How To: Convert Sonic 1's Level Select to use ASCII

While working with Sonic 1, I got tired of having to edit the level select text in a Hex editor, when it's contents is just plain text in a non-standard encoding, I decided enough was enough, and set out to convert Sonic 1's level select to use standard ASCII text encoding. After a very small amount of work, I decided to compile it into a guide.

This guide is for the SVN disassembly of Sonic 1. It should be VERY easy to port to other disassemblies as the code changes make no use of macros or equates.

First, download this file (menutext.bin) and replace the existing file in the "artunc" folder. This is the Sonic 2's menu font uncompressed to work in Sonic 1. It's what I use in my hack, and it's what my code expects.

Now open Sonic.asm and find the LevelMenuText label and replace this:

Code:

LevelMenuText:    if Revision=0
        incbin    "miscLevel Select Text.bin"
        else
        incbin    "miscLevel Select Text (JP1).bin"
        endc
        even

With this:

Code:

LevelMenuText:   if Revision=0
    dc.b    "GREEN HILL ZONE  STAGE 1"
        dc.b    "                 STAGE 2"
        dc.b    "                 STAGE 3"
        dc.b    "LABYRINTH        STAGE 1"
        dc.b    "                 STAGE 2"
        dc.b    "                 STAGE 3"
        dc.b    "MARBLE ZONE      STAGE 1"
        dc.b    "                 STAGE 2"
        dc.b    "                 STAGE 3"
        dc.b    "STAR LIGHT ZONE  STAGE 1"
        dc.b    "                 STAGE 2"
        dc.b    "                 STAGE 3"
        dc.b    "SPRING YARD ZONE STAGE 1"
        dc.b    "                 STAGE 2"
        dc.b    "                 STAGE 3"
        dc.b    "SCRAP BRAIN ZONE STAGE 1"
        dc.b    "                 STAGE 2"
        dc.b    "                 STAGE 3"
        dc.b    "FINAL ZONE              "            
        dc.b    "SPECIAL STAGE           "          
        dc.b    "SOUND TEST              "              
        even
        else
        dc.b    "GREEN HILL ZONE  STAGE 1"
        dc.b    "                 STAGE 2"
        dc.b    "                 STAGE 3"
        dc.b    "MARBLE ZONE      STAGE 1"
        dc.b    "                 STAGE 2"
        dc.b    "                 STAGE 3"
        dc.b    "SPRING YARD ZONE STAGE 1"
        dc.b    "                 STAGE 2"
        dc.b    "                 STAGE 3"
        dc.b    "LABYRINTH        STAGE 1"
        dc.b    "                 STAGE 2"
        dc.b    "                 STAGE 3"
        dc.b    "STAR LIGHT ZONE  STAGE 1"
        dc.b    "                 STAGE 2"
        dc.b    "                 STAGE 3"
        dc.b    "SCRAP BRAIN ZONE STAGE 1"
        dc.b    "                 STAGE 2"
        dc.b    "                 STAGE 3"
        dc.b    "FINAL ZONE              "            
        dc.b    "SPECIAL STAGE           "          
        dc.b    "SOUND TEST              "        
        endc

As you can see, this is much easier as you can just edit the text directly.

Now we need to modify Sonic 1 to actually understand this text format, so scroll upwards to LevSel_CharOk: and replace this:

Code:

LevSel_CharOk:
        add.w    d3,d0        ; combine char with VRAM setting
        move.w    d0,(a6)        ; send to VRAM
        dbf        d2,LevSel_LineLoop
        rts    

Code:

LevSel_CharOk:
        cmp.w    #$40, d0    ; Check for $40 (End of ASCII number area)
        blt.s        @notText    ; If this is not an ASCII text character, branch
        sub.w    #$3,d0        ; Subtract an extra 3 (Compensate for missing characters in the font)
    @notText:
        sub.w    #$30,d0        ; Subtract #$33 (Convert to S2 font from ASCII)
        add.w    d3,d0        ; combine char with VRAM setting
        move.w    d0,(a6)        ; send to VRAM
        dbf        d2,LevSel_LineLoop
        rts   

Now to fix the Sound Test numbers, find LevSel_ChgSnd and change this line:

Code:

        addi.b #7,d0 ; use alpha characters

To this:

Code:

        addi.b #4,d0 ; use alpha characters

The debug text and error message strings need the same fix, but this is a task left to the reader.

There is one final problem, the Sonic 2 font requires a different colour palette than Sonic 1 uses, so take this file, and place it in the palette folder, overwriting the existing one.

And you are done, build your rom and enjoy the easy to edit text.

 

 

The Sound Test numbers are messed up!

 

Sometimes I wonder if I should just release the converter I wrote years ago when I worked on my hack, it allows to convert back and forth from the Sonic 1 charset to standard ASCII and vice-versa.

 

please do - sounds useful

 

Ok.