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Sonic the Hedgehog 2 (16-bit)/Bugs

From Sonic Retro

Player bugs

Super Sonic at the end of a level

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Attempting to transform into Super Sonic after hitting a signpost or prison capsule results in Sonic "walking" in mid air, and becoming unresponsive to controls. If Sonic moves off the right side of the screen before this happens the score tally will appear and the game continues on to the the next level as normal. If he does not leave the screen he will get stuck with no way of ending the level.

The player can't wait for a time over, because passing a signpost stops the timer. The only thing to do without debug in this situation is to reset the game.

Note: Prison capsules make the score tally appear automatically, so the level will always end.

Fixed in Rev.02.


Above water speed underwater

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If Sonic Transforms underwater he'll have his above water speed.

Not fixed in any version.


Tails high score

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If Tails hits an enemy after Sonic has just died, he gets stuck and gains a large score (as well as several extra lives).

This bug occurs in all known betas and prototypes; an easy way to reproduce it in the Simon Wai prototype is to go to Hidden Palace Zone, immediately Spin Dash to the right, and press jump as Sonic dies.

In the final, the bug still exists, but Tails starts flying when Sonic dies, making him unable to hit enemies.

Fixed in Rev.00.


Super Sonic countdown

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The timer that keeps track of the ring countdown is flawed in that it cycles every 61 frames instead of 60. This effectively gives the player an additional second of time for every 60 rings.

Not fixed in any version.


Incorrect palettes as Super Sonic

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Sonic2 MD SuperSonicShield.png


Graphics which share Sonic and Tails' palette line are affected by the transformation into Super Sonic, meaning Flickys and shield monitors will also glow yellow.

Partially fixed in Knuckles the Echidna in Sonic the Hedgehog 2: Knuckles' affect on the palette is more devastating to the game due to his green socks. Monitors are changed to use greys so are not affected by super palettes, though Flickys will still glow.


Life counter glitch

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If a player dies from time-over in a 2P Versus mode while on their last life, the Game Over routine will be interrupted and the results screen will be displayed. The player who died will appear to have 0 lives, but if they die again, the counter will roll back to "y5" (255), as the lives are stored as an unsigned byte, and the life counter was only meant to display up to 99 lives.

This bug can also be found in single player mode. In Chemical Plant Zone, there is an area before the boss where there are spikes underwater. If a player has 1 life, gets a ring and lets the drowning timer dwindle down to "1", then jumps into the spikes, Sonic will drown in the middle of his "recoil from damage" animation, which will cause two lives to be lost and the counter to roll back to "y5".

Not fixed in any version.


Multiple Badniks in a row in 2-Player mode

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It's quite common knowledge that if you destroy several badniks in a row you're awarded more and more points.

However, this behaviour is present also in Sonic 2's 2-Player mode, and the counter of destroyed badniks is shared between the players. Example: If Sonic destroys a badnik, and Tails quickly destroys another badnik, Tails will get 200 points, and vice-versa. First noticed
Sonic Retro
here
.

Not fixed in any version.


Level bugs

Emerald Hill Zone

Title card

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One frame of the title card does not draw correctly. This phenomenon is unique to Emerald Hill Zone, and does not appear in earlier prototypes (it became an issue in beta 5).

Not fixed in any version.


Horizontal scrolling glitch

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In Emerald Hill Zone, the bottom two rows of foreground pixels don't scroll horizontally, causing them to be permanently misaligned.

This was fixed in both Knuckles in Sonic the Hedgehog 2 and 3D Sonic the Hedgehog 2, but no versions of the vanilla game.

Not fixed in any version.


2P: Bridge sprite glitch

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In 2P VS mode, if you go on the top route to the section where there's two bridges right next to each other and move the camera such that only four or fewer logs from the first bridge are visible, the entire first bridge will disappear. The bridge will reappear if you move to the left again.

Not fixed in any version.


Chemical Plant Zone

Falling into a tube

Sonic2 MD CPZ Act1TubeFall1.png
Fall down a tube...
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...and you'll end up in strange places.


Should you get knocked into a transportation tube by getting hurt, Sonic and Tails will not enter their spin animations and will fall through the scenery. The game will correct itself, however, as every time the duo are meant to change direction in the tube, they will be moved to their intended positions.

Not fixed in any version.


Avoid boss attacks by ducking

Sonic2 MD CPZ Act2BossDuck.png


While fighting Water Eggman, Sonic can avoid being damaged by falling chemicals by ducking. It is not known if this is an intended gameplay feature - the same rules do not apply to Tails (or Knuckles).

Not fixed in any version.


Aquatic Ruin Zone

Corrupted waterfall tiles

Sonic2 MD Comparison ARZ Act1Waterfall.png


The animated tiles below the surface of waterfalls are corrupted, with noticeable gaps every 16 pixels. This was not always the case, as evidenced earlier prototypes of the game.

Not fixed in any version.


Enemy collision

S2 ARZ Leaf Collision Bug.png
Sonic gets hit by a Grounder, but nothing happens!
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Disabling the scroll plane to get a closer look.


If Sonic touches an enemy while he's in a section of the level that is obscured by leaves, no collision will occur.

Not fixed in any version.


Boss totem poles

Sonic2 ARZ BossEndBug.png


Eggman is easy to beat if the player climbs up on top of one of the totem poles. These totem poles are not lowered until the player who lands the final blow on Eggman hits the floor.

If Sonic is standing on top of a totem pole and Tails lands the final blow, Sonic will be left hovering when Tails hits the floor. The same glitch can be triggered with Sonic and Tails' roles reversed. This is only likely to happen if a second player is controlling Tails - the computer will usually spend the fight getting hit by arrows.

Not fixed in any version.


Hill Top Zone

Rexon crash

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On Hill Top Zone, it is possible to crash the game when hitting Rexon (the plesiosaur-like badnik that sits in the lava). Conflicts in the code cause it to jump to a section of code it was never meant to jump to. This results in invalid opcodes being processed and an eventual crash. This was fixed in Knuckles in Sonic 2.

Not fixed in any version.


Super Sonic death

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When playing as Super Sonic, if he enters the area where the Rexon from above is found and falls to the bottom of the screen (where there is lava) then the camera doesn't follow him quick enough, the ring-loss chime plays and Sonic dies.

Not fixed in any version.


Oil Ocean Zone physics

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In Oil Ocean Zone Act 2, find the area with four green platforms which launch into the air occasionally. Step on the last one and when being shot out of the tube hold right and land on the spikes in a way that will knock you into the round object to the left. If done correctly the physics will be different and the character will jump higher. The bug eventually wears off when getting in another speed tube, jumping on a spring, or passing through a wall. Alternatively, you can use the Pro Action Replay code FFB82C:0004 while on that level. This code only works when reaching that area.

Not fixed in any version.


Metropolis Zone shortcut

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By triggering the platforms that fall into the lava while invincible (even via getting hit) Sonic will ride the platform and penetrate the lava. This almost always brings Sonic into a later part of the level. With one platform that isn't far from an invincibility box, you can even get the "zero-gravity" mode.

Not fixed in any version.


Sky Chase Zone falling off of Tornado

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In Sky Chase Zone, if you charge a spindash up and release, you will go too fast for the Tornado and fall off. This also happens with Super Sonic, too. Whether or not this is actually a glitch is up for debate, as it could just be seen as a mistake on the player's part.

REV02 "fixes" this by changing 2 lines of code.

This possible bug, also exists in the 2013 Remake.

Fixed in Rev.02.


Wing Fortress Zone walking on air

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In Wing Fortress Zone, find a column of platforms that rise up and then retract. Stay on one of the platform as it reaches the top and retracts. You won't fall down and instead will be standing in mid-air. You can walk left and right at that height and won't fall down until you get hit by an obstacle or jump down.

This is only present in the Sonic Classics version of Sonic 2.

Fixed in REV00 and REV01.


Miscellaneous bugs

Sonic's sprites

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Two sprites which are Sonic's black and white transformation and Super Sonic walking are aligned wrong.

Not fixed in any version.


Invisible blocks in Debug Mode

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In versions prior to REV01 invisible blocks and yellow spring walls were visible in Debug Mode.

Not fixed in any version.


Thomas Kalinske typo

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REV00
Sonic2 MD Bug ThomasKalinske.png
REV01


In the credits, former Sega of America president Thomas Kalinske is misspelt as "Tohmas Kalinske".

Fixed in REV01.


Debug Mode Crash

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Placing an object in Debug Mode after dying causes the game to crash due to a word operation at an odd address.

REV00 actually tries to prevent this but the code it goes to has the command along with a branch.

REV01 has a better location but removes a command.

Not fixed in any version.


Over 999 rings

Sonic2 MD Bug 999RingsMonitor.png


Sonic 2 is meant to max out its ring count at 999, however Super Ring monitors will still attempt award the player 10 rings. This leads to Sonic and Tails having ":09" rings.

The ring bonus is still calculated correctly should you finish with this amount, acknowledging that the player has over 1000 rings.

Fixed in REV01.


Water level title cards

Sonic2 MD Bug TitleCardWater 1.png
Sonic2 MD Bug TitleCardWater 2.png
Sonic2 MD Bug TitleCardWater 3.png


If the zone about to be entered contains water, the title card will use its underwater palette for one frame as the level loads. This even applies to Hidden Palace Zone if you force your way in through hacking.

Not fixed in any version.


2P title cards

Sonic2 MD Bug 2PAct2Load1.png
Sonic2 MD Bug 2PAct2Load2.png


The border separating the two halves of 2P mode isn't just there for show - it allows the game to execute code during the screen draw. During the title card sequence, this border fluctuates as the level loading code can't execute fast enough (and even during gameplay it is not a perfectly straight line).

Act 2 takes this to new heights, briefly rendering remnants of Act 1 and even failing to render the top half of the screen for one frame.

Not fixed in any version.


2P teleporters

Sonic2 MD Bug 2PTeleport.png


When breaking the teleport monitor, player graphics appear are corrupt for a few frames until the camera adjusts itself.

Fixed in REV01.


14 continues chime

When the 14 continues cheat is performed by playing sounds 01, 01, 02, and 04 on the options menu, an invalid sound attempts to play, resulting in non-stop Oil Ocean music for the remainder of the game. The fault is with the way the sound number is entered into the game's code. For every sound, the bit 7 must be enabled to properly reference it. The code instead is written without bit 7 being used.

Fixed in Rev.02.


Music tempo change

If the 1-up jingle is playing while the Power Sneakers wear off, the level music will not revert back to its normal tempo.

Not fixed in any version.


Unlimited Power Sneakers

If a player dies whilst using Power Sneakers in 2 player mode, the character's speed level isn't reset properly, thus causing the character to run at Power Sneaker-speed for the remainder of the Act.

Not fixed in any version.


Super Sonic keeps invincibility stars

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When transforming into Super Sonic, if Sonic collects his 50th ring and jumps while invincible, the invincibility stars will not disappear after 20 seconds as expected. Since Super Sonic is already invincible, the stars don't give him any additional powers.

Not fixed in any version.


Passed star post

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First, go to a Special Stage normally. Then go to the star post on a small island (use a spring to get up) and you will see that it has already been lit, and you didn't pass it at all.

Not fixed in any version.


Super Sonic in 2-player mode

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If you get all the Chaos Emeralds (it doesn't matter if you use the cheat code or get them manually), go to the title screen, go to the OPTIONS menu, then press Start while on the VS MODE ITEMS option, 2 player mode will start and Sonic can turn Super, though he has glitched graphics. The animation frames regular Sonic has (like looking up or jumping) are unaffected.

When you die, you'll come back as Super Sonic with zero rings, giving you about 1 second to remain "Super". Before Sonic's camera catches up to his respawn point, you can also use the other player to see Super Sonic just standing there.

If you make Sonic turn super and hit a teleport monitor, Sonic will turn back to normal, and Tails will inherit several 'Super traits', effectively becoming "Super Tails": He has no flashing palette or trailing stars, but he does inherit Super Sonic's speed and invincibility. He also gains invincibility stars.

The game will only reset your Emeralds to 0 when you select 1 or 2 player from the title screen. You can get the Emeralds with one character, go to the OPTIONS menu, select another character, and automatically have the Chaos Emeralds.

Not fixed in any version.


Sonic's arm disappearing

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On the title screen, Sonic's arm disappears for a single frame.

Not fixed in any version.


References


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