Sonic & Knuckles

Sonic & Knuckles (ソニック&ナックルズ) is a platform game in the Sonic the Hedgehog series, developed by American studio Sega Technical Institute in collaboration with Sonic Team, and published by Sega for the Sega Genesis/Mega Drive in 1994. It is the direct sequel to Sonic the Hedgehog 3, which was released earlier that year. The game features unique "lock-on technology" which enables another cartridge to be plugged in via the socket on top.

Gameplay

 * For a more detailed examination of gameplay, see Sonic the Hedgehog 3.

Gameplays focuses on Sonic and Knuckles, Knuckles not being playable in Sonic the Hedgehog 3 because Knuckles was against Sonic and Tails. In addition, Tails has now been removed from play. Essentially there are two separate games to tackle, depending on which character is selected at the start of the game. Although the appearance of the Zones is the same for either character, their layout and some of the bosses' tricks differs noticeably at a number of points in the game (especially noticeable difference is that Knuckles fights EggRobo, who has different and particularly smarter strategies). Zone differences increase starting from the Lava Reef Zone onwards. Style of play, however, does not differ significantly from one character to the next as it does, for example, in Sonic Adventure.

Despite no save file slots, gameplay is much expanded than in other games, as Sonic and Knuckles do not play all of the same levels. A significant difference between Sonic and Knuckles is that they don't have all of the same moves: Sonic can jump higher and run a little faster than Knuckles, and Sonic has the Insta-Shield, while Knuckles can climb walls and break through some of the blocked entry ways. While Sonic has the gift of speed, Knuckles can glide through the air with the greatest of ease.

As in Sonic the Hedgehog 3, there are two types of Stages: Bonus Stages and Special Stages. The Bonus Stages are entered by collecting at least 20 rings (or at least 50 to access the second Bonus Stage), and jumping through the bright ring of stars that appears above each checkpoint in the Zones. This time however, the gumball stage has been replaced by two new Bonus Stages. The first combines the slot machines of Sonic the Hedgehog 2 's Casino Night Zone and the 360° tumbling labyrinth Special Stage (to retrieve the Chaos Emeralds) of the first Sonic the Hedgehog. If three Robotniks appear on the slot machine, you lose 100 rings, or all your rings below 100. The second Bonus Stage is a large vertical course, with magnetic orbs that Sonic can use to propel himself upward. Along the way he can pick up shields, rings or lives. He is chased by a horizontal force field that slowly moves up and, when Sonic is caught in it, ends the stage, and reaching the top of the stage ends it as well.

Sonic and Knuckles' Abilities
Sonic the Hedgehog -- Runs slightly faster and jumps slightly higher than Knuckles. Sonic can use the W spin attack and all the special attacks associated with Barriers.

walk -- Push left or right on the D-pad to initiate Sonic's movement in either direction. As you hold the button down, Sonic gains speed.

run -- Begin walking and hold down the button to make Sonic gain speed. After a few seconds, he'll break into a run.

screech -- While running, quickly press and hold the opposite direction on the D-pad to make Sonic screech to a halt. He'll skid for a short distance, based on how fast he was moving.

look up -- While standing still, press up on the D-pad to make Sonic gaze to the heavens. As you hold up, the camera pans upward, giving you a view of Sonic's overhead surroundings.

crouch -- While standing still, press down on the D-pad to make Sonic duck. As you hold down, the camera pans downward, giving you a view of the stage beneath where Sonic stands.

spin -- While moving, press down on the D-pad to make Sonic curl into a rolling attack. He'll remain in this position until you jump or slow down. The speed of Sonic's movement while in spin form is based on how fast you're moving when you launch it, and also on the terrain Sonic rolls along.

spin jump -- Press A, B, or C at any time to make Sonic leap into the air with a spin attack. The height of the jump is proportional to how long you hold the button down.

push -- Certain objects can be pushed by running up against them. Continue holding the D-pad against the offending cube to have Sonic push it along the ground.

Super Spin Dash -- While crouching, tap any of the jump buttons to have Sonic rev up with a stationary spin. Keep tapping the jump buttons to build up momentum, and let go of the D-pad to dash off with a full speed rolling attack.

Insta-Shield -- Jump, then tap any of the action buttons while in midair to initiate a 360° slash that momentarily extends the radius of Sonic's spin attack.

Knuckles the Echidna -- Newcomer Knuckles is slower than Sonic and doesn't jump as high, but he can glide, climb, and punch through barriers Sonic would not be able to cross. Knuckles' game is shorter, but significantly more difficult than Sonic's.

walk -- Knuckles' basic movement. Push left or right on the D-pad to initiate Knuckles' movement in either direction. As you hold the button down, Knuckles gains speed.

run -- Begin walking and hold down the button to make Knuckles gain speed. After a few seconds, he'll break into a run.

screech -- While running, quickly press and hold the opposite direction on the D-pad to make Knuckles screech to a halt. He'll skid for a short distance, based on how fast he was moving.

look up -- While standing still, press up on the D-pad to make Knuckles gaze to the heavens. As you hold up, the camera pans upward, giving you a view of Knuckles' overhead surroundings.

crouch -- While standing still, press down on the D-pad to make Knuckles duck. As you hold down, the camera pans downward, giving you a view of the stage beneath where Knuckles stands.

spin -- While moving, press down on the D-pad to make Knuckles curl into a rolling attack. He'll remain in this position until you jump or slow down. The speed of Knuckles' movement while in spin form is based on how fast you're moving when you launch it, and also on the terrain Knuckles rolls along.

spin jump -- Press A, B, or C at any time to make Knuckles leap into the air with a spin attack. The height of the jump is proportional to how long you hold the button down.

push -- Certain objects can be pushed by running up against them. Continue holding the D-pad against the offending cube to have Knuckles push it along the ground.

Super Spin Dash -- While crouching, tap any of the jump buttons to have Knuckles rev up with a stationary spin. Keep tapping the jump buttons to build up momentum, and let go of the D-pad to dash off with a full speed rolling attack.

glide -- Jump and press any of the action buttons while in midair to have Knuckles glide slowly to the earth, extending the horizontal distance he would cover with a normal jump. The glide can also be used as an attack to destroy enemies.

climb -- Glide into a wall to have Knuckles latch on. Press up or down on the D-pad to scale the surface, and jump to let go.

Storyline
Sonic & Knuckles carries on from where Sonic the Hedgehog 3 left off. At the end of Sonic 3, after Dr. Robotnik's defeat at his Launch Base, the rebuilt Death Egg fell back onto Angel Island and crashed on top of Lava Reef's volcano (retconning the ending of Sonic 3, in which the Death Egg is apparently destroyed). Now the evil doctor attempts once again to repair the Death Egg, this time by trying to use the Master Emerald to fuel its engines. This all-powerful jewel, upon which the Chaos Emeralds base their powers, is guarded by Knuckles. Dr. Robotnik was able to fool the echidna into working for him and against Sonic. In Hidden Palace, he betrays Knuckles in order to obtain the Master Emerald. Knuckles then realizes that Dr. Robotnik has been playing him all along. Sonic, Tails, and Knuckles then reluctantly work together in order to stop Robotnik and save Angel Island. Later on, after the Island is brought to peace thanks to Sonic and Knuckles, an EggRobo is seen rising from the debris of Eggman's Death Egg. A few minutes after this event, Knuckles is seen chilling out in the hills of Angel Island. Suddenly, he is attacked by the EggRobo mentioned before. Knuckles becomes angry at the Robo and chases after him, beginning Knuckles's storyline in the game.

Levels

 * Mushroom Hill Zone: A Lush forest, with pump elevators, sticky vines, and filled with mushrooms that also serve as trampolines or parachutes. The miniboss is a woodcutter robot, and for the fight with Robotnik, the player must avoid the spiked bars and cannon shots while hitting the satellite-enhanced Egg Mobile.


 * Flying Battery Zone: The player is propelled to this flying fortress with electrified robots. The mini-boss looks like the Flicky-capsule and must be tricked into hitting itself. Robotnik is fought twice: first, he traps the player in an arena with a moving laser blaster on the ceiling, very similar to the Wing Fortress boss. Then, it goes to an exterior platform, to which Eggman latches onto from below and crawls along, spouting flame from the top of the pod everytime the character attempts to jump over, and swinging upwards to be hit.


 * Sandopolis Zone: The heroes fall in this desert zone, which houses a haunted pyramid which the character enters after beating the Guardian mini-boss. The boss, Egg Golem, must be hit in the face so Robotnik is exposed.


 * Lava Reef Zone: The insides of a volcano, on which the Death Egg had fallen. The miniboss consists of mechanical hands that hit the player and orbs that shoot fireballs. Knuckles doesn't face a boss, but Sonic faces Eggman in an invincible machine, which is only harmed by the landmines it drops.


 * Hidden Palace Zone: The old Echidna temple. Knuckles just traverses the zone. Sonic and/or Tails however, has to fight the guardian - Knuckles. After he is defeated, Robotnik steals the Master Emerald and causes Knuckles to help the heroes instead.


 * Sky Sanctuary Zone: A secret passage leads to these crumbly aerial ruins. Knuckles just faces his final boss, Mecha Sonic, which uses the Master Emerald to go Super. Sonic and/or Tails has to climb the zone facing Mecha Sonic four times - one in a flail-swinging Egg Mobile, another in a "Flying Eggman", and twice on foot.


 * Death Egg Zone: Robotnik's space station, with electric traps, a vacuum chamber and sections with altered gravity. Two minibosses - Red Eye, a vulnerable laser shooting eye surrounded by spiked orbs, and Death Ball, which is only hit when the rotating shield bumpers are away - before facing a Robotnik-shaped mecha, Kyodai Eggman Robo.


 * Doomsday Zone: Only accessible as Super Sonic, this zone has Sonic chasing Eggman through space, avoiding meteors and missiles, and trying not to get his rings depleted.

Lock-on Technology
Sonic & Knuckles utilizes "lock-on technology" that lets the cartridge plus the Genesis/Mega Drive access data from Sonic the Hedgehog 2 and Sonic the Hedgehog 3 so that elements of both Sonic & Knuckles and the locked-on game are combined. To play these combined games, the hatch on top of the Sonic & Knuckles cartridge can be flipped open and the second game placed inside.

The lock-on technology was actually a way of making up for the fact that the developers could not meet the deadline for Sonic 3. Originally, Sonic 3 was to be released with Knuckles as a playable character, and with all the Sonic & Knuckles levels playable (the level select screen in Sonic 3 features inaccessible Sonic & Knuckles levels and music for said levels can be played in the sound test). Time constraints forced them to split the project in two, releasing Sonic 3 with the completed levels and continuing work on the uncompleted ones, plus adding the Super Emeralds, and the lock-on feature. Indeed Sonic 2 had once run into similar problems, resulting in the original Hidden Palace and several other levels being removed.

Notably, no other video game in history features a "lock-on" feature quite like Sonic & Knuckles. Some NES games released by HES, as well as the Super Nintendo game Super 3D Noah's Ark, feature a cartridge port on the top to accept other games for the system, but this was purely to override the systems' respective lockout chips, as these games were not licensed by Nintendo. Some video game peripherals require being joined with a cartridge in a similar manner (i.e. Game Genie; GameShark), or transfer data between games (the Transfer Pak) but don't allow the "lock on"-style merging of data from 2 different video games.

Sonic the Hedgehog 3
Also known as Sonic 3 & Knuckles or Sonic 3 Complete Version, there are seven immediate differences:

Once the player picks a character and starts playing, more differences become apparent. Passing a star post can now open up all 3 Bonus Stages, including the slot machine stage (20-34 rings required), the magnetic orbs stage (35–49 rings required) from Sonic & Knuckles as well as the gumball machine (50–65 rings required) from Sonic 3. Knuckles' levels are different from Sonic's and Tails' in most cases, with new areas and bosses. There are slight differences in object placement in some of the Sonic 3 Zones as well (Launch Base in particular). Sonic and Tails skips the final boss of Launch Base, while Knuckles still has to do it (although he skips the first true boss of Launch Base). The Sonic & Knuckles levels are the same, except that Mushroom Hill now has an intro (Tails airlifts Sonic in).
 * 1) The player can play as Knuckles in the Sonic 3 levels.
 * 2) The player can play as Tails in the Sonic & Knuckles levels or have Tails follow Sonic throughout the entire game.
 * 3) After the levels of Sonic 3 are finished, the Death Egg was seen to fall intact instead of being destroyed, the play continues straight to the levels of  Sonic & Knuckles.  The final boss of Sonic 3 is also omitted for Sonic and Tails.
 * 4) Players must collect each Chaos Emerald before the correspondingly colored Super Emerald can be collected.
 * 5) Game progress can be saved in Sonic & Knuckles using Sonic 3  's save feature (there are now 8 rather than 6 save slots).
 * 6) Save slots now display information about the number of continues, lives, and the Chaos Emeralds surround the player's character as the player collects them (the Chaos Emeralds are replaced with the correspondingly colored Super Emeralds when the player collects them).
 * 7) The game uses Sonic & Knuckles  ' sound bank exclusively, which means that the songs that were different between Sonic 3 and Sonic & Knuckles (which include the title screen, 1-up, and invincibility sounds, as well as the mid-level boss music, Knuckles' theme and end credits theme) use only the Sonic & Knuckles version.

Collecting all the Chaos Emeralds in the levels of Sonic 3 will turn Sonic or Knuckles into Super Sonic or Super Knuckles. However, once the player enters their first Special Stage in Mushroom Hill Zone, they teleport to Hidden Palace where the Emeralds are taken from them and transformed into gray (apparently de-powered) Super Emeralds, thus beginning the Super Emerald quest. If the player does not have all of the Chaos Emeralds prior to reaching Mushroom Hill Zone, the acquired Chaos Emeralds will become Super Emeralds and the player is given the opportunity to acquire the first Super Emerald. However, the player will not be allowed to return to Hidden Palace via warp rings until they collect the remaining Chaos Emeralds. In addition, both Knuckles and Sonic can now go Hyper once they have obtained all of the Super Emeralds.

Tails cannot normally gain Emerald powers but does so when he collects all Super Emeralds, taking on the form of Super Tails. He has no Hyper form but simply remains Super, with four Super Flickies flying around him that attack nearby enemies. Taking care to avoid all the Special Stages, it is possible to finish the game with only the 7 Chaos Emeralds, retaining their Super powers until the very end of the game. In this case the game endings will resemble the good endings from Sonic & Knuckles. This allows for a total of nine different endings — each character (Sonic and Tails together have the same as Sonic alone) has one with 0–6 Chaos Emeralds, one with all 7 Chaos Emeralds and 0-6 Super Emeralds, and the third with all 14 Chaos and Super Emeralds.

Sonic the Hedgehog 2
Also known as Knuckles the Echidna in Sonic the Hedgehog 2 (or Knuckles in Sonic 2 for short), this game is identical to Sonic 2 (aside from a few changes to make it more playable with Knuckles) but with Knuckles now playable instead of Sonic or Tails. The title screen features Knuckles and the only option is "Press Start" (Options and the versus mode have been disabled). There are no new Zones. The only differences in gameplay are that Knuckles can explore once inaccessible areas (where secrets such as 1-ups have been added for Knuckles), some areas are harder because Knuckles cannot jump very high and accelerates slowly (in particular, the final boss is regarded as being much more difficult to beat while playing as Knuckles), the title cards (ex. Emerald Hill Zone Act 1) are green and red, and Knuckles retains his rings after a Special Stage, making it much easier to obtain Chaos Emeralds. Getting the Emeralds is easier too, for the Special Stages have reduced Ring quotas for Knuckles to achieve, making it much easier to obtain Super Knuckles.

Unlike the Sonic 3 lock-on, where the Sonic & Knuckles ROM referenced the data in Sonic 3 to add its additional features, this game used the Sonic 2 data bank exclusively except for an otherwise hidden extra data bank on the Sonic & Knuckles cart. The lack of knowledge over the existence of this patch made it impossible to find a working dump of the Knuckles in Sonic 2 ROM for a long time.

Sonic the Hedgehog
In the development of Sonic &amp; Knuckles, Sega attempted to implement Knuckles into the original game, but decided to leave him out. According to several programmers and hackers, the reason why Knuckles could not be placed into Sonic the Hedgehog like he was in Sonic 2 was that the palette colours of Knuckles' sprite would have, in fact, completely altered the palette scheme of the entire game. Therefore, instead of a Knuckles in Sonic 1 feature, fans were treated to a full version of the Blue Sphere game. Hackers, however, succeeded several years later in making a game hack called "Knuckles the Echidna in Sonic the Hedgehog." The colour palette problems are overcome by only using two shades of red for Knuckles' body, rather than four or five.

Any other Genesis/Mega Drive game
By placing the first Sonic game, or most other Genesis/Mega Drive games inside, a "No way? No way!" screen will pop up with Sonic, Tails, Knuckles, and Robotnik making odd faces, telling you the cartridge is supposedly incompatible. But, by pressing the A, B, and C buttons together, a minigame based on the Chaos Emerald bonus levels is unlocked, called Blue Sphere. There are over 100 million unique levels. The last level, "Special Stage", repeats itself once the level is beaten. Only by locking the original Sonic the Hedgehog or Sonic Compilation in the Sonic & Knuckles cart can one play through all the stages. The other Genesis/Mega Drive games will only play one level each, which will infinitely repeat. Despite being near randomly generated, the levels are playable for the most part, even if many bits and pieces of levels get recycled. On another note, some levels may be nearly impossible to complete while others are not as difficult.

In Sonic Jam and Sonic Mega Collection, the Blue Sphere game is playable as a separate game. Sonic Jam allows the player to access it by choosing to play Sonic & Knuckles and "lock it on" with Sonic 1. In Mega Collection, the game has to be unlocked separately. Additionally, there was a PC CD-ROM released, entitled Sonic & Knuckles Collection, that contained Sonic & Knuckles, Sonic 3, as well as the pre-combined version of the two games. This CD-ROM contained a full version of Blue Sphere.

Playing these levels via a game with a battery pack erases saved games. Additionally, games made after Sonic & Knuckles was released will not work with its lock-on feature. There are only a few games made before Sonic & Knuckles that do not work, such as Phantasy Star IV & the Mega Drive/Genesis port of Super Street Fighter II.

The reason that these games are unable to work with Sonic & Knuckles is that the combined size of the two games' data exceeds 4 megabytes, which is the maximum amount of memory that the Genesis/Mega Drive allots for game data.

Credits

 * Executive Producer: Hayao Nakayama
 * Producer / Lead Programmer: Yuji Naka
 * Director / Lead Game Designer: Hirokazu Yasuhara
 * Senior Game Designers: Hisayoshi Yoshida, Takashi Iizuka
 * Senior Programmers: Takahiro Hamano, Masanobu Yamamoto
 * Character Designer: Takashi Thomas Yuda
 * Scene Artists: Kunitake Aoki, Chie Yoshida, Tsuneko Aoki, Shigeru Okada, Takashi Thomas Yuda, Satoshi Yokokawa
 * Music Composers: Brad Buxer, Bobby Brooks, Darryl Ross, Geoff Grace, Doug Grigsby III, Scirocco, Howard Drossin
 * Sega Sound Team: Bo, Sachio Ogawa, Milpo, Masaru Setsumaru, Tatsuyuki Maeda, Tomonori Sawada, Masayuki Nagao, Jun Senoue