Special Stage

The Special Stages (also called Special Zones, and Secret Zones in the first game) are an important feature of the Sonic the Hedgehog video games. They are separate in location from the usual setting of those games (either Earth or Mobius), in which characters can find the mysterious Chaos Emeralds.

16-bit games
The Special Stages first appeared in Sonic the Hedgehog, in which it was depicted as a somewhat psychedelic rotating maze, with the Chaos Emerald ready for collection in the center, guarded by barriers. It was accessed through a giant Zone Ring, which appeared at the end of an Act if the player had collected 50 or more rings in that Act.

Sonic the Hedgehog 2 altered the game mechanics of the Special Stages, though the psychedelic backdrop remained the same. Whereas gameplay in the Special Stages in the first game had been similar to the original game, in this game it was a mini-game in which characters ran along a curving half-pipe tube, collecting gold rings while avoiding bombs, which would lose 10 rings. There were 3 sections, and a character had to collect a sufficient number of rings in each section to advance to the next. In Sonic the Hedgehog 2, the Special Stages were accessed via Star Posts, which had previously only been used as save-points.

Sonic CD saw the return of the first game's end-of-act Giant Rings. In these special stages, Sonic ran across a Mode 7 style track. To obtain the stage's Time Stone (the game's equivalent to Chaos Emeralds), Sonic had to destroy six UFOs hovering across the track within a time limit. Hazards like bear traps and water would often slow Sonic down or speed up the timer (or sometimes both). When time ran low, a seventh, differently-colored UFO would appear in the center of the stage; breaking this one would not count towards stage completion but would restore 30 seconds to the timer, giving the player more time to hunt down and destroy the remaining UFOs.

Sonic the Hedgehog 3 and Sonic & Knuckles once again returned to using Giant Rings as the entrance to the Special Stages. However, in these games, they were scattered throughout the acts rather than left at the end, so a player could play multiple Special Stages in each act. Once again, the format of the Special Stages changed. This time, the characters had to run along the surface of a planet-like sphere, collecting blue spheres and avoiding red ones. If locked onto each other, the games became Sonic 3 & Knuckles. After completing the Sonic the Hedgehog 3 part with all Chaos Emeralds, the giant rings in the Sonic & Knuckles part started flashing in the Emerald colors. If entered they took you to the Hidden Palace Zone, where you could enter the special stages.

The obscure 32X game Knuckles Chaotix featured a strange type of Special Stage. Though it had the same basic formula as the Special Stages of Sonic 2, it had many odd quirks that made it very different. Accessed in the same manner as Sonic the Hedgehog/Sonic CD, these stages featured a hexagonal tube that the player ran down. The player could run across all six sides of the tube. The object was to collect a certain number of Blue Spheres scattered across the tube in order to reach the Chaos Ring at the end. Unlike Sonic 2's Special Stages, reaching a checkpoint without having all the required Spheres would not end the stage, but would simply repeat the section. The catch was that your Ring count steadily depleted as you remained in the stage (in a manner similar to Super Sonic), and the stage would end once you ran out of rings. You could find some rings in the stages, but the primary source of rings was those you had brought into the Special Stage. This made Chaotix's Special Stages unique in the respect that the more rings you were carrying upon entering the Special Stage, the easier it was to successfully complete. However, no matter how many rings you held, if you fell out of the tube through one of the stage's many pits, the stage automatically ended.

8-bit games
In Sonic the Hedgehog and Sonic the Hedgehog 2 for the Game Gear and Master System, the special stages were to get extra lives. Sonic Chaos however featured a unique brand of Special Stage. Accessed simply by collecting 100 rings in the main game, the Stages were little more than labyrinthine versions of the game's main stages, with the Emerald hidden somewhere within. The player had to find the Emerald within a strict time limit. These stages are notorious for their difficulty; except for the first stage, in which the emerald is simply at the end of a long void crossed by using the game's Rocket Shoes, the emeralds were always hid in obscure or subtle ways, making it nearly impossible to find them without the aid of a game guide. Also, though the game featured Sonic and Tails as playable characters, only Sonic could access the Special Stages.

Sonic Triple Trouble's Special Stages were accessed by hitting an item monitor displaying a Chaos Emerald whilst carrying 50 or more rings. The game's five Special Stages came in two varieties: the first, third, and fifth were remarkably similar to those of Sonic Chaos, in which the player had to navigate a labyrinthine maze in order to reach the Emerald within 90 seconds. Though the Emeralds were hidden less obscurely than in Sonic Chaos, the mazes were much harder to navigate, as there were springs and invisible ledges that could only be crossed through a process of trial and error. The second and fourth stages featured Sonic/Tails in the series' trademark biplane, the Tornado, collecting 80 rings in a short flying course. These stages were remarkably easier than the 2D mazes. What sets this game's Special Stages apart from all others, however, is the fact that at the end of all but the first, the player had to fight a mini-boss in the form of Nack the Weasel (called Fang the Sniper in Japan). Usually, these battles were incredibly easy, as Nack always seemed to have no clue how to pilot the vehicles at his disposal. Unlike Sonic Chaos, both Sonic and Tails had access to these Special Stages.

Sonic Blast featured a rather horrid take on Sonic 2's Special Stages. Accessed by finding a giant ring hidden within the first and second acts of each zone (similar to Sonic 3/Sonic and Knuckles), the player had to navigate a short obstacle course, collecting 50 rings before reaching the end. Like Sonic Heroes, the first acts were for extra lives, while the second acts were for an Emerald. The problem with these stages lied in the awkward pseudo-3D perspective and the fact that there were hardly enough rings in the stage itself to meet the quota. Also, you only got one shot at each stage, so if you messed up, you couldn't retry the stage. This led several people to simply bypass this game's Special Stages.

In the Neo Geo Pocket game Sonic Pocket Adventure, the Special Stages are almost identical to that of Sonic 2 for the Mega Drive.

New games
Sonic Advance used Special Stages where the player's character fell down an apparently infinitely deep hole while standing on a board. The player had to collect rings and avoid bombs much like in Sonic 2, and there were also special rings that could boost your speed. The stages were accessed by finding a large hidden spring in each stage and jumping on it.

Sonic Advance 2 featured an odd take on Sonic CD's Special Stages. Taking place in the same Mode 7 style arenas as the aforementioned game, the player was required to collect 300 rings within 120 seconds. However, because each stage barely held that amount, the player was required to collect several rings in rapid succession; doing so would steadily raise a multiplier that would increase the worth of the collected rings (so a ring collected while the multiplier was at x4 would make that single ring worth 4). All the while, the player had to avoid Sonic Adventure's ZERO, who patrolled the stage and would cause the player to lose rings if he hit them. These stages were infamous not because of the stages themselves but because of the method of accessing them; the player had to collect seven Special Rings hidden in each act. These rings were often hidden in out-of-the-way locations, so finding them was almost impossible without the help of a strategy guide.

Sonic Advance 3's Special Stages were very similar to the ones from Sonic Advance, and also to the biplane stages from Sonic The Hedgehog 2. In the stages, the character is standing on the wings of Tails' biplane, the Tornado 2, which has to be flown around while the character walks back and forth in order for the character to collect a number of rings within a time limit. There are also special rings that transform the plane into its speedy X-shape, boosting forward quickly. To get to the Special Stages in Sonic Advance 3, one has to find all the hidden Chao scattered across each Zone's multiple stages, and once they are found also collect a special key that appears at a random location in any Act of the Zone. While the Chao are permanently stored, the keys can only be used once each and both dying or failing to collect the Chaos Emerald will mean that the key will have to be found again. The keys, once found, are used to activate the "golden springs" on each Zone's overworld, which boost the player off the top of the screen (it is assumed that these bi-plane Special Stages take place in the sky above the main Zones). After defeating G-Mel in Nonaggression, the game unlocks a 'Special Stage' mode, in which the object is to collect as many of the 7 Emeralds as possible.

Sonic Heroes marked the return of the Special Stages in a 3D Sonic game (as mentioned earlier, there are no Special Stages in Sonic Adventure and Sonic Adventure 2). The player needs to collect a Special Stage key (which is lost if you get damaged) in a particular stage to enter a Special Stage. Getting a Special Stage key in odd-numbered stages (Stage 01: Seaside Hill, Stage 03: Grand Metropolis, etc) opens up Bonus Challenges, where you try to beat the timer for points and 1-ups, linking spheres to add time to the clock. getting a Special Stage key for even-numbered stages (Stage 02: Ocean Palace, Stage 04: Power Plant, etc) opens up Emerald Challenges, where you race against time and chase for the Chaos Emerald, powering up the Power Dash by collecting spheres.

Sonic Rush had special stages similar to those of Sonic 2's where the player had to slide Sonic across the touch screen with the stylus to collect rings. If the player got enough rings before reching the half-way point, they would be given a higher ring count and would then have to collect that many by the end of the stage to obtain the Chaos Emerald. There were bombs in the stages that would cause the player to lose rings and had to be avoided, red plane-type enemies that also caused the player to lose rings if touched but could be destroyed for two rings. There was also a bat-like enemy that took 3 hits to defeat and stayed in a fixed position on the screen until it attacked. In addition, there were buttons on the ground that could be pressed to cause more rings to appear in the stage.

Outside the games
As the game lines gave little in the way of an explanation as to how such a strange dimension could exist, spin-off media and fans developed theories as to the nature of the Special Stages.

Fleetway's Sonic the Comic grouped the Special Stages into a single "Special Zone", depicted as a complete parallel universe, complete with planets and cities, although the bizarre cosmology of the games was adhered to. This Special Zone resembled Sonic's home planet of Mobius, even with similar anthropomorphic animal inhabitants, and the two planes had a great deal of communication due to the Star Posts and the intervention of the Omni-Viewer. The Special Zone's largest city was called New Tek City, capital of Planet Meridian, and it was protected by the Chaotix team. Notably, the UK fiction presents the Special Stages of the first Sonic game to be not a natural part of this universe, but a series of sub-orbital space warps created by Doctor Robotnik to keep the Chaos Emeralds out of Sonic's hands. In the fan-made Sonic the Comic-Online webcomic, the echidna scientist Dr. Zachary theorises that the Zone was formed by a Big Bang of excess Chaos energy from the formation of Mobius.