A Zone is the name used in early games of the Sonic the Hedgehog series to refer to the distinct playable levels. Each Zone is broken down into a number of "Acts". Most Zones have either two or three Acts, although some have one or four. Both Sonic games on the latest Nintendo consoles (Sonic Colors for the Wii and Sonic Lost World for the Wii U) have six acts and four acts respectively.
The term was used in this context in Sonic the Hedgehog, Sonic the Hedgehog 2, Sonic the Hedgehog 3, Sonic & Knuckles, Sonic 3D Blast, and others. (Sonic the Hedgehog CD changed the terminology somewhat, using "Rounds" in place of Zones and using the word "Zone" to refer to what was usually called an Act. Sonic Lost World also used the word "Zone" to what was usually called an Act.)
Each Zone usually has its own unique landscape, palette, and sprites, with its own set of enemies to defeat and obstacles to overcome. Each Zone divided into two or three Acts and at the end of the first few Acts is a Bonus Plate which marks the end of the act as well as grants a bonus depending what the post sign displays. The final act is usually shorter and ends with a boss fight (usually against Dr. Eggman in a machine of sorts). However, some Zones will have different appearances across their separate acts (for example, Act 3 of the Scrap Brain Zone in Sonic 1 resembles the earlier Labyrinth Zone unlike Scrap Brain's first two Acts). In Sonic Lost World, the Zones will have different atmospheres to their supposed theme (for example, Desert Ruins Act 1 will start in a desert area, while Act 3 will take place in a dessert themed area, with the name even changing to "Dessert" Ruins).
It is not clear within the games whether the name of the Zone also relates to the location where the level is set (in some instances, such as The Doomsday Zone, which takes place in space, it is quite clear that this is not the case), but in many cases, the name of the location is taken to be the same.
In Sonic the Hedgehog CD, all settings and levels in the Little Planet are seen used the term Round instead of Zone. This is seen in the game's instruction manuals and the secret Level Select menu, where all levels are titled such as "Round 1". Each Round has three acts, but the "act" as term has been now replaced with Zone and it is also implied in the Round's title card. This term shift has only been demonstrated in Sonic the Hedgehog CD.
In later games since Sonic Adventure and Sonic Adventure 2, Zones were replaced with Action Stages or just stages which were similar to Zones, but instead of divided into two or three acts, were single whole levels, most not ending with a boss fight (some were but as part of the story straight after the stage). While each of the stages were named, they were not "Zones" as in the locations names ended with "Zone". However, like the previous Zones, most stages had double-word names, but not ending with "Zone". Some Action Stages are in parts but not separate acts, simply getting through the entire stage to the goal. Also, the ending of the Action Stages do not have Bonus Plate at the end but giant Goal Ring. In Sonic Adventure it was originally Capsule or a Chaos Emerald if part of the story. While not normally in-game, instruction manuals stated using Action Stages in Sonic Advance games.
Another variety of Action Stage is not about going towards the goal but looking for three parts of a treasure. These stages are for treasure hunters like Knuckles or Rouge in which they usually search for pieces of the Master Emerald, however other items have been searched for like keys in Death Chamber and Chaos Emeralds in Security Hall.
In other media
Sonic the Comic
In Sonic the Comic, the term "Zone" is used much as it is in the games themselves. Specifically, the planet Mobius is broken down into continents, which are themselves broken down into Zones. Various stories also make it clear that many Zones operate independently of each other and that, with the exception of Doctor Robotnik's world-wide dictatorship that operates out of the Metropolis Zone, the Zones tend to govern themselves. (This makes them loosely comparable to real-world countries.)
In the Sonic the Hedgehog comic series and its spin-offs published by Archie Comics, the term Zone is mainly used to refer to one of a number of parallel existences. These include Mobius Prime (the home of Sonic and his friends), Moebius and the No Zone.
- Level (video game) at Wikipedia, the free encyclopedia.