Sonic and Knuckles pick up precisely where Sonic the Hedgehog 3 left off. Sonic is thrown deep into the Mushroom Hills of Floating Island by the explosion from the Death Egg. Sonic knows Master Emerald, hidden someplace on Floating Island, and is confident that Dr. Robotnik desires it to provide his Death Egg lasting power. Knuckles most likely knows where it is, but will Sonic be able to stop Robotnik’s intentions and find Master Emerald while battling off Knuckles? Meanwhile, Knuckles is guarding Floating Island when one of Robotnik’s robots attacks him! He immediately begins his quest for vengeance.
Sonic & Knuckles is the fourth installment in the Sonic franchise. It keeps the same core characteristics as previous Sonic games (speed, rings for protection, Special Stages with Chaos Emeralds) and the three shield kinds introduced in Sonic 3 (Fire, Water, and Electric). Players can choose between the title characters, Sonic or the all-new Knuckles the Echidna. Knuckles cannot jump as high as Sonic but can glide in the air by holding the jump button. Knuckles will be able to climb a wall if you fly into it. He can also breach walls that Sonic cannot. Thanks to these talents, knuckles may access various regions than Sonic, giving each level an entirely new experience.
Unlike Sonic 3, Sonic & Knuckles has three additional levels, two of which can be obtained by jumping onto lamppost checkpoint stars (like in Sonic the Hedgehog 2). These stages allow you to gain bonus rings, lives, and power-ups. The first is a casino-themed level where you can enter a slot machine and earn (or lose!) rings. The second level is more skill-based, requiring you to time your jumps off orbs to launch higher and collect bonuses. It ends if you contact the barrier at the bottom of the stage. The other type of bonus stage is the “Special Stage” introduced in Sonic 3, which can be reached by jumping into giant rings hidden within the levels, as previously stated. The player will receive a Chaos Emerald if they collect all the blue spheres in these stages while avoiding all red ones.
The ability to “Lock-On” prior Sonic games into a cartridge slot at the top is a unique feature of the Sonic & Knuckles cart. By including Sonic 3, you can play both Sonic 3 and Sonic & Knuckles in one long game and save and use Tails in the Sonic & Knuckles levels. When Sonic 2 is plugged in, players can use Knuckles in Sonic 2 and his glide and wall climb abilities—finally, inserting the original Sonic the Hedgehog cart grants the player access to infinite level variations of the Blue Sphere bonus stage. These bonus features were also included in subsequent Sonic & Knuckles re-releases.
