Emerald Hill
Emerald Hill features all the luxuries found in most holiday resorts: sun, sea, rolling hills, waterfalls and psychopathic killer robots. No swimming pools though, I'm afraid. Being the first port of call for the game, there's nothing too challenging here. Run through the loop-de-loops while admiring the scenery, but watch out for concealed spikes and the roaming enemies… Further exploration reveals some fake walls that lead to extra lives and such.
Chemical Plant
A death trap full of toxic chemicals – No, not the local fast food chain, it's Eggman's Chemical plant! Get around using the high-speed tubes and dodge the traps and pitfalls. The main hazards in this zone is the poisonous goop called Mega Mack (Hmm… Maybe it is your local fast food chain after all...).
Aquatic Ruin
Built by a rather unfortunate ancient civilisation, these ruins suffered from a little water damage… That is to say they're completely submerged. The high ground is littered with arrow firing totem poles and the low ground features falling debris. Underwater, keep moving and grab air bubbles and you'll make it through. Stick to high ground wherever possible, and Sonic'll probably appreciate it.
Casino Night
The first in a long line of Casinos that the speedy duo have visited, Casino Night has bumpers, flippers and slot machines - the whole zone acts as a kind of giant pinball table (You can almost hear Sonic's chiropractor shout in joy). Run past the neon lights and rack up points and rings on the pinball tables… Just don't warp young Tails' mind - we don't want him developing a gambling problem now, do we?
Hill Top
The fresh mountain air will do you a world of good, but the fresh noxious lava fumes probably won't. Teeter-totters with flame-less Ghoras launch you into the air and scale the rock faces, and Green Hill-style S-bends launch you off at speed. Lava pits are dotted across the zone, so stay light-footed. Watch out for the large cave in act 2 - there'll be a large quake that causes the lava below to rise. Jump to the top and you'll be able to escape.
Mystic Cave
This deep, dank, dark cave is infested with creepy-crawly robots and deep pits. The good news is these pits aren't bottomless. The bad news is the bottoms of the pits are lined with spikes. Pull switches to drop bridges and open new areas, just keep your wits (and your bug-spray) about you.
Oil Ocean
Eggman's rather lax attitude on preservation comes into play here - he has an oil refinery plant over the sea, and it ain't all that refined. Zoom across slippery catwalks and use air vents shoot you to higher platforms. Don't sink into the sludgy ocean and you might make it through the zone alive. Not clean, but alive.
Metropolis
This huge sprawling zone is like a mechanical maze. Spinning cylinders, pounding pistons and rotating gears make this place difficult to get around, not to mention the most devious robot in the game is waiting to knock you off screw-lifts!
Sky Chase
Sonic and Tails take to the skies on the Tornado, chasing Eggman's Wing Fortress. Sonic, shirking such outdated principals like sitting or sanity, opts for some unaided wing walking. Or rather, wing standing and jumping. Here, you can run around like usual, even move up and down, but the Tornado moves around under you. Still, don't run too fast or you'll have to be scraped off the floor.
Wing Fortress
Here, Sonic (or Tails, if you're playing as him) goes it alone and explores Eggman's aerial fortress. Watch out for the severe lack of floor in certain areas, not to mention being shot out into the open sky with nothing but some loose tiles on the side of the base to grab onto.
Death Egg
This is it, the final zone. But it's quiet… too quiet. Well, not really – background music is playing like usual, but there are no enemies to be seen. Move forward, and you'll be face to face with a rather larger, eviller and shiner Sonic – Mechanical Sonic. But that's not all…
Special Zone
In special stages, you run down a chute collecting rings and avoiding bombs. You need to collect a certain amount of rings before reaching a checkpoint. Rings are spread out over the stage, and to collect them you need to run around the walls and ceilings. Bombs also litter the stages. Touching bombs, as perhaps you may have guessed, isn't really a good thing. It causes you drop many rings, making it more difficult to pass checkpoints. If you get to the end of the stage you blag yourself a Chaos Emerald, taking you one step closer to getting the game's true ending. Each stage gets progressively harder, with less rings and more bombs. Much like in real life.
  

Emerald Hill
Here, Eggman comes at you in a car with a drill attached (it's an optional extra, like the CD player). He simply drives left to right, so avoid the front and hit him eight times. After the seventh hit, he'll fire the drill piece at you, but one hit more and he's done. I wonder if his insurance covers being attacked by hedgehogs of foxes...
Chemical Plant
This time Eggman has the arena set up - he sucks up the Mega Mack from below and attempts to drop it on you. Avoid it, and the moving outer floor, and hit him eight times. Stick to the middle of the stage and you should be OK - the floor stays put there.
Aquatic Ruin
Here Eggman employs some common knowledge - Hitting totem poles with a hammer cause them to fire an arrow at you. Of course. Avoid the arrows from the bird beaks and use them to jump up on top of the poles. Hit Eggman when he comes by, but avoid the hammer. Again, eight hits does it.
Casino Night
Eggman's set up a huge pinball table for you to duke it out in... Shame you're the ball. Manoeuvre yourself to hit Eggman from above to avoid the electricity flowing below his Egg Mobile, and watch out for the bombs he drops - they split into four bits of shrapnel. Hit him eight times and he's outta there.
Hill Top
Here Eggman has a flame-throwing gun on his Egg Mobile. He rises from one of two lava pools, fires it and then submerges again. Thing is, in doing so, he launches two fireballs which ignite the two platforms nearest to the pool. Jump to the other side, and hit him two or three times when he appears. Eight hits fries his egg.
Mystic Cave
Now Eggman's taken up construction work - putting a large drill on his Egg Mobile and tearing up the boss arena! When Eggman disappears in the ceiling, he causes an earthquake that sends down loads of rubble. The normal rocks are fine, but there are spiked stalactites that can do damage, so stay on your toes. Eggman will then drop back down, and move the other side of the arena, drills facing forward. When he does this, take the opportunity to hit him. You should be able to get two hits in before he goes back up and the cycle starts again. at least Eight hits and he's licked.
Oil Ocean
Eggman's ship now sports a laser cannon, and he ain't afraid to use it. The arena consists of two platforms on either side of the screen, and an oil pool in the middle. The laser rises above and fires three shots at you, going from high to low shots, with the lowest shot skimming the bottom of the platform you're on. Jump or duck out of the way of the cannon, and it'll return to the oil pool. Watch out for a spiked tail that shoots out from the murky depths, too. Eggman then surfaces from the middle, which is your opportunity to hit him two or three times. Repeat this for eight hits and you're the winner.
Metropolis
Now Eggman's coming at you with a bunch of seven balloons around hit ship - They spin around him preventing you from getting a clear shot at him. Avoid the balloons and eventually he'll send them out from around his ship to fill the arena. When he does this, take your opportunity to hit him. Once hit, he looses a balloon and it turns into a small Eggman balloon (trippy, eh?). Hit the balloon to pop it and avoid it hitting you. It gets easier to hit him as he looses his balloons, and when they're gone after seven hits, he fires lasers from the front of his craft. Avoid these and hit him one more time to beat him.
Wing Fortress Zone
When you enter the stage, two lasers either side of the arena activate, trapping you. A larger laser moves around in the centre of the arena, while three spiked platforms bounce around. Jump onto the platforms, making sure you don't touch the bottom or collide with any of the others, then hit the laser when it emerges form it's metal casing. It takes a while before it charges up, so you can hit it two or three times before it activates. Avoid the beam and do the same again. Eight hits does it.
Death Egg
Mechanical Sonic: First up is a robot version of Sonic to beat, Mechanical Sonic (Mecha Sonic for short), and you'll have to do it without any rings. This guy first comes down on the right of the screen, standing still. Jump on the front part of his head to avoid the buzz saw spikes. His attacks include spinning across the floor or jumping from one side of the screen. His other attack is a kind of dash along two lengths of the screen. You can also hit him at this point, as long as you avoid his back. Watch out, as eventually he'll jump and fire spikes across the screen, which is hard to avoid. Eight hits and you've gone and beaten the original ‘faker'.

The Ultimate Guide To Mecha Sonic
Here's the order of his moves, starting from the right side of the screen:
1. Spin across floor. <-
2. Standing dash to the right, then back to the left.
3. Jump ->
4. Spin <-
5. Spin ->
6. Jump <- with spikes shooting
7. Dash
8. Jump ->
9. Spin <-
10. Spin ->
11. Jump <-
12. Spin ->
13, Dash
14, Spin <-
15. Jump ->
16. Jump <- with spikes shooting
Repeat from 1, but with the directions switched, since you're starting on the left.

See the tricks section for info on beating Mecha Sonic with style.

Final boss: The final boss is Eggman in a huge mech, in his own rather obtuse image. The machine's only weak point is its head, which is too high up to hit normally. It sports two spiked arms that it can shoot at you, and a massive jump attack. End up behind him and he'll fire several Eggman bombs at you, which split into four fireballs when they explode. When he jumps up into the air, run to the far side of the stage and watch the target that appears over you. When it flashes red, quickly run to the centre of the stage. Eggman'll crash down, and bend over. Quickly run over and hit him in the nose. The first time he lands he then bends down again and fires his arms at you. The best way to avoid them is to run to the opposite side of the screen (this only works if you made him land in the other far side to start with). It's possible to hit him before he fires, but it's very risky. After firing, Eggman launches up again.

The next time he lands, Eggman will crouch then start to walk towards you. If there's enough room, you can easily avoid him. It is also possible to hit him while he walks, but you have to avoid his spiked hands, usually by jumping over them when they're low. If you're playing as Knuckles, who doesn't jump as high as Sonic and Tails, you can only hit him when he's crouching or by hitting him under his spiked hands, which is VERY hard. A whopping twelve hits and you've beaten Eggman once and for all (until the next game, that is)!