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Proto:Sonic the Hedgehog 2 (Genesis)/Simon Wai Prototype

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This is a sub-page of Proto:Sonic the Hedgehog 2 (Genesis).

To do:
  • Replace the Beta 4 layout comparisons with August 21st comparisons.

Hiddenpalace.org logo.png  This prototype is documented on Hidden Palace.

Download.png Download Sonic the Hedgehog 2 (Simon Wai prototype)
File: Sonic The Hedgehog 2 (Simon Wai Prototype).bin (1 MB) (info)

The Simon Wai prototype of Sonic the Hedgehog 2 is definitely further along than the Nick Arcade build, but there are still quite a few unfinished elements such as level layouts and things that have not been fully implemented. There are also many, many unused graphics that can be found via hacking. In addition, there are a few levels not seen in the final, but most of them contain nothing.

According to drx, this prototype was built in early August 1992. The prototype is named after Simon Wai, who found it on a Chinese GeoCities page in 1998. However, it is believed to have first been leaked in September 1992 and distributed through BBS (bulletin board system) numbers. The origin of the actual ROM image is unknown. Magazines from the time attributed the leak to a specific magazine, while Yuji Naka stated in 2005 that it came from a demonstration cart that was stolen from a New York toy fair in 1992.

In any case, this build was one of the first video game prototypes to be dissected in detail. It kickstarted interest in prototypes for not only the Sonic fanbase, but the gaming community at large.


Sound Differences
It sounds more like the Masa's Demo versions than the actual game!

General Notes

  • The Sega logo does not appear when booting up the game. However, if you get a Game Over or clear the four Zones, the game does show the Sega logo and then shows the title screen. This also happens if you stay on the title screen and allow the resulting demo to run its course. The sound is also noticeably higher-pitched than in the final.
  • Uses the earlier title screen and lacks the title menu.
  • Any Zone with water will be glitched when playing in two-player mode, as the game loads the graphics incorrectly.
  • Special Stages are still not present, although the music is.
  • Debug Mode info is now properly white in every Zone.
  • The lower-right four digits now reserve the water level height (even in zones without water), while the lower-left four digits count up by one every in-game second.
  • Entering and exiting debug now automatically brings Tails to the player's location.
  • Locking on this prototype with Sonic & Knuckles will unlock the full Blue Sphere game, as it does with the Nick Arcade build. This is because the two prototypes have the same serial code as Sonic the Hedgehog (REV01), which determines the result of the lock-on.
  • Rolling demo gameplay is the same as the Nick Arcade build, and has not yet been rerecorded to fit subsequent layout changes.
  • The level select has the same general appearance as the level select from Sonic 1.
  • Special Stage cannot be selected on the level select, as they don't exist yet.
  • There are no checkpoints in the game. One can be placed via Debug Mode, where it can be seen that they have a totally different design to the one used in the final game.
  • The player starts most Acts positioned slightly more to the left than they do in the final game. However, this doesn't affect all levels.
Simon Wai - September 14, 1992 CENSOR onward
Sonic2 Sonic signpost Wai.png Sonic2 Sonic signpost Final.png
  • The shading on Sonic's signpost appears unfinished.

Level Select and Cheat Codes

Sonic2SimonWai-Alpha LevelSelect.png
  • Level Select - A + Start.
  • "Night Mode" - C + Start.
    • Unlike the final game, Debug Mode doesn't need to be active for this to work.
  • Two-Player Mode - on the level select, press B on any level that doesn't have water.
  • Debug Mode - C, C, Up, Down, Down, Down, Down, Up.
    • You can also enable it through the patch code FFFFFA:0001. The ring sound will play even if C is never pressed, but nothing else happens.
    • Layer switches are visible in this version's Debug Mode. A checkpoint sound is made whenever Sonic or Tails passes through them.
    • Tails jumps to Sonic's position when leaving Object Placement mode.


  • At this point, Tails is still quasi-independent:
    • Player 2 is able to control Tails, except Tails will also follow Sonic. The game doesn't lock P2's inputs, however it also doesn't stop Tails' AI.
    • Tails cannot complete a level on his own, since the game only loads the signpost when Sonic approaches it.
    • The AI is much simpler: it only follows Sonic and does not try to keep up.
    • Tails loses the player's rings when he is hit. This was also the case with the Nick Arcade build, in which Tails was disabled in that build's Emerald Hill, likely for the challenge from the Nick Arcade show.
    • If he dies, he drops back in from the top of the screen and immediately goes into a roll when he hits the ground because he can't fly yet.
  • If Player 1 completes a level, Tails can be controlled if Sonic is off-screen.
  • As with the Nick Arcade build, the Spin Dash is still a work-in-progress, as Sonic and Tails can only charge it up once; the sound for when Sonic spins in Sonic the Hedgehog is still heard due to there not yet being a specific sound effect for the Spin Dash.
  • As with the Nick Arcade build, the timer resets to 9:00 when it approaches 9:59 in order to allow the player to test the stages for extended periods of time.
  • The screen doesn't scroll up or down when you look up or down for a certain period of time.
  • Bubbles are loaded incorrectly from the VRAM.
  • A unique bug is present in this prototype: upon collecting 100 rings, the game will play the Death Egg Zone music instead of the usual 1-Up sound. This is because sound ID 88 (which was the 1-Up sound in the Nick Arcade build and also the Extra Life jingle in Sonic 1) has since been overwritten with the Death Egg music and not edited to play the correct sound. Game Genie code XCOT-AAC4 will cause the correct tune to play. The monitors, on the other hand, have been modified to use the new correct sound ID.
  • The underwater countdown music uses the Level Select theme for the same reason as the 1-up jingle. When Sonic gets out of the water, the Emerald Hill music begins.
  • Spike behavior is still the same as in Sonic 1 - getting hit does not give the player invincibility frames to avoid being immediately hurt from other spikes.
  • Rolling tubes do not force the player to roll, notably in Hill Top and Hidden Palace.
  • Speed Shoes do not increase the speed of the music.
  • No title cards or score tallies appear at the beginning and end of an Act respectively. However, the clear theme does play in the case of the latter.
  • The splashing animation is corrupted, showing misaligned bubbles instead of a splashing sprite. Tails has no splashing effects.
  • 2-Player mode has the split-screen for Sonic and Tails, but is otherwise identical to 1-Player mode. The level will still restart if Sonic dies.
  • Aquatic Ruin, Chemical Plant, Hill Top, and Emerald Hill are the only Zones where signposts appear. Animal Capsules do not exist yet.
  • Exclusively to this build, the game only ever loads Pocky (the rabbit) and Cucky (the chicken) in all zones; the remaining Sonic 1 critters are unused, while Sonic 2‍ '​s aren't in the ROM yet.


Without accessing the level select, the game allows you to play Aquatic Ruin, Chemical Plant, Hill Top, and Emerald Hill.

Internal Zone Order

Zones that are either placeholders or left over from a previous build are in italics, new levels are bold, and moved level slots are blue.

Sonic 1 Nick Arcade Proto Simon Wai Proto Final
00 Green Hill Green Hill Green Hill
(Emerald Hill)
Emerald Hill
01 Labyrinth Labyrinth leftovers
02 Marble Chemical Plant Wood Wood leftovers
03 Star Light Emerald Hill
04 Spring Yard Hidden Palace Metropolis Metropolis
05 Scrap Brain Hill Top Metropolis 3 Metropolis 3
06 Wing Fortress
07 Hill Top Hill Top
08 Hidden Palace Hidden Palace leftovers
0A Oil Ocean Oil Ocean
0B Dust Hill
(Mystic Cave)
Mystic Cave
0C Casino Night Casino Night
0D Chemical Plant Chemical Plant
0E Genocide City Death Egg
0F Neo Green Hill
(Aquatic Ruin)
Aquatic Ruin
10 Death Egg Sky Chase

This earlier Zone order seems to largely match the order seen in early concepts for the game which involved time travel. Based on the timeline, Zone 01 would be Ocean Wind, Zone 03 would be Sand Shower, Zone 06 would be Blue Lake/Blue Ocean, and Zone 09 would be Rock World. However, there are some deviations from those concepts even at this point in development: it appears that Zone 05 was likely going to be Tropical Plant/Tropical Sun, and it's Metropolis 3 both here and in the final. Additionally, Neo Green Hill doesn't appear in any of those timezone maps. Most curiously, Mystic Cave is also unmentioned in those concepts, and is called Dust Hill here; the latter name is mentioned in the early timeline and assigned to what seems to be a crumbling Green Hill.

For most Zones out of the "normal" game loop (Neo Green Hill -> Chemical Plant -> Hill Top -> Green Hill), placing object 3A in the final Act will make the game jump to the next Zone by ID. For ID 01, ID 03, ID 06, ID 09, and Death Egg, the game will jump to Green Hill.


Green Hill Zone
Behold the monkeyfication!
Metropolis Zone
Vertical wrapping!
Hill Top Zone
Lava hurts now!
Oil Ocean Zone
Too many checkered balls!
Dust Hill Zone
A pretty empty cavern!
Casino Night Zone
Pink and blue nightmare!
Chemical Plant Zone
The same, but different!
Neo Green Hill Zone
Semi-aquatic ruins!

Zone ID 01

Sonic2gen waiproto GHZRemains.PNG
  • Uses Emerald Hill's palette and music. Debug mode only has the default Ring and Static Monitor objects.

This empty stage slot can be accessed by entering Game Genie code AA7A-ACGY or Pro Action Replay code FFFE10:0100 and choosing Green Hill Zone Stage 0 in the level select. Sonic and Tails immediately fall to their deaths upon entering.

Wood Zone (ID 02)

Does this level look flat to you?

A scrapped Zone. It seems that only a small portion was ever implemented and did not get too far.

  • What exists of the level quickly ends because of a ramp that has a solid platform blocking the top of it, which is impossible to get past without Debug Mode. Even then, the rest of the level is incomplete, with a nonfunctional conveyor belt near the top.
  • Plays the music for Metropolis Zone.
  • If you use Debug Mode, you can move upwards in the level and find a conveyor belt, but it doesn't work.
  • Level collision is glitchy.
  • Unlike any other Zone in the game, the entire background is located under the stage instead of in the background layer.
  • Act 2 is empty, containing nothing but Sonic and Tails falling to their deaths.
Sonic2WaiProto MapWZ.png

Zone ID 03

Sonic2gen waiproto Zone03Leftovers.PNG
  • Uses Emerald Hill's palette, the final Oil Ocean theme, and only has the default Ring and Static monitor objects in debug mode.

This empty stage slot can be accessed by entering Game Genie code AA7A-AGGY or Pro Action Replay code FFFE10:0300 and choosing "Green Hill Zone Stage 0" on the level select. This stage is entirely empty, causing Sonic and Tails to immediately fall to their deaths upon entering. In the Nick Arcade prototype, this slot was used for Emerald Hill Zone.

Zone ID 06

Sonic2gen waiproto WFZSlot.PNG

This is an empty stage slot that can be accessed by entering the Game Genie code AA7A-ANGY or Pro Action Replay code FFFE10:0600 and choosing "Green Hill Stage 0" on the level select. As with the others, the stage is entirely empty, prompting Sonic and Tails to fall to their immediate deaths upon entering.

From the September 14th build onwards, the stage is used for Wing Fortress Zone.

  • Contains a pitch-black background, uses what would become the two-player Emerald Hill theme in the final.
  • For some reason, this zone uses a copy of Casino Night's palette that is specifically loaded in Casino Night Act 2.

Hidden Palace Zone (ID 08)

It took them 21 years, but they finally finished it.

Has very few changes from the previous version. For more info, see the Nick Arcade prototype page.

  • This Zone has had mainly minor behind-the-scenes changes since the Nick Arcade build.
  • Sonic and Tails have had their underwater palette updated.
  • The music has been changed to what would be the 2P VS version of Mystic Cave in the final.
  • The debug list has had a face lift, and all the unused objects that were in the Nick Arcade build are now gone. The items that are still there have fixed previews.
  • The collision bug caused by spindashing into the big emerald from far away has been fixed.
  • The art for Emerald Hill's enemies are no longer loaded in this Zone.
  • This and Emerald Hill are the only Zones in this build with badniks in them.
Sonic2WaiProto MapHPZ.png

Zone ID 09

Sonic2gen waiproto SCZSlot.PNG
  • Uses Emerald Hill's palette, Sky Chase's music, and only has the default Ring and Static monitor objects in debug mode.

By entering Game Genie code AA7A-AWGY or Pro Action Replay code FFFE10:0900 and choosing "Green Hill Stage 0" on the level select, the player will be taken to yet another empty Zone that promptly causes Sonic and Tails to fall to their deaths.

Genocide City Zone (ID 0E)

What are you?
  • Both Acts use Chemical Plant's music, Emerald Hill's palette, and the default Ring and Static Monitor objects in debug mode. They're also completely empty.

It is called "Genocide City" in this build because of an average understanding of English by the person who originally named it, then changed to Cyber City after this prototype. Before the team started putting it in the game, though, it was scrapped and the graphics were later used in Level 3 of Sonic Spinball (The Machine).

The level slot for this level was overwritten with Death Egg in the final, while the slot for Death Egg in this prototype (ID 10) was overwritten with Sky Chase.

Death Egg Zone (ID 10)

  • Uses Emerald Hill's palette, but has no music and is empty. Dying here causes all sound to cut off. However, if you use the 100 ring glitch via debug mode and then die, it will not cut off for that particular death.

Unused Graphics and Objects

Most of the changed and unused graphics and objects in the Nick Arcade prototype are still here, with the following exceptions:

  • The signposts and fireballs use their final graphics.
  • The early animated Chemical Plant graphics are no longer in the ROM.
  • The JIS X 0201 character set has been deleted.
  • Hill Top's one-way barrier and the nebulous gray switch have been coded and placed in various Zones.
  • Chemical Plant's floating platforms now behave as they do in the final game.


Graphic Offset Compression Description
0x28A6A None Animated drill tiles for use in Metropolis Zone. These are loaded to slots 368-377 in VRAM, though the game mistakenly loads two copies of the horizontal drill instead of the vertical drill; according to concept art, the horizontal screw were meant to be used under the flat moving platforms in the stage, and lining the horizontal screws with the platforms show they match up perfectly. Where the vertical screw was meant to be used is anyone's guess.
0x77472 Nemesis This is the vine that acts as a switch in Mystic Cave Zone. It has not yet been coded at this point.
0x7756A Nemesis The hanging vine from Mystic Cave Zone. It hasn't been coded, either.
Sonic2 waiproto-ChikiChikiBoysLeftover1.gif
0x4E8A6 None These graphics are leftovers from Chiki Chiki Boys. This probably resulted from the process of compiling and burning ROMs onto EPROM chips.
Sonic2 waiproto-ChikiChikiBoysLeftover2.gif
0x4B76C None
(Source: Sonic Retro)


Object ID Graphic Name Description
Monitor subtype Breaking this monitor will load Super Sonic's palette.
When you order the Chaos Emeralds on Wish:

The same effect can be seen through Pro Action Replay code FFF65F:FF00. Super Sonic's unique sprites, speed, invincibility, jump height, and ring drain are not yet present.

(General information: Sonic Retro)

Unused Sound Effects

This prototype also has several sound effects that cannot be heard in normal gameplay. Many of these are early versions of sound effects in the final game. These can be heard via the sound test.

Sound ID Simon Wai Audio Final Audio Notes
Egg Claw's electricity conductor
Unused (2P mode time alarm, low pitched)
2P mode alarm
OOZ popping platform
OOZ sliding spike colliding
CNZ elevator
MCZ swinging platforms hitting each other
CNZ disappearing objects being bounced on
CNZ large horizontal bumper
CPZ poisonous bubble chain
Mecha Sonic lowering/Death Egg Robot launching
Egg Hammer's arrow hitting the pole
Egg Drillster/Wing Fortress propellers
Transforming into Super Sonic
Early version of the Spin Dash sound. It doesn't rise in pitch each time it's played.

Unused Auto Demo

There's partial data for a Metropolis Zone Act 3 in the demo table that can be viewed using patch code FFFFF2:0004.

This is actually caused by the demo table not being converted after the Nick Arcade prototype:

Zone ID 02 03 04 05 05 05 05 05 04 04 04 04

02 is Chemical Plant, 03 is Green Hill, 04 is Hidden Palace, and 05 is Hill Top. The first four entries are valid, while the remaining entries are placeholders.

In the Simon Wai prototype, the table was changed:

Zone ID 0D 00 08 07 05 05 05 05 04 04 04 04

Chemical Plant, Green Hill, Hidden Palace, and Hill Top use their new level IDs, but the duplicate Hidden Palace and Hill Top entries were not converted. They now point to Metropolis Act 1/2 and Metropolis Act 3 respectively.

The Metropolis Zone demo uses the input from the 2P Green Hill demo, which doesn't really work out.

Unassembled Data

Located at address 0xE5946 is a snippet of unassembled data. It starts with the comment at the top

; 圧縮前 $8000  圧縮後 $2c00  圧縮率 34.4%  セル数 1024

...which translates to:

; Before compression $8000  After compression $2c00  Compression ratio 34.4%  Number of cells 1024

What follows is a bunch of "dc.b"s for the actual chunk data. When assembled, its data matches the beginning of Neo Green Hill Zone's chunk data located at 0xBF568. While a good chunk of the unassembled data is there, it gets cut off.

	dc.b	$1d,$7f,$00,$ff,$f8,$7e,$04,$01,$fb,$02,$00,$03,$04,$05,$04,$80
	dc.b	$ff,$fa,$ff,$07,$54,$0b,$54,$0a,$50,$0c,$50,$ff,$8f,$0d,$54,$0f
	dc.b	$54,$0e,$50,$10,$50,$11,$52,$19,$52,$18,$ff,$ff,$fc,$1a,$52,$1b
	dc.b	$51,$8a,$51,$8b,$52,$1c,$02,$1e,$02,$1f,$02,$2a,$9f,$ff,$02,$2b
	dc.b	$01,$8c,$01,$8d,$f4,$1d,$02,$2c,$02,$2d,$01,$ff,$f4,$88,$01,$89
	dc.b	$01,$8e,$01,$8f,$02,$1a,$e4,$02,$2e,$02,$46,$c0,$2f,$e0,$ff,$1b
	dc.b	$ec,$fc,$dc,$00,$70,$02,$c4,$d4,$ee,$18,$02,$19,$01,$3f,$f6,$fd
	dc.b	$e4,$e6,$04,$2e,$04,$2d,$04,$9d,$fe,$77,$bd,$00,$be,$f9,$50,$31
	dc.b	$54,$30,$54,$2f,$7f,$f8,$56,$03,$56,$02,$56,$01,$05,$ff,$f0,$52
	dc.b	$1d,$52,$1e,$e1,$9f,$52,$1f,$fc,$50,$3e,$54,$3c,$56,$04,$54,$36
	dc.b	$09,$e0,$c4,$9c,$f8,$ea,$1a,$50,$48,$24,$41,$ba,$a4,$b2,$fc,$fc
	dc.b	$21,$9a,$f2,$80,$f6,$9c,$fc,$1d,$5e,$92,$68,$01,$8a,$01,$8b,$ee
	dc.b	$fc,$68,$f2,$fd,$d5,$fd,$ce,$f7,$f7,$80,$fd,$f0,$f8,$0f,$04,$35
	dc.b	$f0,$f8,$0d,$54,$3f,$54,$39,$7f,$fe,$54,$38,$01,$ff,$02,$00,$06
	dc.b	$00,$60,$1a,$54,$43,$54,$ff,$f3,$42,$55,$fe,$55,$fd,$55,$fc,$55
	dc.b	$fb,$54,$46,$a4,$1c,$ff,$11,$50,$49,$54,$44,$54,$52,$50,$51,$54
	dc.b	$50,$80,$b2,$12,$8e,$8f,$4e,$06,$fc,$f2,$f2,$3c,$90,$fa,$58,$5c
	dc.b	$80,$f8,$20,$60,$f8,$20,$40,$f3,$02,$0a,$02,$2c,$3c,$0b,$70,$40
	dc.b	$f6,$86,$2a,$54,$29,$52,$f4,$62,$f8,$11,$c0,$f1,$2a,$52,$2b,$bc
	dc.b	$f4,$fc,$1a,$62,$f1,$72,$6e,$f2,$f2,$78,$00,$16,$bd,$fe,$00,$17
	dc.b	$fc,$f8,$0c,$18,$00,$19,$fc,$f8,$0c,$e0,$f8,$2e,$54,$06,$54,$04
	dc.b	$50,$fb,$be,$08,$50,$09,$f8,$fe,$50,$12,$50,$13,$fc,$f8,$0b,$00
	dc.b	$14,$00,$15,$f7,$fc,$fc,$f8,$0c,$1e,$00,$1f,$fc,$f8,$0c,$20,$00
	dc.b	$21,$fc,$f4,$50,$f5,$f7,$07,$50,$f6,$50,$f7,$e8,$fe,$50,$f8,$50
	dc.b	$87,$52,$1b,$3c,$1f,$fd,$e0,$fc,$50,$f9,$50,$85,$40,$ae,$f1,$50
	dc.b	$fa,$50,$fb,$07,$e1,$50,$fc,$50,$8b,$f6,$86,$f1,$2a,$1c,$50,$2f
	dc.b	$b2,$8c,$50,$8d,$50,$8e,$24,$f1,$24,$ee,$0a,$24,$9a,$eb,$92,$f3
	dc.b	$7c,$f2,$0a,$f2,$e0,$ec,$af,$9f,$dc,$05,$6d,$ae,$ef,$60,$f2,$1a
	dc.b	$06,$25,$01,$89,$45,$94,$e4,$4e,$ed,$e0,$e8,$2a,$f3,$11,$ae,$e0
	dc.b	$f0,$c0,$28,$02,$29,$38,$f6,$00,$8c,$c0,$fd,$ce,$e4,$a0,$59,$44
	dc.b	$c0,$8d,$ce,$00,$ea,$bc,$e0,$0b,$a8,$d6,$fc,$1b,$dc,$e2,$f8,$f0
	dc.b	$68,$ec,$ea,$bd,$f8,$e5,$20,$f0,$15,$a0,$e8,$09,$20,$f0,$16,$50
	dc.b	$54,$0d,$20,$f5,$1b,$52,$1c,$92,$a0,$dc,$e4,$60,$e5,$a8,$6e,$e2
	dc.b	$80,$6e,$e4,$82,$28,$12,$fc,$4e,$e2,$80,$6e,$e2,$44,$ee,$e7,$fa
	dc.b	$00,$66,$8e,$fe,$56,$25,$51,$8c,$c0,$c2,$e4,$bc,$f0,$fe,$38,$02
	dc.b	$15,$d8,$80,$fc,$06,$f8,$9d,$59,$f0,$12,$02,$11,$02,$10,$80,$fc
	dc.b	$f6,$5a,$30,$fe,$e0,$ee,$13,$80,$2e,$52,$2f,$f9,$6d,$7f,$f5,$05
	dc.b	$f9,$02,$16,$00,$23,$00,$24,$e4,$f3,$f2,$f1,$80,$ea,$50,$2b,$20
	dc.b	$8c,$50,$76,$5a,$f3,$84,$51,$89,$40,$a0,$5c,$58,$60,$6e,$00,$f9
	dc.b	$11,$95,$ae,$f5,$1b,$5a,$f6,$6a,$e3,$6a,$fc,$02,$82,$e8,$10,$96
	dc.b	$ee,$ea,$47,$0f,$ce,$f2,$13,$02,$14,$76,$b2,$f2,$16,$02,$17,$44
	dc.b	$8c,$ee,$e4,$88,$ea,$33,$fa,$d4,$04,$23,$f2,$e4,$e6,$fc,$54,$27
	dc.b	$54,$4f,$e4,$94,$54,$93,$04,$92,$e0,$ea,$e4,$f2,$54,$af,$af,$85
	dc.b	$54,$97,$04,$98,$c6,$fd,$52,$f3,$54,$87,$54,$99,$bc,$fc,$ff,$ff
	dc.b	$00,$e8,$39,$50,$6b,$50,$6c,$50,$6d,$50,$73,$50,$74,$50,$75,$50
	dc.b	$76,$50,$ff,$8f,$77,$50,$78,$50,$79,$50,$15,$50,$7a,$50,$7b,$50
	dc.b	$7c,$5e,$51,$f8,$20,$ee,$12,$00,$13,$fc,$f8,$0c,$00,$e8,$0e,$08
	dc.b	$6e,$e2,$4d,$d2,$fc,$f2,$bc,$d2,$8a,$32,$ee,$f6,$60,$04,$f0,$fa
	dc.b	$22,$fa,$00,$23,$06,$5c,$32,$fc,$80,$f1,$26,$54,$25,$67,$c1,$50
	dc.b	$27,$f6,$58,$20,$80,$f2,$20,$60,$d1,$51,$55,$f1,$6d,$d8,$80,$f3
	dc.b	$cc,$f3,$28,$f1,$80,$f0,$09,$12,$dc,$2d,$a3,$04,$e1,$d8,$ea,$18
	dc.b	$84,$d6,$a0,$d8,$4f,$41,$80,$f4,$02,$25,$01,$24,$ae,$05,$c0,$80
	dc.b	$f4,$88,$23,$f0,$25,$92,$12,$05,$fa,$ab,$02,$d6,$e0,$ff,$92,$f3
	dc.b	$e0,$fc,$8a,$f1,$e0,$86,$a7,$88,$10,$88,$01,$f9,$01,$fa,$80,$5d
	dc.b	$21,$05,$fa,$60,$fc,$50,$28,$80,$fe,$e0,$e9,$fc,$2d,$1b,$94,$84
	dc.b	$bc,$c9,$52,$86,$c0,$ce,$64,$ea,$2a,$7c,$74,$19,$fa,$e9,$76,$d2
	dc.b	$58,$55,$05,$48,$01,$5d,$f9,$5e,$f2,$fc,$f4,$57,$05,$52,$85,$e9
	dc.b	$1b,$05,$49,$f4,$fe,$02,$d5,$ff,$f2,$f4,$f8,$09,$ff,$f8,$32,$32
	dc.b	$d6,$96,$ca,$ff,$d8,$38,$50,$39,$50,$3f,$a2,$49,$a2,$4a,$fc,$54
	dc.b	$ea,$fe,$7f,$af,$02,$0d,$02,$0e,$02,$0f,$06,$0d,$cc,$f8,$0a,$c1
	dc.b	$00,$c2,$bc,$f8,$0c,$d2,$f9,$f0,$f8,$2c,$c0,$e1,$f0,$07,$04,$05
	dc.b	$f1,$07,$51,$bf,$aa,$75,$50,$c1,$50,$c2,$54,$31,$a0,$c6,$ac,$da
	dc.b	$ee,$f5,$46,$f2,$aa,$20,$60,$f3,$e4,$f3,$dc,$de,$d2,$cc,$6e,$de
	dc.b	$d4,$52,$d8,$0c,$b2,$ac,$e2,$e8,$5c,$f3,$d8,$c8,$e2,$82,$b2,$20
	dc.b	$de,$34,$f3,$ec,$1a,$f2,$84,$db,$b8,$84,$6a,$e8,$fe,$c4,$b8,$c0
	dc.b	$b8,$49,$20,$fc,$c0,$b8,$10,$1b,$2d,$e8,$08,$f3,$00,$f1,$51,$fc
	dc.b	$da,$8a,$f2,$bd,$ae,$d7,$97,$01,$73,$06,$99,$fc,$fe,$98,$f6,$e4
	dc.b	$04,$0a,$fc,$f6,$f4,$9b,$7f,$46,$f6,$06,$9f,$02,$e2,$0a,$98,$0a
	dc.b	$f4,$e6,$38,$e9,$fe,$e3,$04,$00,$fa,$f4,$fc,$50,$f5,$93,$43,$e2
	dc.b	$06,$91,$02,$fe,$92,$f8,$f0,$07,$84,$98,$06,$96,$02,$fe,$b0,$f8
	dc.b	$91,$20,$06,$95,$f0,$c4,$fe,$9a,$8d,$87,$f8,$06,$9c,$f0,$e4,$02
	dc.b	$e5,$aa,$08,$fe,$02,$bc,$f8,$fa,$eb,$32,$50,$33,$50,$34,$9f,$ff
	dc.b	$50,$b4,$50,$b5,$50,$b6,$fc,$b7,$50,$b8,$50,$b9,$54,$e1,$fb,$b9
	dc.b	$f0,$fe,$ba,$f0,$bb,$f0,$bc,$68,$d2,$06,$19,$fc,$ff,$f4,$ae,$fc
	dc.b	$ad,$fc,$ac,$fc,$ab,$fc,$aa,$f0,$fc,$a6,$fc,$fb,$8b,$a5,$fc,$a4
	dc.b	$48,$d6,$30,$be,$3c,$a3,$3c,$a2,$38,$d0,$09,$c5,$56,$f0,$a1,$58
	dc.b	$c0,$0b,$f0,$a0,$f0,$f8,$0e,$9f,$40,$b0,$52,$58,$d5,$b5,$6e,$80
	dc.b	$f7,$58,$d5,$80,$f0,$0d,$f1,$72,$cc,$80,$f7,$01,$6d,$c0,$f8,$1e
	dc.b	$58,$45,$fd,$48,$f6,$bc,$fc,$c0,$c0,$ee,$9c,$ea,$18,$a1,$6d,$01
	dc.b	$4b,$f8,$48,$05,$55,$8e,$cc,$a6,$f0,$52,$05,$57,$d1,$a0,$05,$56
	dc.b	$ec,$38,$ea,$88,$a0,$32,$cb,$c0,$fe,$ec,$fe,$c6,$f0,$ec,$fe,$01
	dc.b	$1f,$02,$5d,$01,$ff,$bf,$0f,$01,$10,$02,$45,$02,$30,$02,$31,$c1
	dc.b	$da,$c2,$33,$c2,$32,$ff,$cf,$d2,$e2,$02,$34,$02,$35,$02,$32,$c1
	dc.b	$db,$c2,$3c,$02,$3d,$7f,$00,$f0,$47,$02,$36,$02,$37,$c1,$dc,$e0
	dc.b	$ea,$0e,$ff,$f0,$44,$ce,$c5,$d8,$c1,$d9,$02,$40,$02,$f0,$ff,$41
	dc.b	$f0,$c1,$d4,$c1,$d5,$c1,$d6,$c1,$d7,$02,$3e,$02,$ff,$3f,$3f,$02
	dc.b	$46,$c0,$c1,$c0,$c2,$c2,$3a,$c2,$3b,$02,$38,$02,$39,$01,$02,$d8
	dc.b	$f0,$d0,$c8,$02,$7e,$c0,$c4,$f8,$30,$01,$29,$01,$2a,$02,$44,$92
	dc.b	$d6,$aa,$c0,$a3,$aa,$80,$d3,$8b,$2e,$ca,$d3,$a0,$c9,$9a,$d2,$a4
	dc.b	$cd,$aa,$eb,$80,$cf,$a4,$cd,$66,$d2,$a8,$ce,$80,$d6,$04,$5e,$72
	dc.b	$ce,$60,$d5,$5d,$97,$f6,$54,$61,$54,$60,$e4,$fc,$ea,$52,$1c,$e0
	dc.b	$a9,$63,$54,$ff,$da,$62,$54,$67,$54,$66,$54,$65,$54,$64,$f2,$bc
	dc.b	$e0,$ac,$54,$e0,$a9,$7f,$e1,$51,$fb,$51,$fc,$51,$fd,$51,$fe,$80
	dc.b	$e8,$0f,$fc,$50,$ba,$5b,$50,$50,$bb,$50,$80,$e8,$14,$0c,$80,$e8
	dc.b	$0c,$f0,$80,$e8,$7b,$e0,$d8,$3f,$fd,$ef,$ec,$e9,$9a,$f2,$1e,$54
	dc.b	$9d,$54,$9c,$54,$90,$54,$8f,$92,$b7,$1c,$1f,$d5,$54,$8e,$54,$8d
	dc.b	$50,$50,$e0,$e8,$ba,$b2,$9e,$80,$9a,$aa,$aa,$1d,$9c,$bb,$c4,$da
	dc.b	$7c,$ea,$ba,$b2,$36,$db,$f8,$9d,$00,$be,$aa,$f4,$a0,$c8,$09,$8e
	dc.b	$a6,$0e,$a3,$92,$c6,$c0,$9a,$d4,$04,$24,$00,$c2,$ff,$5a,$32,$f0
	dc.b	$09,$e6,$54,$4f,$54,$4e,$54,$4d,$54,$4c,$54,$d5,$7e,$59,$54,$9c
	dc.b	$c3,$a8,$b1,$00,$ea,$1c,$80,$99,$57,$54,$56,$54,$5f,$11,$55,$60
	dc.b	$ff,$aa,$ea,$80,$9a,$a0,$fe,$06,$bc,$95,$54,$68,$d6,$5c,$d6,$12
	dc.b	$9c,$56,$dc,$e4,$9a,$ea,$84,$c4,$8f,$3f,$5c,$ac,$51,$09,$83,$f2
	dc.b	$62,$02,$63,$01,$88,$05,$7c,$a2,$f6,$51,$00,$91,$09,$24,$f2,$fc
	dc.b	$10,$25,$05,$64,$91,$f0,$96,$b2,$ee,$61,$1d,$92,$c1,$f2,$50,$91
	dc.b	$a8,$c2,$fc,$fe,$f0,$96,$ac,$b0,$f0,$48,$b1,$8d,$64,$e1,$20,$c3
	dc.b	$f0,$00,$9e,$8c,$aa,$92,$95,$78,$f2,$60,$f8,$09,$8e,$93,$92,$f3
	dc.b	$d1,$f5,$72,$90,$09,$1f,$36,$44,$ef,$00,$53,$40,$b1,$fa,$f1,$50
	dc.b	$4a,$ff,$ff,$50,$4b,$50,$4c,$50,$4d,$50,$4e,$50,$4f,$50,$55,$50
	dc.b	$56,$50,$57,$3d,$48,$50,$3d,$f8,$f5,$18,$50,$40,$f6,$fc,$f7,$2a
	dc.b	$a9,$2a,$20,$9a,$b6,$bb,$20,$90,$0a,$e8,$ee,$fe,$e8,$a4,$a4,$ff
	dc.b	$e4,$f4,$c6,$80,$de,$0e,$b5,$50,$46,$50,$47,$50,$48,$50,$3f,$c2
	dc.b	$3a,$50,$3b,$50,$42,$50,$43,$a0,$ff,$51,$5f,$55,$50,$52,$50,$44
	dc.b	$50,$45,$d8,$f1,$3c,$f2,$e4,$c3,$2e,$f8,$09,$a0,$8e,$95,$05,$a0
	dc.b	$fd,$80,$88,$0a,$e0,$ef,$0e,$b2,$c5,$ce,$55,$62,$00,$bb,$5c,$f8
	dc.b	$0a,$60,$f6,$5c,$8a,$3c,$5a,$2b,$2a,$d2,$fe,$01,$12,$a0,$09,$52
	dc.b	$f3,$f0,$5a,$f3,$8e,$fe,$30,$91,$f0,$b6,$f2,$ea,$8a,$32,$c0,$d1
	dc.b	$96,$fd,$2e,$bd,$f0,$b2,$fe,$12,$cb,$2c,$c0,$40,$fd,$0e,$a0,$5c
	dc.b	$8f,$be,$56,$a0,$a6,$4e,$a2,$51,$82,$b8,$09,$88,$a1,$53,$22,$b8
	dc.b	$2d,$c0,$82,$f5,$27,$f0,$f8,$0b,$a6,$b9,$c0,$81,$54,$34,$54,$33
	dc.b	$54,$32,$f0,$ed,$92,$40,$d1,$e0,$ea,$1a,$c0,$82,$54,$37,$c0,$81
	dc.b	$68,$68,$55,$72,$f2,$58,$aa,$81,$41,$00,$e0,$60,$8e,$b0,$0a,$c0
	dc.b	$80,$09,$7a,$b0,$0a,$bf,$28,$80,$c0,$40,$c0,$be,$cc,$a3,$cc,$00
	dc.b	$d8,$0a,$f0,$00,$d8,$0c,$8a,$ba,$f0,$00,$d8,$0c,$f0,$00,$d8,$0a
	dc.b	$88,$fe,$54,$b4,$7f,$fd,$cc,$f4,$f4,$bc,$f4,$bb,$f4,$ba,$f4,$80
	dc.b	$d1,$7c,$d1,$bf,$50,$c0,$f8,$ff,$fa,$aa,$f8,$ab,$f8,$ac,$f8,$ad
	dc.b	$f8,$ae,$d4,$91,$26,$b7,$f8,$b1,$f8,$fb,$dd,$b2,$f8,$b3,$16,$b0
	dc.b	$0b,$38,$af,$38,$b0,$30,$06,$b0,$0c,$38,$a9,$f0,$f8,$0e,$d6,$ed
	dc.b	$a8,$f0,$f8,$0e,$a7,$f0,$f8,$0d,$ff,$f8,$13,$f0,$d5,$f0,$f8,$0e
	dc.b	$d6,$f0,$f8,$0e,$d7,$fd,$ff,$05,$6e,$f2,$f8,$09,$f4,$d8,$f0,$d9
	dc.b	$55,$71,$55,$70,$55,$6f,$50,$dd,$7f,$7f,$f0,$de,$f0,$df,$f0,$e0
	dc.b	$f2,$18,$00,$f1,$72,$51,$73,$50,$ef,$f0,$d8,$f0,$ff,$f1,$f2,$00
	dc.b	$d9,$a2,$fe,$1f,$a1,$88,$7f,$70,$a1,$89,$a2,$2c,$a2,$2d,$a2,$1a
	dc.b	$f4,$f8,$c8,$67,$02,$59,$5d,$ef,$a0,$6c,$f0,$fe,$f2,$5a,$00,$d4
	dc.b	$9b,$f8,$4c,$2d,$00,$2e,$ac,$e8,$0a,$2f,$ff,$6d,$50,$30,$50,$31
	dc.b	$50,$36,$50,$37,$50,$3c,$40,$df,$1e,$40,$d9,$1b,$ad,$6a,$7c,$e7
	dc.b	$54,$e2,$8d,$88,$94,$f8,$d4,$a0,$8c,$92,$8e,$ee,$cb,$8f,$05,$19
	dc.b	$ee,$bf,$2a,$e2,$f4,$80,$88,$0a,$e6,$04,$14,$f2,$e0,$ba,$f6,$ee
	dc.b	$c0,$d3,$94,$f5,$e0,$c0,$d0,$15,$58,$85,$80,$84,$da,$

This data also appears in the ROM of August prototype, also being present in the same location, funnily enough.

Early Zone Leftovers

To do:
There's still more leftover bits throughout the ROM that have not been documented.

Starting at 0xC2148 in the ROM is leftover Zone data from an earlier point in development; the build the data comes from likely post-dates the Summer 1992 screenshots, as Chemical Plant's blue pipes have reached their final design by this point.

Early Casino Night Chunks

Located at 0xC2148-0xC943C is what looks to be chunk data for a very early version of Casino Night Zone, used as padding. Compared to the used data in the prototype, they are uncompressed, and partially cut off, leaving the archive to start at what would correspond to chunk 0x1E in the prototype normally. Almost none of the data works with the normally used, corresponding art and block mappings for Casino Night, implying the tileset used would have looked very different.

Early Chemical Plant Remnants

Starting at offset 0xC943C is data for an early version of Chemical Plant, which includes tiles, block and chunk data. They are much different from the used data, and when formatted correctly, line up much more with the layout from the Nick Arcade prototype, although blue pipes already have their finalized design, as do gray pipes, and one of the chunks (the top of a speed booster) now is a random pipe chunk.

Nick Arcade Simon Wai Leftovers Simon Wai
Sonic2NA CPZ128.png Sonic2WaiLeftovers CPZ128.png Sonic2Wai CPZ128.png

Early Neo Green Hill Remnants

Starting at 0xD602E is a bunch of early data related to Neo Green Hill Zone, including chunks, blocks, and two sets of tiles that are identical to those used, with one set being cut off by some chunk data; compared to this build, the following two chunks were changed:

Earlier Build Simon Wai
Sonic2Early NGHZChunk62.png Sonic2SimonWai NGHZChunk62.png
Earlier Build Simon Wai
Sonic2Early NGHZChunkC9.png Sonic2SimonWai NGHZChunkC9.png

Also located at 0x42374-0x4265F is an unused BG layout that is similar to the Act 2 layout used in the final game. Overall, the Zone appears to have not changed much between these two versions.

Chiki Chiki Boys Data Leftovers

The cartridge used to hold this prototype once contained a ROM of Chiki Chiki Boys, various leftovers from which exist in various parts of the ROM (though here they're little more than padding). The locations of the data in the Sonic 2 ROM match the equivalent area in both versions of the Chiki Chiki Boys ROM, but with some slight differences suggesting that the remnants here may be from a prototype.

Miscellaneous data can be found at:

  • 0x24A30-0x27FFF
  • 0x437BC-0x43FFF
  • 0x46350-0x47FFF
  • 0x48DB4-0x4FFFF