Sonic Chaos

Sonic the Hedgehog Chaos is a video game for the Sega Master System and Sega Game Gear, developed by Aspect and published by Sega in 1993. It was the last platform based Sonic game released for the Master System in Europe. The Game Gear version was known as Sonic & Tails in Japan.

It was re-released in 2004 as an included game in Sonic Mega Collection Plus on the PlayStation 2, Xbox and PC, and is also included as an extra on Sonic Adventure DX: Director's Cut for the Nintendo GameCube and PC. To unlock the game, the player has to collect 60 emblems as all of the playable characters. All these re-releases are the Game Gear version.

Sonic Chaos is notable for the fact that it is the first 8-bit Sonic title to feature Tails as a playable character, and also the first in the series to allow the player to manually control his flight.

Storyline
The storyline to Sonic Chaos, like most Sonic stories, revolves around Dr. Robotnik and his quest for world domination via the use of the mysterious Chaos Emeralds to create nuclear bombs and laser weapons (according to the English instruction manual).

Robotnik has stolen the Red Chaos Emerald, causing the other emeralds to "lose balance", and warp themselves into the Special Zone. As a result, South Island is now sinking into the ocean, and it is up to Sonic and Tails to save the island and foil Robotnik's plans once again.

Gameplay
Overall, the gameplay is similar to previous 8-bit Sonic games. However, as stated above, players can control Tails as well as Sonic this time. Sonic now comes equipped with the Spin Dash attack, performed by holding the directional pad down to crouch and pressing action to gain stationary speed. When the down button is released he shoots forward curled in a ball, hurting any badniks that he comes in contact with while in this state (spikes and other obstacles do, however, still hurt).

By holding up instead of down, and then pressing action, Sonic will start running in place. By releasing up he will then zip forward in a running fashion, moving faster than the Spin Dash allows him to. This is called the Strike Dash, which is also in Sonic CD (known as the Super Peel Out in that game, and therefore this move is usually referred to under that title). However, Sonic will quickly stop unless the directional pad is held whichever way he was going. The big advantage to the strike dash is that he is invincible for a short distance, and "strikes" an enemy he passes through. However, one of the main disadvantages of the Strike Dash is that Sonic is vulnerable to enemy attacks after the brief invincibility wears off. Also, Sonic has more volition while rolling, so he does not slow down as quickly, but rolling uphill is more difficult than running uphill. This means the faster way to go downhill is the Spin Dash, but the faster way to go uphill is the Strike Dash. Sonic also has the job of finding the six Chaos Emeralds. Unlike other 8-bit Sonic games, the Chaos Emeralds are located in Special Stages. In order to enter a special stage, Sonic needs to collect 100 Rings in one act (you'll still be awarded the extra life for collecting 100 Rings). Sonic Chaos is also unique amongst all the Sonic games in that the special stages each have a different look. Challenges include flying towards an Emerald on rocket boots, hopping up various platforms on a spring, and navigating through a maze of pipes. Successfully complete the Special Stage to get a Chaos Emerald, but lose the Special Stage and Sonic goes straight to the next stage in the game as normal, without the emerald. Robotnik himself holds the sixth Chaos Emerald, and you need to beat him in order to win it back.

Playing as Tails is slightly different but generally easier. Not only can Tails fly (performed in the same way as Sonic's Strike Dash), but he starts the game with more lives and continues. Additionally, the player can not collect the Chaos Emeralds when playing as Tails; when he has 100 rings, he simply earns an extra life and the level continues. Tails can perform the Spin Dash in the same way Sonic can, and when he finds an item box that would normally contain rocket shoes, he gains a speed boost instead.

Zones
In total there are six stages to complete, each one consisting of three acts of which the final act is a boss battle.

In order, the Zones are:
 * 1) Turquoise Hill Zone
 * 2) Gigalopolis Zone
 * 3) Sleeping Egg Zone
 * 4) Mecha Green Hill Zone
 * 5) Aqua Planet Zone
 * 6) Electric Egg Zone

Bosses

 * 1) Lady Bug Boss (Turquoise Hill Zone)
 * 2) Bead Worm Boss (Gigalopolis Zone)
 * 3) Bouncy Boss Robot (Sleeping Egg Zone)
 * 4) Tree Crawler Boss (Mecha Green Hill Zone)
 * 5) Sphere-o-Bot Boss (Aqua Planet Zone)
 * 6) Laser Walker (Electric Egg Zone)

Music in the game
The background music for Mecha Green Hill Zone is a remix of the Green Hills Zone music in the previous 8-bit Sonic game, Sonic 2, which was also remixed into the main theme of Sonic CD: "Sonic - You Can Do Anything".

When accessing the Sound Test Feature in the game, "BGM#09BH" was a song that was never played through the entire game. Interestingly, it was later used in Sonic Triple Trouble as the Sunset Park Act 3 Song.

In addition, some music was altered or even changed completely for the Master System version.

Sequels
As a follow-up to Sonic the Hedgehog Chaos, Sega released Sonic Triple Trouble in 1994. The game was exclusive to the Game Gear console and entitled Sonic & Tails 2 in Japan.

Trivia

 * This is the first Game Gear/Master System game in which Tails is playable.
 * Since it wasn't possible for the player to make Tails fly in the earlier Mega Drive game Sonic the Hedgehog 2 (where he only was seen flying automatically to catch up with Sonic in the levels), this is the first game in which his flight can be controlled by the player.
 * This was the first game in the series to actually show how fast Sonic was moving through zones with a Km/h Speedometer sign post at the end of each act. Only two other Sonic games have adopted this: Sonic Labyrinth and Sonic Unleashed.
 * In the Master System version, Tails' name is written as "Miles Power" instead of "Miles Prower" during the credits' cast.