Knuckles' Chaotix, in Japan called simply Chaotix, is a platform game in the Sonic the Hedgehog series, developed by Sega of Japan rather than Sonic Team, and published by Sega for the Sega 32X. The game was released in North America in March 1995, in Japan on April 21, 1995 and finally in Europe in May 1995. Despite demand from fans, the game's only "re-release" has been through GameTap's PC service. It was originally going to be in Sonic Gems Collection but it was not included for unknown reasons (possibly emulation issues). However, an entire section of the museum of Sonic Gems Collection is dedicated to this game. It is the only Sonic-related game to be released for the Sega 32X and its stand out features include its 2D sprite-based graphics and simultaneous two player gameplay.
Tomorrow's the big opening day for Carnival Island, a huge amusement resort with the latest in high-tech rides and games. As guardian of the island, it's Knuckles' job to make sure nothing goes wrong before the grand event.
Unfortunately, the evil Dr. Robotnik has other plans. He needs fuel for his latest diabolical device, and the Power Emerald that supplies electricity to the entire island fits the bill perfectly. His awful new invention, the Combi Confiner, should help him get rid of that annoying echidna and his friends.
When Knuckles returns from patrolling the far end of the island, he discovers that Dr. Robotnik has imprisoned all of his friends- Espio the Chameleon, Mighty the Armadillo, Vector the Crocodile and Charmy Bee. After he chases the Doctor off, Knuckles discovers that he can rescue one friend at a time by using Ring Power... only the power that sparks between the rings holds the two partners together like a magical rubber band. Never held back for long, Knuckles finds that with a little teamwork, he can use the stretching and snapping action of the Ring Power to double- even triple- the partners' speed.
And they need all the speed they can get. As Dr. Robotnik drains the power from Carnival Island, everything on the island begins to break down! Robotnik must be stopped, or by tomorrow morning - the morning of Carnival Island's big opening day - the grand amusement park will lie in ruins!
Each character in Knuckles' Chaotix has his own special abilities. Knuckles still glides and climbs as he did in Sonic & Knuckles. Espio has the ability to walk upright on walls and ceilings, and instead of curling up into a ball when performing the spin dash, he twists into a tornado, and can destroy unguarded enemies by running headlong into them at full speed. Mighty is the fastest runner in the game, and he has the ability to scale walls with his feet and push himself upward. Vector is the largest member of Chaotix. His moves include a mid-air dash and the ability to climb on walls. Charmy, finally, is the smallest character in the game but his ability to fly gives him a definite edge over the other characters.
Aside from Knuckles and his friends, the game also introduces Heavy & Bomb, two robots who claim to have escaped from Dr. Robotnik's evil clutches, and want to help team Chaotix. Heavy & Bomb cannot be selected from the character select screen, but instead are picked up through the combi catcher. Neither of the two robots can attack. Just as his name says, Heavy is heavy and slow, yet he is indestructible and has the ability to destroy enemies and monitors by simply walking against them. Bomb on the other hand is tiny and quick, but he explodes when he's hit, hurting friend and foe alike. Both of these characters can only be playable directly if the Stage Select is activated through the game's Color Test. They can also be played as normally in Special Stages if the player has one of them as their partner and throws them into the Special Stage ring.
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-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-effectively making your partner an 'extra hit point' for the players sake) 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 when this happens, which is also only possible through using recall, due to lack of hazardous obstacles or enemies in that level) and be given a chance to leave/save or to choose a different partner and/or try to choose another attraction to play.
The levels are divided into five worlds (called "attractions" in the game), each one consisting of five different levels in which every two stages/acts played, change to a specific time of the day (morning, day, sunset, and night). 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 (and what eventually became one of the most criticized features of the game) involves 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 Knuckles' 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 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 call-button to reunite (at a cost of ten rings, which meant that for the first and only time the ring count could dip below zero in a Sonic game). Also, in two player mode if either player is hit without a shield/invincibility/big ring (a item that when obtained, causes you to lose all of your rings in the form of one, slightly larger than usual ring temporarily if you are hit) they lose all of their rings (which is not the case in single player mode, when if the partner is hit, he only loses one ring instead of all of them).
Recently, some elements of the game have received new life with Espio, Vector, and Charmy returning to the series as of 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, and they dissolve not long after falling out of their badnik/boss machine. This concept was later used for Sonic Advance 3
Also, Sonic Advance had a special stage similar in concept to this bonus stage, but the only things that can be found are rings, spike balls, and Chaos Emeralds.
Special stages can only be accessed through a single large ring at the ending of each level, but the player must have collected at least 50 rings for it to appear. After a player wins all six Chaos Rings, the special stages start over in a wireframe mode.