Release the spin dash when he's finished and if you were facing away from him, you'll dash off safely to the opposite side.
When he passes by, he'll take a hit just by touching you, and another one when he turns around and dashes back from the other side. Just before he's about to dash, stand around the middle and face away from him, and charge up a spin dash of your own, but do not release it yet.
This can be tricky, and you'll die if you time it incorrectly, but there is an easier way. He isn't spinning in this instance, so you can hit his head twice here, if you can jump into it at the precise moments that he passes by you, on each dash. Another type of attack is where he'll use the wheels on his shoes to dash across from one side, and then turn around and dash back from the other side, without pausing in between. Follow the guide below to know which attack he's going to do, but if you're not sure, try standing in the far opposite side from where he starts, and jump over him and out of there when he arrives. Leap over him when he spins across the ground, and stand still in the center, below Eggman's window, when he jumps over you. He'll start spinning in a static position before moving. Mecha Sonic will usually be spinning in a ball across the room, either on the floor or with a jump in the middle. Notice that the window in the center of the room opens up once the mecha has landed, and Eggman is peering in, watching the action unfold. Your best chance is to know what he's going to do before he does it, and take every opportunity you can grab to hit him, because without any rings, every second counts.
Whoever he is though, with a set series of nasty moves that you need to learn and avoid, he's not just here for the free lunch. Perhaps a prototype for the more infamous Metal Sonic of Sonic CD, or others would argue that it would later be reborn in Sky Sanctuary Zone in Sonic & Knuckles. From the top right, something hovers down to the arena - a large grey robot modelled on Sonic! The first of our hero's robotic doppelgangers, often unofficially dubbed as "Silver Sonic", his actual name is probably closer to the slightly less original "Mecha Sonic". Anyway, the first boss room puts you against a dull brown technological background, with a straight floor as your battleground. Just as well, personally the odd wailing sounds that that track features thereafter isn't a favourite of mine, and it's almost as if the developers agree. A suitably space-like and very foreboding musical intro accompanies your entry, which is abruptly halted completely when you walk forward into the main room, where it is replaced by the boss music. First of all, you'll find yourself in a narrow corridor surrounded by light blue (Chemical Plant scenery art re-used) and brown coloured walls of technology and stars whizzing past in a window behind you. Eggman's massive mechanical spherical satellite of doom, poised to unleash deadly death rays on all living things from space, and it's up to you to bring down his evil schemes, save the planet and somehow survive the fall back down to home, eh? Well, we'll worry about that fall in a minute. It's been found that in the planning stages of the game, many more levels were considered, and you can find out a bit more about that in the Sonic 2 Beta section. Scenery graphics are improved and more detailed, and brand new environments are visited such as tall mountains and the caves within them, more varied factories and our first visit to the Death Egg space station. That's certainly not all you can expect from the stages though, as many of them continue the tradition with plenty of, or perhaps even more multiple routes, hidden shortcuts and secret areas, as well as varied and diverse traps and enemies. These kind of experiences are more common than slower paced, trap-filled corridors, as seen in the Marble or Labyrinth Zones in Sonic 1. One of the key selling points was that Sonic 2 is generally faster than its predecessor, and this is partly thanks to the level design, where stages such as Chemical Plant Zone feature long, twisting and looping stretches of ground to run along at great speed, creating some of the fastest experiences of the early Sonic world. You'll fight the boss at the end of each second act, and as with Sonic 1, Eggman strikes again in all new contraptions, each requiring eight hits to defeat.
They're long enough to enjoy them properly though, and somewhat easier too. Admittedly most of them are quite brief, and except for the later ones, each is divided into 2 acts, while Sonic 1 carried 3 acts per level. Sonic 2 is probably the biggest single 2D Sonic game so far, with a whopping ten levels (final boss stage not withstanding), as opposed to the average number of six or seven.