Sonic Chaos (Game Gear)

Sonic Chaos brings back Tails, this time as a playable character. Chaotic!

This is a port of the Master System version.

Sub-Pages#

Prototype Info Changes from the Master System VersionWho removed the rings in the boss fights again?!

Unused Graphics#

Artwork	Zone	Description
	Title Screen Ring	Graphics for the title screen's large spinning ring which are loaded on the title screen. This may have been used for a title screen animation. Interestingly, they are not present in the Japanese version.
	Turquoise Hill Zone	A diagonal spring likely intended for the lower parts of the stage.
	Gigapolis Zone	One default spring and four springs in front of some background blocks. There are also spikes meant to be placed in front of background blocks.
	Gigapolis Zone	A left-facing quarter pipe.
	Sleeping Egg Zone	A diagonal spring in front of the checkerboard background tiles, and some default spike graphics.
	Sleeping Egg Zone	Two different slope types that are unused in this Zone.
	Mecha Green Hill Zone	Diagonal springs and spikes set in front of the mesh background tiles.
	Mecha Green Hill Zone	A small unused level piece. A mirrored version of this is used.
	Aqua Planet Zone	Two different spring types, and two background objects.
	Electric Egg Zone	Another quarter pipe and spring type.
	Special Zone (Type #1)	A great number of background pieces intended to be placed with the diagonal background tiles. So are the spikes, which may have had their colors overwritten with the cloud palette.
	Special Zone (Type #1)	Two more quarter pipe blocks.
	Special Zone (Type #2)	The second Special Zone tileset has the most unused tiles of any level. This includes the giant rings featured in the other Special Zones, purple and red coral, spikes, and an upward spring. The red blocks are never used in any Special Stage. The presence of these blocks suggests that at one point in development the red Chaos Emerald may have had its own Special Stage.
	Special Zone (Type #2)	Both of the Special Zones using this tileset are completely flat. Nevertheless, these slope and quarter pipe tiles are present in the ROM.

Unused Zones#

Watch on YouTube

This needs some investigation. Discuss ideas and findings on the talk page. Specifically: What happens when you try to load these zone values into the various prototypes of the game on both versions.

Existing in both versions of the game, Zone IDs $06 and $0D have a blank name. In the Game Gear version, they show up as garbled text followed by "ZONE". In the Master System version, they just show up as "ZONE". Both levels function normally with the exception of the boss, which causes camera and VRAM issues.

Layout-wise, they're a copy of Turquoise Hill with few differences, apart from the occasional graphical glitch:

• The giant Motobug boss in Act 3 is glitched: after it is attacked once, it stays in its "flashing" palette for the rest of the fight.
• The HUD doesn't clear correctly before the boss, and continuously loops around the screen until part of it becomes overwritten by the boss graphics.
• $06 oddly uses the bonus stage music. $0D uses the boss music, but is strangely silent in the Master System version.

Unused Music#

Sound Code: 0x8E
Unused jingle of unknown purpose.

Sound Code: 0x9B
While not used here, this track would be recycled (albeit in a lower key) in Sonic Triple Trouble as the Sunset Park boss theme.

Sound Code: 0x83
This song is Gigalopolis Zone from the Master System version. It is in a lower pitch here.

Unused Text#

Like all of Aspect's 8-bit Sonic titles, a basic build string is present at ROM 0xC0:

GG SONIC CHAOS  
  < Ver1.00 >   
1993/09/01 @SEGA
/Aspect Co.,Ltd 

GG SONIC & TAILS
  < Ver1.01 >   
1993/09/07 @SEGA
/Aspect Co.,Ltd 

Debugging Features#

Error Handler#

Another common feature of Aspect's Sonic games, there's a generic error handler routine at ROM 0x70. If the code at that address somehow executes, the game clears the screen, tries to write the message "ERROR", waits for 3 seconds, and then resets. The game doesn't intentionally jump to this code at any point, and it would be of little use anyway because the message will only be intelligible if an ASCII font is already loaded at VRAM 0x2400 (e.g. on the level select screen).

Level Select#

Press Up, Up, Down, Down, Right, Left, Right, Left, Start at the title screen.

Sound Test#

Press Down, Down, Up, Up, Left, Right, Left, Right, 1, 2, Start at the title screen.

The Sonic on this screen is part of an Easter egg: Press Down, Down-Right, Right, 1, and he'll perform a Hadouken!

Regional Differences#

Sega ™#

International	Japan

The Japanese version drops the ™ symbol from the Sega logo.

Title Screen#

International	Japan

The title fonts are different between versions. The larger title screen in the international version moves the "Press Start Button" text down 8 pixels. The international version also gets a trademark to go with its copyright.

Level Titles#

International	Japan

The title card fonts are completely different between regions. Notably, the international version looks similar to that of Sonic the Hedgehog 2 (Game Gear) and does not have Act numbers in its font. The Japanese font is still used for the score card. "Gigalopolis Zone" was shortened to "Gigapolis Zone", even in the Zone Select.

Dr. Robotnik is called "Eggman" in the credits of the Japanese version. Also, the Japanese version uses a combination of Master System and English Game Gear versions' Act 3 layouts. It uses the Master System's layouts for Turquoise Hill Zone and Gigapolis Zone, an altered version of Master System's layout for Sleeping Egg Zone, altered versions of English Game Gear's layouts for Mecha Green Hill Zone and Aqua Planet Zone, and the English Game Gear's layout for Electric Egg Zone.

Sonic & Tails Kattobi Saisoku Technique#

The December 1993 editions of Japanese magazines Shogaku Sannensei, Shogaku Yonensei, and Shogaku Rokunensei (Elementary School Grade 3, Grade 4, and Grade 6, respectively) ran a "Sonic & Tails Kattobi Saisoku Technique" (ソニック&ティルスかっとび最速テクニック or "Sonic & Tails Zooming Best Speed Technique") contest in which readers had to perform a time trial of Turquoise Hill Zone, with four categories for Acts 1 and 2 as either Sonic or Tails. Contestants had to finish either Act with a speed rating greater than 700km/h, pause the game after the rating had finished calculating, and press Up + Left + 1 + 2 to display a six-digit hexadecimal code that would be sent in.

This feature only exists in the Japanese Game Gear version, and is removed from all western releases.

References#