SONIC 1 LEVEL ORDER EDITING GUIDE
CRE FRI MAR 022 002
VERSION 1.0
BY LUIGI_LINK
FOR: GM 00001009-00 (American Sonic 1)
     GM 00004009-01 (Japanese revised Sonic 1)

I'm back again with my level order editing guides. This time it's for Sonic 1, an often neglected game that should be cracked more. I will explain formats and addresses more strictly in this guide, meaning it's a little less friendly for newbies.

REGULAR LEVEL ORDER (for reference)

Green Hill Zone  Act 1 (00 00)
Green Hill Zone  Act 2 (00 01)
Green Hill Zone  Act 3 (00 02)
Marble Zone      Act 1 (02 00)
Marble Zone      Act 2 (02 01)
Marble Zone      Act 3 (02 02)
Spring Yard Zone Act 1 (04 00)
Spring Yard Zone Act 2 (04 01)
Spring Yard Zone Act 3 (04 02)
Labyrinth Zone   Act 1 (01 00)
Labyrinth Zone   Act 2 (01 01)
Labyrinth Zone   Act 3 (01 02)
Star Light Zone  Act 1 (03 00)
Star Light Zone  Act 2 (03 01)
Star Light Zone  Act 3 (03 02)
Scrap Brain Zone Act 1 (05 00)
Scrap Brain Zone Act 2 (05 01)
Scrap Brain Zone Act 3 (01 03)
Final Zone             (05 02)

Notice the last two are different from the format. SBZ Act 3 points to LZ Act 4, and FZ points to SBZ 3. It makes sense when you think about it. SBZ Act 3 uses LZ tiles.

LEVEL TAGS

Act 1 is 00, Act 2 is 01, Act 3 is 02.

00 - Green Hill Zone
01 - Labyrinth Zone (01 03 is Scrap Brain 3) 
02 - Marble Zone 
03 - Star Light Zone 
04 - Spring Yard Zone 
05 - Scrap Brain Zone (05 02 is Final Zone) 

STARTING LEVEL

0x00305E - Starting level for (UE) (press start on title screen)
0x003038 - Starting level for (J)  (press start on title screen)

If you've looked at Sonic 2's transitions, you would notice that they use the format: 31 FC xx xx FE 10. This is how these were found. A warning, though: If you change the starting level to anything other than Green Hill Zone, the title screen will mess up. So if you're willing to sacrafice that fact, go right ahead.

ORDER OF THE LEVELS LIST

0x00C6F4 - Order of the levels list (UE) 
0x00336C - Order of the levels list (J)

Contrary to there being three acts for every zone it seems, there are four act listings for each zone. This is because of Scrap Brain Zone Act 3 - which is really Labyrinth Zone Act 4. Zones that don't have an act 4 will have 00 00 at its listing. So a whole zone turns out to be 2 DWORDS, or 4 WORDS. I do not know what yet makes it soft reset, if it all, at this time.

TRANSITIONS

SBZ 2 to SBZ 3  13366 - 0103 (UE)
SBZ 2 to SBZ 3  14A38 - 0103 (J)
SBZ 3 to FINAL    6F82 - 0502 (UE)
SBZ 3 to FINAL    7FCA - 0502 (J)

Pretty much self-explanitory. Again, these don't use the level order list because they fade out to the next level, so these are if you want to change where they go.

SPECIAL THANKS TO:

Esrael
    (U) transition addresses
Saxman
    Level order addresses (but they were off a little bit)