts long, growing consistently darker until you pull the next light switch...which wouldn't be so bad if there weren't these darn ghosts gaining strength with every increasing shade of darkness. The clock, once again, turns out to be your worst enemy in this massive Zone. Home to Sandworm (Naaru) and Skorp.
• Lava Reef -- It's into the heart of the volcano, and Act 1 gets pretty steamy. Things cool down in Act 2 to reveal some hidden ruins sprinkled into the stony walls. Home to Toxomister (Puwazoon [Poison?]) and Fireworm (Anbaa).
• Hidden Palace -- It's just a dinky little area with no enemies and a few sets of spikes as the only obstacle. At the end, though, comes the showdown with Knuckles followed by Robotnik's big move on the Master Emerald.
• Sky Sanctuary -- Up those crumbling ruins in the sky! A greatly modified Silver Sonic returns to make your day miserable with a couple of classic boss fights: the ball-swinging machine from Green Hill and the duplicate-producing Metropolis machine. For the final battle he performs all his same tricks from Sonic 2, only now you've got Rings at your advantage. Home to EggRobo. (As Knuckles, this area consists of a couple of boss fights, including Super Silver Sonic.)
• Death Egg -- Finally get to see what this Death Egg thing we've been hearing about since Sonic 2 is. And it's BIG. Act 1 is played on the inside while Act 2 is on the outside. Act 2 has some serious gravity issues... Home to Spikebonker (Gaatei) and Chainspike (Kurou). (This Zone is only playable as Sonic and Tails, unless you use the cheaty level-select.)
• Doomsday -- It's the ultimate showdown: Super Sonic (or Hyper Sonic) against a fleeing Robotnik in his giant Eggman mech. The stage: outer space, against a meteor shower...cool! (This level is only playable as Sonic, and only if you've obtained at least seven Chaos Emeralds.)

   One big enhancement is the addition of two new bonus stages: the Slot Machine bonus and the Glowing Spheres bonus. The Slot Machine bonus opens up when you hit a Starpost with 20-35 Rings. (It's denoted by an orange Star Circle.) It's a blast from the past inside: they work on the same schema as the original Sonic 1 Special Stages. You're in a 360° rotating maze, complete with Rings, bumpers, and GOAL spheres. Right smack in the middle, there's a slot machine...pop in and make a match to score (or lose) some Rings.

   He's done pinball, he's done slot machines, now Sonic does pachinko courtesy of the Glowing Spheres bonus, which opens up when you hit a Starpost with 35-50 Rings (denoted by a red Star Circle). The object is to grab all the gusto you can get on your journey upward, while keeping one step ahead of the laser teleport crawling up the bottom. You'll find the same "bubble" items as in Sonic 3's gumball machine bonus, plus Rings and large glowing spheres which act like hedgehog magnets. There are also flippers on the sides and various bumpers scattered around the middle.

   There are also seven brand new Special Stages following the Sonic 3 formula...and they're even tougher than the first set. New to the mix are yellow spheres, which act like springs and send you flying ahead five squares.

   When playing S&K alone, you can choose to play as either Sonic or Knuckles. Although the levels they play are mostly the same, each has access to certain areas and bosses the other can't reach. It should also be noted that while Knuckles' game is shorter, it's much more difficult. Sonic's got the exact same set of moves sported in Sonic 3, while Knuckles has his own unique abilities: gliding and climbing. Too bad his jump is somewhat shorter than Sonic and Tails'...

   Okay, that's all good and well, but the real beauty of S&K comes when you pop open the top and suggestively "Lock-On" another game. Stick Sonic 3 up there, and you get Sonic 3 & Knuckles...the real deal, baby! Thirty-two whopping megs of Sonic goodness. When locked-on with Sonic 3, you can use 3's save feature (which is absent from the stand-alone S&K)...with two added slots, making a total of eight game saves (which turned out to be just enough for me, ya know). Also, now you can play as Knuckles in the Sonic 3 levels and Tails in the S&K levels! All three characters have access to their own unique areas the others cannot reach. You'll also note that some of the object placement in the Sonic 3 levels has changed slightly. Oh, and don't worry if you've already got a cleared Sonic 3 save...lock S&K on and you'll find your save ready to roll in Mushroom Hill!

   Then there's the Special Stages...obtain all seven Chaos Emeralds in Sonic 3, then Lock-On to S&K to gain access to the Super Emerald stages. You lose all your Chaos Emeralds (and your ability to transform into Super Sonic), but your reward for collecting all seven Super Emeralds is even greater: Sonic becomes Hyper Sonic, Knuckles becomes Hyper Knuckles, and even Tails becomes Super Tails. As Hyper Sonic, you've got the Hyper Dash, which is like a double-jump that also destroys all the Badniks on-screen. Every time Hyper Knuckles claws into the side of a platform, the screen quakes and all the on-screen baddies go bye-bye. Super Tails gets the assistance of four Super Flickies, who track and destroy any Badniks in the vicinity. Sweet!

   There's even more goodness to be had when you pop yer old Sonic 2 cart on top: you can now play as Knuckles in all the Sonic 2 levels! Aw yeah, that's what I'm talkin' about! You'll find some new items at odd places that only Knuckles can reach, so it pays to explore the nooks and crannies you could never get to before. (But what the HECK is up with the gray shields?)

   Hey, the fun don't end there! Pop on just about any Sega Genesis cartridge in existence and you'll gain access to a randomly-generated S3&K-style Special Stage! You get an extra special treat when you Lock-On the original Sonic 1: unlimited randomly-generated Special Stages! And they're even harder than the original fourteen. (Dear God, have mercy.) Now that's what I call some serious-ass bang for the buck.