Sonic the Hedgehog 2 (Sega Master System, Game Gear)

Prototype Info Prerelease Info Bugs Version DifferencesA lot can change when porting to another console, then emulating it.

Level Select#

Master System#

While powering on the game, hold Left + 1 + 2 on Controller 2. When the intro sequence starts, release the buttons, then start the game as usual.

Game Gear#

When the intro starts, hold Down + Left + 1 + 2 + Start. When the title screen appears, wait for a ring sound to play twice (Tails will wink three times). Release all the buttons and press Start.

Unused Graphics#

Character Sprites#

Artwork	Name	Description
	"Crying Tails" Animation	Tails crying. Probably meant to be used in the ending cutscene when he is rescued.
	"Bored Sonic" Animation	While the majority of the game's Sonic graphics were copied from the Master System version of Sonic 1, the waiting animation was changed, rendering these three frames unused. They were used in the AutoDemo prototype, though.
	Sonic 1 Death Sprite	Sonic's death sprite from the Master System Sonic 1. The final version uses an updated sprite.
	Under Ground Zone Boss body	The entire body of the boss. Normally, only its head is visible. However, by extending the screen in the Game Gear release with an emulator, you can see it.
	Sky High Zone Boss body	The entire body of the boss. Normally, only its head and neck can be seen.

Monitors#

Artwork	Name	Description
	Sonic Monitor	While you can find this in a wall in Crystal Egg Zone, the graphics are obscured by foreground scenery making them difficult (but not impossible) to see. When collected, it grants a continue.
	Question Mark Monitor	May have given a random amount of rings or items, like in the 2-player mode of the Genesis version.
	Grey Sneaker Monitor	May have slowed you down, like the Speed-Down sneaker in the 2-player mode of Sonic 3.
	Arrow Monitor	Most likely intended to be a checkpoint marker, like the 8-bit versions of Sonic 1.

Level Art#

To do: Aqua Lake Zone, Green Hills Zone, Gimmick Mountain Zone, Scrambled Egg Zone all have many unused tiles, as do Sky High Zone Act 2 and Crystal Egg Zone Acts 1 and 2.

Artwork	Name	Description
	Under Ground Zone Bricks	Several unused bricks. Tiles similar to the gray bricks were used in the AutoDemo prototype.
	Under Ground Zone Tunnel	Leftovers from the curved tunnels found in the AutoDemo prototype.
	Under Ground Zone rock	A 32×32 rock that was used in the AutoDemo prototype.
	Under Ground Zone Tiles	Miscellaneous unused pieces.
	Under Ground Zone Floating Platform	An unused floating platform.
	Sky High Zone boulder	This boulder was probably supposed to roll down a hill in Act 1.
	Sky High Zone platform	Another unused floating platform.
	Sky High Zone object	Unknown purpose - another platform?
	Sky High Zone water	Water tiles that were supposed to appear in Act 2. They look similar to the tiles found in the AutoDemo prototype.
	Sky High Zone trees	The trees from Act 1 were apparently supposed to appear in Act 2, but they don't.
	Sky High Zone background	A 32×32 background tile that was supposed to appear in Act 2.
	Aqua Lake Zone block	A small additional piece of land. If placed in Act 2, these are fully functional and cause Sonic to slide down much like Labyrinth Zone in Sonic 1.
	Aqua Lake Zone waterfall	This waterfall tile was probably going to be used with the block above.
	Aqua Lake Zone spikes	Unused spikes that were supposed to appear in Act 1 and 3. The only spikes found in this Zone are underwater.
	Green Hills Zone grass	While the miscolored grass tile on the left is used in-game, an unused, properly-colored grass tile exists.
	Green Hills Zone tiles	Unused graphics for background scenery that look like a flower stem.
	Green Hills Zone spring	A diagonal spring in front of the scenery that isn't used anywhere.
	Gimmick Mountain Zone breakable block	A breakable 32×32 tile that isn't used anywhere in the level.
	Scrambled Egg Zone breakable block	A breakable 32×32 tile that looks very similar to the Gimmick Mountain one, still unused.
	Crystal Egg Zone background tiles	Mountain background tiles that aren't used anywhere. These mountains use the palette cycles that the spikes, rings and larger orbs use, and flash.
	Crystal Egg Zone tiles	Scenery tiles that aren't used anywhere. As with the mountains, the bottom of the tall orbs flash.
	Crystal Egg Zone flower	An unused flower. The flower center also flashes.

Screen Art#

Artwork	Name	Description
	Early Title Screen	Leftover Title Screen used in the AutoDemo prototype found at addresses 0x206A0 to 0x213AF.
	Title Card Numbers	Numbers in the same style as the title card letters, which go unused as the game instead uses Sonic 1-style numbers.

Gimmick Mountain Title Card#

Originally, the level card for Gimmick Mountain Zone used its full name. Due to lack of space on the screen, however, "Mountain" was shortened to "Mt."

Unused Palettes#

Both versions of the game contain several unused palettes, and interestingly, some of them appear to be leftovers from the AutoDemo prototype!

Test Palette#

A test palette composed of white, black, and various shades of gray.

It can be found at address 0x26E45 to 0x26E64 in the Game Gear version, and 0x2411F to 0x2412E in the Master System version.

Early Sega Screen#

Used on the AutoDemo's Sega screen.

It can be found at address 0x26E65 to 0x26E84 in the Game Gear version, and 0x2412F to 0x2413E in the Master System version.

Early Title Card#

This would be the palette that was originally used in the Title Card of the AutoDemo. However, it also ended up being used in the Level Select of the Master System version.

It can be found in the Game Gear version, at address 0x26E85 to 0x26EA4.

Sega Logo#

There is a palette for the Sega Logo to disappear.

It can be found just in the Game Gear version, at address 0x27005 to 0x27024.

Coming Soon Screen#

Used on the AutoDemo's "Coming Soon" screen.

It can be found at address 0x271C5 to 0x271E3 in the Game Gear version, and 0x242DF to 0x242EE in the Master System version.

Overwritten Colors#

Both versions contain palettes with different colors that get overwritten by palette cycles.

Intro#

The checkerboard colors are brown instead of gray, making them resemble the ones from Green Hill Zone in Sonic 1.

Sky High Zone Act 2#

The rain is dark blue instead of purple, and the lightning is white instead of light blue.

Gimmick Mt. Zone#

The cycling lights use a pink and a light yellow. Interestingly, an early screenshot appears to show the pink being used for scrapped rock graphics.

Scrambled Egg Zone#

The cycling lights use a couple red colors.

Crystal Egg Zone Acts 1 and 2#

The cycling orbs, rings, and spikes use a couple reddish-pink colors. Strangely, these levels use a duplicate pointer to Scrambled Egg Zone's palette cycle.

Crystal Egg Zone Act 3#

The cycling lights use a dark red color.

Unused Text#

A build date string can be found in the ROM at 0x000C0.

MS SONIC THE HEDGEHOG.2 Ver1.00 1992/09/05 SEGA /Aspect Co.,Ltd 

GG SONIC THE HEDGEHOG.2 Ver1.10 1992/09/12 SEGA /Aspect Co.,Ltd 

MS SONIC THE HEDGEHOG.2 Ver2.20 1992/12/09 SEGA /Aspect Co.,Ltd 

Unused Audio#

Music#

A peaceful, ethereal-sounding tune. What this song could have been used for is unknown, but it might have been an early theme for either Crystal Egg or Aqua Lake due to the similar style. The song also has some resemblance to the Present theme of Tidal Tempest in the Japanese/European soundtrack of Sonic CD. This song was removed from the Game Gear version, and was replaced by the sound effect that plays when Sonic (and Tails) look up at the stars at the end of the credits. Both of them use $92 as the song value.

Raw Music Pitches#

All tracks within both versions of the game are set to play at a semitone lower than they are actually programmed, though there are a few outliers by not just a semitones, but also an octave… or four. Please be aware that some of the internal keys set the pitch too high and may cause discomfort.

Sound Effects#

These were removed from the Game Gear version.

Hidden Signatures#

Present in both Sky High 1 and Green Hills 1 are the names TOM and END, either in the dirt or ring patterns. They refer to designer Tomozou Endo and anonymous level designer End respectively.

References#