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Sonic 3 & Knuckles bug list

From Sonic Retro

This is a list of bugs, glitches, etc. that have been found in the locked-on game Sonic 3 & Knuckles.

Some of these issues have been addressed in Tiddles’s fan-made ROM hack of S3&K entitled Sonic 3 Complete; this is noted where applicable.

Contents

General bugs

Mid-boss music for main boss fight

The game will occasionally play the mid boss music for the main boss.

No Music for Act 2

At the end of the score tally, the music can sometimes simply disappear if you get a specific amount of points. This because the jingle for getting an extra life interrupts the music for the next act to start.

Mid-boss monitors

A couple of interesting things can be done with the monitors that show up after a boss fight:

  • If you destroy a ring-monitor right before the score tally comes up, your ring counter will show the right amount of rings, but you will only gain the amount of points of the rings you had before destroying it.
  • If you destroy a bubble-shield monitor at the right time, it will cancel out the music for the next act.
  • As they bounce out of the ground, if you were to get under them they can either crush you or push you into the ground.

Slope Glitch

There are several circumstances in which Sonic or any other character can achieve a sort of ‘zero gravity’ mode whereby he can walk in the air, without fallling (as he should) until he jumps. He keeps walking at the angle of whichever platform he was on when the state was triggered and will not be able to walk at another angle without jumping again. With this mode, Sonic can pass through any floor or wall and reach areas that are normally unreachable without debug as long as you can find an enough angled floor to build momentum from.

Circumstances where Sonic can achieve this state include:

  • In Carnival Night Zone, if Tails puts Sonic into the cannon, Tails will enter the cannon whereas Sonic will not. If Sonic spindashes on the cannon and releases it at the right time, he’ll enter the zero-gravity state.
  • In IceCap Zone, if Tails breaks an ice cube while Sonic is standing on it or if he touches the ice that is broken by the platform in the first infinite tunnel.
  • Launch Base Zone; and
  • In Flying Battery zone, if Tails brings Sonic to one of the hangers or if a character stands next to the spring on the mid-boss as it is dying.

Explanation: This glitch happens because the plus $08 flag at the RAM address $B02A (whose purpose is to stop Sonic from falling through objects) is not reset to normal after Sonic leaves the object on which he is standing. When Sonic stands on another object, destroys an enemy from above, or enters a bonus/special stage, the flag is properly reset to normal and the glitch thereby stops.

Zipping

Not actually a glitch as it's just the mechanics working as intended, but is abusable enough to warrant it listed here

Whenever you get inside a wall that is solid at the sides, trying to run in one direction will cause the character to quickly "zip" the other way. The actual speed you obtain is variable, depending on your position in the wall and the distance to the edge of the tile and it is likely an intended mechanic to avoid having players getting stuck in walls.

The kind of speeds obtainable with zips, between 16 and 32 pixels per frame, are fast enough to clip through other objects or even through the left boundary of the stage which usually is called level wrapping or horizontal underflow.

Zipping can only be done while standing.

Horizontal Underflow/Level Wrapping

Character position is stored with hex values and while the game has "physical" restrictions to stop you from under- or overflowing the position value, this can be overcome by having enough speed when running towards one of the stage endpoints to avoid the hit-detection.

Depending on the level, there's a large or small "loopback area" which basically is a glitchy repeat of the level. There are no objects placed here, but triggers based on the "camera" position still work.

When doing a wrap, the "camera" will rush towards the other end of the act in order to try and catch your character. If a "camera" triggered event that locks the screen occurs, such as a boss fight, your character will teleport to the nearest edge, even if it's right inside a wall. If your vertical position is higher than the locked position, the character will just fall back into the map and if it's lower, the game will behave as if you fell into a bottomless pit and you'll die.

Camera Manipulation

There's a couple of ways to manipulate the camera. This can be abused since objects are only loaded when they're on-screen. Different objects can be loaded at different distances from the camera however. Some examples include springs and spiked crushers in Lava Reef that are loaded approximately 1.1-1.4 screen-lengths away (which makes sense as springs should work even if you're running or rolling so fast that you go slightly ahead of the camera and the crushers because their moving cycle timer only start when they're loaded) and general obstacles like rocks and spikes which are unloaded as soon as they're offscreen.

The methods most commonly used are:

  • Crouching and jumping above the screen in stages that loop vertically. These include Marble Garden 1, IceCap 1 and Sandopolis 2. Interestingly enough it can also be used to manipulate the vertical screen locks in Sky Sanctuary and go from the bottom of the stage to the top of the stage instantly as the stage technically loops at one point in order to fit the height of it.
  • Spindashing. If a character comes with a high velocity towards a wall or an object, comes to a quick stop and then quickly spindashes; the screen will be displaced proportionately to how fast the character was travelling previously and how quickly he stopped and later spindashed. If done correctly, most solid objects that blocks the path of a character can be bypassed by doing this including the ones blocking off Knuckles path in Marble Garden 2, IceCap 1 and Launch Base 2.
  • By looking up or down and get hit or having Tails carry you. The screen is locked in position after being interrupted in relation to the character until he stands on flat ground. This allows for clipping through objects above, below and on walls.
  • By Flash jumping as Sonic. Flash jumping defaults Sonics speed to 8 pixels per frame while also briefly locking the camera and thus it's possiblew to go trough objects and sometimes solids.

Move during end-of-level score tally

If a player times it right and jumps into Tails’ hands as he is flying at the end of the level, the player will still be able to move during the score tally.

Knuckles can hover in Hydrocity and Sandopolis

If you climb in Hydrocity Zone below one of those up and down moving rotating blocks, it will push you down without resetting you to normal status when you leave the wall, resulting you are climbing in the middle of nowhere. This video might explain it a little bit better.
The same thing can happen in Sandopolis Zone

Knuckles’s different versions have difference colours of skin and socks

(This may not be a bug per sé but is documented here for posterity.) The player character and non-player character versions of Knuckles use different colours, presumably due to palette limitations (of some type). This is most easily demonstrated by entering Sky Sanctuary Zone act 1 as Knuckles through debug mode. The two ‘versions’ of Knuckles have slightly different hues; the computer-controlled one is more pink than red. Also, Knuckles’s socks change colours depending on his role: when you are playing as Knuckles, they are green; whereas when you are playing as Sonic, Tails, or Sonic and Tails, they are yellow.

  • Fan-made ROM hack Sonic 3 Complete now has optional IPS patches that allow the player to apply one or the other of these colours schemes to all versions of Knuckles, both playable and computer-controlled.

Glitches specific to Hyper Sonic

Hyper Sonic’s extraordinary abilities help to bring even more bugs and glitches into Sonic 3 & Knuckles. In particular, his double jump, which allows him to boost towards any of the eight main directions, can bring quite a lot of confusion to the mix.

Breaking scrolling for the Mushroom Hill Zone boss

By double jumping before the screen gets locked vertically, Hyper Sonic messes up the level’s scrolling. The level is still completable, though.

Level-specific bugs

Angel Island

Move during the intro cutscene

During the Knuckles cutscene, Tails still has control and can start carrying Sonic. Depending on what frame you reach a certain point, different graphical glitches can occur. Some even permanent until you reset the game or load the next act. If you're alone you can still observe placeholder sprites for the Monkey Dude and a couple flowers.

Clipping into the ground

In the first loop on the low path, right before the waterfall, if you do a frame perfect jump and roll, you can clip into the ground. Zip to the left to fall out of bounds and die or right and jump to get out.

Sonic in Knuckles path or vice versa

By jumping at a specific height with the right speed, all characters can clip into the wall right above the blocks. However, there's an area (not an object) that kills Sonic and Tails on contact Video. To avoid this, Sonic has to lock the camera above him and have Tails clip him through the spikes to the right, just before the boss. Once inside, wait for Tails to respawn and have him carry you over the solidity to your right. Position yourself about at the end of the slope and jump to fall down and survive the deadly area. The boss then spawns like usual and act 2 loads normally, but the level boundaries will be set for Sonic instead for Knuckles and thus Sonic will be unable to continue on this path.

For Knuckles to get up to Sonic's path, be hyper Knuckles and do a precise glide from just under the spikes to the other wall.

Getting back to the regular stage after the last tube

For whatever reason, there's chunks with floor just above the camera, just about before the cutscene is triggered. If you land on them you can jump up to the cliff on the left and quite simply run back, though there are a couple of places with floors and a waterfall chunk you have to jump over. Video

Other Oddities

  • When the first Fire breather escapes, his hurtbox disappears but his hitbox for the flames remains.
  • Depending on your speed when you enter the tubes, you can be slowed down or even roll all the way back to the entrance by pure chance. Sometimes you can even jump out of them which might save time in a time attack. This is especially noticable at the last tube in the end of act 2 since new sprites have been loaded for the cutscene with the bomber.
  • The crumbling platforms can sometimes be passed through by a bounce with a bubble shield for a single frame. This unlike e.g. Hydrocity Zone where you can pass through at any time after they begin to crumble or Lava Reef Zone where you have wait a specific amount of time.
  • By remaining in control of Sonic at the end of act 2 it is possible to entirely skip the Knuckles cutscene and fall straight down the Hydrocity Zone.

Hydrocity Zone

Palette Swap

When you go through the underwater tube right at the start, the screen flash and the game changes palette. If you proceed to get back to the very first area where you fall down (easiest with Tails) you'll see how the formerly blue underwater tiles now is a very bright orange. If you go through the tube again there'll be no water jet coming out.

Ramp Glitch

Sometimes when running up 90 degree ramps, you'll clip into it and fall through inside the wall. Video

Getting through the solidity of edges

By very precisely jumping into a corner and bouncing with a bubble shield, it is possible to go inside the walls of the level and take shortcuts etc. Tails can simply fly into them as he can't land when his y-velocity is larger or equal to zero. If then your x-velocity is zero when your y-velocity reaches zero or less, the game simply lets you fall through the bottom if you're not close enough to the top.

Moving Wall Glitch

At the beginning of act 2 when the left wall begins to move. If you're right next to the wall at the right place (slightly before the checkpoint) jump at a certain height (about where the rings are) and do an insta-shield or start to fly while holding right, the moving wall will clip you into the ground. Since the act transition was vertical, certain special boundaries are in place in order to prevent you from getting back into act 1 and thus a horizontal underflow is impossible unless the stage was loaded from fresh (i.e. level select, special stage or death). Video

Blue Ramp Glitch

The blue ramps only have solidity upwards, which means that if you jump towards them you can pass through them as long as your y-velocity is directed upwards. If you do get behind one, you can then go to the base where it meets the floor and you will sink in. Do a couple of spindashes right here and you're lodged in the floor and can zip left and right. If you're coming from above, their solidity blocks are only 16 pixels large at any given spot (relatively small), so if you can get a y-velocity higher than that then you have a chance of clipping through too. Video

Marble Garden

Act 2 Boss in Act 1

Since this is a stage that wraps vertically, you can despawn the object that kills in the mudpits and since they're not solid from above it's safe to jump down right before the act 1 boss and zip past it to enter the loopback area. If you get here and try to beat the act "again" you'll eventually end up to an area that spawns the act 2 boss inside a wall. It's only possible to get to the next stage with Sonic alone or Knuckles though as the game will mess up with Tails otherwise. It's also necessary to go down the lower path and then crouch at the part where the rectangular platforms usually get lowered into, otherwise it'll be impossible to break the capsule after. Then you can't get hit or jump at the right side of the screen so you have to find a good spot on the left side to attack the boss on. Finally to prevent a softlock or a death, you have to jump out of the wall at a certain place on the left side. Video

Knuckles vs. Sonic's Boss

Go to the place where Knuckles can't continue on Sonic's path because he can't jump high enough to hit the Relief. Get a spinning top and balance it into the small room where it resides, grab a hold of one of the walls and hit his jewel three times by jumping back and forth. Proceed with the level as usual until you get to the boss.

Sonic/Tails vs. Knuckles' Boss

Get Sonic or Tails to the top left corner of the whole stage, right where the Mantis is. If you don't have a friend to help you and you don't want to play as Tails, it's most easily done by taking a spinning top to the top lefternmost corner you usually can get to and simply jump over the top. Once there, spindash by the edge and let go in such a way that you won't drop too much after the moving platform. This should get you enough speed to go over the top again in which case you can drop down right by the pillar and zip left to do a horizontal overflow. You're on the lower part of a hill in the loopback now so spindash up and if necessary jump with the right timing to avoid death and you'll be at Knuckles boss. Video

Carnival Night Zone

Wheel Glitch

In Carnival Night Zone, if a character lands on one of the three ring boxes under the the first wheel in the stage without breaking them, the standard wheel physics will continue to apply even if you're on normal ground. What this means is that the gravity is set to a high and fixed value (i.e. no acceleration) and also that the gravity is to be applied downwards from sonics current perspective, no matter which direction that might be. E.g. if you'd run up a halfpipe you'd start falling to the side feet first. Video

Barrel Clip

By getting a bubble shield in act 2 and bouncing on a barrel in motion, it's very easy to clip into walls.

Despawning Capsule

By taking Sonic's route, the capsule at the end of Knuckles' stage have been known to despawn. This which means that in order to complete the stage, he has to climb up and face Sonic's boss which nothing is stopping you from to do. After that the cannon and stage transition works like normal even as Knuckles.

Loopback Area from the right side

While playing as Knuckles, one can take Sonic's path in Carnival Night 2, then glide over the boss area revealing The loopback area.

Mushroom Hill Zone

Act 2 boss sometimes shows as Dr. Robotnik rather than Eggrobo

Sometimes, Knuckles’s boss will have the face of Dr. Robotnik rather than Eggrobo as it should. This usually happens after the player loses a life, because it’s caused by the game’s not having sufficient time during reloading to patch-in Eggrobo’s face over Robotnik’s.

Not fixed in any version

This was fixed in the fan-made hack Sonic 3 Complete.

Flying Battery Zone

Knuckles fights Robotnik instead of Eggrobo

While playing as Knuckles in Flying Battery Zone’s second Act, the boss is Dr. Robotnik instead of Eggrobo. Unlike the above bug, this occurs every time.

This is likely to be due to the game’s artists missing this sprite. The battle's perspective is different – the Eggpod and therefore its pilot face the screen head on – and thus requires new sprites, which the artists did not implement for Eggrobo.

Not fixed in any version

The fan-made hack Sonic 3 Complete addressed this by implementing Eggrobo sprites edited from one of the ending cutscenes.)

Lava Reef Zone

Tails uses the wrong animation while falling with Knuckles’s boulder

When Knuckles throws the boulder at the end of the second act of Lava Reef Zone, Tails will use the wrong animation – facing sideways and rotating, rather than his ‘hurt’ sprite – if he’s not playing alongside Sonic.

Exploding Iwamodoki shows 100 points but does not award them

The badnik Iwamodoki releases a small animal and displays a “100” points score when it explodes, but it does not award points to the player. Perhaps the lack of points – but, of course not the presence of the score notification – is intentional because the player cannot be directly responsible for destroying the badnik, which instead self-destructs when a character approaches. This might indicate that Iwamodoki was supposed to behave like Asteron, which upon self-destructing neither awards points, displays a notification, nor releases an animal.

Launch Base Zone

Sonic can fight Knuckles’s boss in Act 1

If Sonic passes through the set of spikes near the start and under a collapsing platform and a huge rotating cylinder, he will zip to the right and arrive at Knuckles’ boss arena. Two Twin Hammers will appear, but Sonic only needs to defeat 1 to proceed to the next level. However, Tails must lift Sonic to the ledge on top of the arena to avoid death when the next level loads. Sonic mustn’t defeat both bosses at the same time, or the game will crash. The undefeated Twin Hammer can be destroyed without worrying about the game crashing; otherwise, it will follow Sonic wherever he goes. It can get quite annoying.

Failing to rotate on rotating floors

If the player’s character comes to a natural stop on the spinning floors after being rolled up into a ball, he will be using his standing sprite instead of the rotating sprites.

Triggering the booster infinite times

If the player does a Spin Dash in the right place and at the right time, the character will trigger the booster for an infinite number of times, as long as he maintains his charge of the spin dash.


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