From Sonic Retro
Knuckles' Chaotix (カオティクス) is a "Sonic"-related game for the ill-fated 32X expansion to the Mega Drive/Genesis. It features Vector the Crocodile, Charmy Bee, Espio the Chameleon and Mighty the Armadillo, along with Knuckles the Echidna, Dr. Eggman, and Metal Sonic to provide a link to the Sonic universe. Other characters include Bomb the Mechanic and Heavy the Mechanic, who are booby prize characters in the character select screen. The game doesn't feature Sonic or Tails (except in the best ending with both in the Tornado), although evidence suggests they were meant to be playable characters at one point (see Sonic Crackers and Knuckles' Chaotix Prototype 1207).
Some elements of the game have been re-used in later games with Espio, Vector, and Charmy returning to the series in 2004's Sonic Heroes. Also, the concept of a player controlling two characters is reused for Sonic Advance 3.
Due to the game being much longer than most Sonic games at the time, the game was given a battery-backup save feature which allowed the player to save their progress either manually (by going past the exit sign) or automatically (your progress is immediately saved after you beat an act/special stage).
On a side note, all of the badniks and almost all of the bosses in the game use gray, power sapped rings to function rather than animals. However, the rings cannot be collected like regular rings, as they dissolve not long after falling out of their badnik/boss machine. This concept was later used for Tails Adventure's and Sonic Advance 3's robots, but the rings appear to be fine when released and can be collected like any other ring.
According the game's Japanese manual, a mysterious island rose from the sea shortly after the events of Sonic & Knuckles. Doctor Eggman discovered the island, and found a mysterious ring inscribed with descriptions of the Chaos Rings, ancient Rings infused with Chaos Emerald energy. In order to find these Rings, Eggman built his base, the Newtrogic High Zone, on the island. Mighty the Armadillo, Espio the Chameleon, Vector the Crocodile, and Charmy Bee also arrived at the island, and ended up being captured by Eggman and Metal Sonic, and placed in Eggman's Combi Catcher machine. Knuckles, curious about the strange island, goes there as well, and manages to rescue Espio. The two then go on to stop Eggman from getting the Chaos Rings.
The story provided by the Western manual, however, was completely different. In it, Knuckles guards Carnival Island, a large hi-tech amusement park. Dr. Robotnik goes there to steal the power emerald that powers the whole island so he can use it to power his evil devices. Dr. Robotnik traps Vector the Crocodile, Charmy Bee, and Mighty the Armadillo, who were visiting the island, in the Combi Confiner (a machine Robotnik built that freezes them in time) and is about to do the same to Espio the Chameleon until Knuckles chases him away. Knuckles then discovers that he can rescue one friend at a time using ring power, which holds the two partners together like a rubber band. All the characters (plus Heavy the Robot and Bomb the Bomb) then work together to save Carnival Island from Robotnik.
The primary objective of the game remains unchanged from previous Sonic titles. The player must finish each level in under ten minutes and defeat Dr. Robotnik's badniks along the way. Rings still constitute the player's life energy and can be collected to enter special stages. Extra lives are unobtainable in the game (Due to the fact that you don't really have "Lives" to begin with) — once the player is damaged when he has no rings and his partner is absent (if you have no rings, getting hit will temporarily cause you to lose your partner, but he will return eventually) or if you use 'recall' to reduce your ring counter to negative 99 rings or lower, you will automatically be taken back to the world lobby (or back to the title screen, if you are in Isolated Island) and be given a chance to leave/save or to choose a different partner and/or try to choose another attraction to play.
The main game is divided into five worlds (called "attractions" in the game), each one consisting of five different stages. The stages are set in different times of day (morning, day, evening, night). The time of day is determined by how long you stay in the previous stage (if there was no change, then next time there will definitely be a change). The time of day effects enemy placements and boss difficulty. At the end of Level 5, the player confronts Dr. Robotnik in one of his contraptions.
The most fundamental change in Knuckles' Chaotix is the special ring force bond between characters. In earlier Sonic games, two-player mode would consist either of a traditional split screen race or a joint single player effort with Tails as a secondary character. In the latter case, this meant that Tails could move off screen and get lost for a few seconds until he returned to Sonic.
In Chaotix, however, both players are at all times connected on one single screen while neither player acts as the dominant force to move the game forward. Besides the staple of traditional Sonic moves and individual abilities this means some new tricks can be executed with the elastic force of the ring bond. For example, player 1 can hold his position while player 2 (or the AI, if in single-player mode) runs forward and stretches the bond to gain maximum speed. In mid-air the bond can be used to generate an upward momentum. Additionally, players can toss each other toward platforms or use the 'recall' button to reunite (at a cost of ten rings, even going into a negative count if necessary).
Consequently, damage is a bit more complicated. If an AI character is hit, only one ring is lost; if a human player's character is hit, behavior depends on whether or not he has picked up a Combine Ring (blue ring monitor). If the player has a Combine Ring, the lost rings will come out as one big ring, giving him ten seconds to get that ring and reclaim all your rings before it breaks apart. If he doesn't have it, then he loses all his rings.
Knuckles' Chaotix saw one of the most expansive item repertoires in Sonic history, as well as the most one-game items in the series' history.
Executive Producer: Mamoru Shigeta
Game Designer: Hiroshi Fukutsu (quest), Keisuke Miura, Kenichi Ono
Chief Graphic Designer: Takumi Miyake
Chief Programmer: Hiroshi Okamoto, Toshiaki Yajima
Sound Director: Tatsuya Kouzaki
Original Sound Version Recordings
See Knuckles' Chaotix OSV for a download page.