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 weapons and lasers (according to the U.S. version of the instruction manual).

Robotnik has stolen the Red Chaos Emerald, causing the other emeralds to "lose balance" and be transported to a parallel universe. 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 of world domination.

 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 inertia 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 each of the special stages takes a completely different form to the others. 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 zones to complete, each one consisting of three acts of which the final act is a boss battle.

• Turquoise Hill
• Gigalopolis
• Sleeping Egg
• Mecha Green Hill
• Aqua Planet
• Electric Egg

 Music in the game

Sonic in the final level, Electric Egg zone.

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. Also, for some odd reason when this game was ported from the Sega Master System to the Game Gear, the original music for 'Gigapolis Zone' was replaced with what many fans consider to be a completely inferior track of music.

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.