View source for Port Sonic 2 Level Select to Sonic 1

''(Original guide by [[User:DelayHacks|DelayHacks (a.k.a. JustMe)]], updated for the SVN/GitHub disassembly by [[Special:Contributions/The Catman 22|The Catman 22]], Minor refinements by  [[User:DeltaWooloo|DeltaWooloo]] and [https://info.sonicretro.org/User:XPointZPoint XPointZPoint])''

You need to download the level select code made by [[User:Esrael|Esrael]]:
{{Download|title=Sonic 2 Level Select in Sonic 1|version=|file=s2menu.rar}}

and extract it to the root of your dissassembly.

==Hivebrain's 2005 disassembly==
After downloading and extracting the file, go to the end of the main file (sonic1.asm) and you'll find the end of ROM:

<syntaxhighlight lang="asm">
; end of 'ROM'
EndOfRom:


		END
</syntaxhighlight>
Add this include before the "EndOfRom" label:
<syntaxhighlight lang="asm">
	include	"s2_menu.asm"	; Sonic 2 level select
</syntaxhighlight>
Now go to:
<syntaxhighlight lang="asm">
Title_ChkLevSel:
		tst.b	($FFFFFFE0).w	; check	if level select	code is	on
		beq.w	PlayLevel	; if not, play level
		btst	#6,($FFFFF604).w ; check if A is pressed
		beq.w	PlayLevel	; if not, play level
		moveq	#2,d0
		bsr.w	PalLoad2	; load level select pallet
		lea	($FFFFCC00).w,a1
		moveq	#0,d0
		move.w	#$DF,d1
</syntaxhighlight>
and add a jump to "Level_Select_Menu" after the check if A was pressed:
<syntaxhighlight lang="asm">
Title_ChkLevSel:
		tst.b	($FFFFFFE0).w		; check	if level select	code is	on
		beq.w	PlayLevel		; if not, play level
		btst	#6,($FFFFF604).w ; check if A is pressed
		beq.w	PlayLevel		; if not, play level
		jmp	Level_Select_Menu	; if yes, goto Sonic 2 level select	
		moveq	#2,d0
		lea	($FFFFCC00).w,a1
		moveq	#0,d0
		move.w	#$DF,d1
</syntaxhighlight>

Now open "_inc\Pallet pointers.asm" and after this palette:
<syntaxhighlight lang="asm">
	dc.l Pal_Ending
	dc.w $FB00
	dc.w $1F
</syntaxhighlight>
add this:
<syntaxhighlight lang="asm">
	dc.l Menu_Palette; pallet address
	dc.w $FB00	; RAM address
	dc.w $1F	; (pallet length / 2) - 1
</syntaxhighlight>
If you haven't added any new palettes before, proceed.
Otherwise find the palette ID (you can count it from the start of PalPointers, starting palette ID is 0) and change $14 on these lines in "s2_menu.asm" to the ID you have:
<syntaxhighlight lang="asm">
                moveq   #$14, D0
                bsr     Menu_PalLoad1
</syntaxhighlight>
Now you have Sonic 2's level select palette.

Now we need to fix some bugs.
You need to uncomment these lines in "s2_menu.asm" in order to enable the second star at Sound Test:
<syntaxhighlight lang="asm">
;                lea     $FF10(A2), A2
;                move.w  #$001A, (A2)          ; Load "*"
</syntaxhighlight>
Not sure why they were commented out though.

Now to fix some assembling errors you should fix $FF10 from the lines above to $FFFFFF10 and you may see "$FBA0" on the line before "Menu_Clear_Act_x" label, change it to "$FFFFFBA0".

==SVN/GitHub disassembly==

After downloading and extracting the file, go to the end of the main file (sonic1.asm) and you'll find the end of ROM:

<syntaxhighlight lang="asm">
; end of 'ROM'
EndOfRom:


		END
</syntaxhighlight>
Add this include before the "EndOfRom" label:
<syntaxhighlight lang="asm">
	include	"s2_menu.asm"	; Sonic 2 level select
</syntaxhighlight>
Now go to:
<syntaxhighlight lang="asm">
Title_ChkLevSel:
		tst.b	(f_levselcheat).w ; check if level select code is on
		beq.w	PlayLevel	; if not, play level
		btst	#bitA,(v_jpadhold1).w ; check if A is pressed
		beq.w	PlayLevel	; if not, play level

		moveq	#palid_LevelSel,d0
		bsr.w	PalLoad2	; load level select palette
		lea	(v_hscrolltablebuffer).w,a1
		moveq	#0,d0
		move.w	#$DF,d1
</syntaxhighlight>
and add a jump to "Level_Select_Menu" after the check if A was pressed:
<syntaxhighlight lang="asm">
Title_ChkLevSel:
		tst.b	(f_levselcheat).w ; check if level select code is on
		beq.w	PlayLevel	; if not, play level
		btst	#bitA,(v_jpadhold1).w ; check if A is pressed
		beq.w	PlayLevel	; if not, play level
		jmp	Level_Select_Menu; Go to Sonic 2 Level Select
		moveq	#palid_LevelSel,d0
		bsr.w	PalLoad2	; load level select palette
		lea	(v_hscrolltablebuffer).w,a1
		moveq	#0,d0
		move.w	#$DF,d1
</syntaxhighlight>

Now open "_inc\Palette pointers.asm" and after this palette:
<syntaxhighlight lang="asm">
	ptr_Pal_Ending:		palp	Pal_Ending,v_pal_dry,$40		; $13 (19) - ending sequence
</syntaxhighlight>
add this:
<syntaxhighlight lang="asm">
	ptr_Pal_Menu:		palp	Pal_Menu,v_pal_dry,$40		; 2 - level select
</syntaxhighlight>
If you haven't added any new palettes before, proceed.
Otherwise find the palette ID (you can count it from the start of PalPointers, starting palette ID is 0) and change $14 on these lines in "s2_menu.asm" to the ID you have:
<syntaxhighlight lang="asm">
                moveq   #$14, D0
                bsr     Menu_PalLoad1
</syntaxhighlight>
Now you have Sonic 2's level select palette.

Now we need to fix some bugs.
You need to uncomment these lines in "s2_menu.asm" in order to enable the second star at Sound Test:
<syntaxhighlight lang="asm">
;                lea     $FF10(A2), A2
;                move.w  #$001A, (A2)          ; Load "*"
</syntaxhighlight>
Not sure why they were commented out though.

Now to fix some assembling errors you should fix $FF10 from the lines above to $FFFFFF10 and you may see "$FBA0" on the line before "Menu_Clear_Act_x" label, change it to "$FFFFFBA0".

Now open "s2_menu.asm" and change this code:

<syntaxhighlight lang="asm">
Menu_Palette:
                incbin  'data\menu\menu.pal' 
Menu_ClearScreen:
                jmp     ClearScreen
Menu_ShowVDPGraphics:                
                jmp     ShowVDPGraphics                
Menu_NemesisDec: 
                jmp     NemDec  
Menu_LoadPLC2:      
                jmp     LoadPLC2
Menu_RunPLC:                    
                jmp     RunPLC_RAM                           
Menu_EnigmaDec
                jmp     EniDec
Menu_Pal_FadeTo:
                jmp     Pal_FadeTo
Menu_Pal_FadeFrom:
                jmp     Pal_FadeFrom     
Menu_Play_Music:
                jmp     PlaySound  
Menu_PalLoad1:
                jmp     PalLoad1
Menu_DelayProgram:
                jmp     DelayProgram
</syntaxhighlight>

to this:
<syntaxhighlight lang="asm">
Pal_Menu:
                incbin  'data\menu\menu.pal'    
Menu_ClearScreen:
                jmp     ClearScreen
Menu_ShowVDPGraphics:                
                jmp     TilemapToVRAM                
Menu_NemesisDec: 
                jmp     NemDec  
Menu_LoadPLC2:      
                jmp     NewPLC
Menu_RunPLC:                    
                jmp     RunPLC                          
Menu_EnigmaDec
                jmp     EniDec
Menu_Pal_FadeTo:
                jmp     PaletteFadeIn
Menu_Pal_FadeFrom:
                jmp     PaletteFadeOut     
Menu_Play_Music:
                jmp     PlaySound  
Menu_PalLoad1:
                jmp     PalLoad1
Menu_DelayProgram:
                jmp     WaitForVBla
</syntaxhighlight>

==Other==

===Changing sounds and editing zone names===

Now go to "s2_menu.asm" you can find these lines of code around the start of the file:
<syntaxhighlight lang="asm">
Level_Select_Menu_snd   = $0081
Emerald_Snd             = $0093
Ring_Snd                = $00B5
Volume_Down             = $00E0
Stop_Sound              = $00E4
</syntaxhighlight>
Level_Select_Menu_snd is the music played in the menu, Emerald_Snd is the sound played if all emeralds code is entered, Ring_Snd is the sound played if debug mode code is entered.

To edit zone names, find label "Menu_Level_Select_Text":
<syntaxhighlight lang="asm">
                dc.b    $0E, _G, _R, _E, _E, _N, __, _H, _I, _L, _L, __, __, __, __, __
                dc.b    $0E, _L, _A, _B, _Y, _R, _I, _N, _T, _H, __, __, __, __, __, __
                dc.b    $0E, _M, _A, _R, _B, _L, _E, __, __, __, __, __, __, __, __, __
                dc.b    $0E, _S, _P, _R, _I, _N, _G, __, _Y, _A, _R, _D, __, __, __, __
                dc.b    $0E, _S, _T, _A, _R, __, _L, _I, _G, _H, _T, __, __, __, __, __
                dc.b    $0E, _S, _C, _R, _A, _P, __, _B, _R, _A, _I, _N, __, __, __, __
                dc.b    $0E, _F, _I, _N, _A, _L, __, __, __, __, __, __, __, __, __, __   
                dc.b    $0E, _S, _P, _E, _C, _I, _A, _L, __, _S, _T, _A, _G, _E, __, __
                dc.b    $0E, _E, _N, _D, _I, _N, _G, __, _S, _E, _Q, _U, _E, _N, _C, _E
                dc.b    $0E, _S, _O, _U, _N, _D, __, _T, _E, _S, _T, __, __, _st,__, __ 
</syntaxhighlight>
Now you can edit the text in the level select.

===Fixing Level Order in Level Select Menu===
To Correct the Level Order , find this piece of code:
<syntaxhighlight lang="asm">
Menu_Level_Select_Array:
                dc.w    $0000, $0001, $0002
                dc.w    $0100, $0101, $0102
                dc.w    $0200, $0201, $0202
                dc.w    $0300, $0301, $0302
                dc.w    $0400, $0401, $0402
                dc.w    $0500, $0501, $0103
                dc.w    $0502, $4000, $0600
                dc.w    $FFFF
</syntaxhighlight>
And change it to this:
<syntaxhighlight lang="asm">
Menu_Level_Select_Array:
                dc.w    $0000, $0001, $0002	;GHZ
                dc.w    $0200, $0201, $0202	;MZ
                dc.w    $0400, $0401, $0402	;SYZ				
                dc.w    $0100, $0101, $0102 ;LZ
                dc.w    $0300, $0301, $0302	;SLZ
                dc.w    $0500, $0501, $0103	;SBZ
                dc.w    $0502, $4000, $0600	
                dc.w    $FFFF
</syntaxhighlight>
Now for the Level Select text, find this:
<syntaxhighlight lang="asm">
Menu_Level_Select_Text: 
                dc.b    $0E, _G, _R, _E, _E, _N, __, _H, _I, _L, _L, __, __, __, __, __
                dc.b    $0E, _L, _A, _B, _Y, _R, _I, _N, _T, _H, __, __, __, __, __, __
                dc.b    $0E, _M, _A, _R, _B, _L, _E, __, __, __, __, __, __, __, __, __
                dc.b    $0E, _S, _P, _R, _I, _N, _G, __, _Y, _A, _R, _D, __, __, __, __
                dc.b    $0E, _S, _T, _A, _R, __, _L, _I, _G, _H, _T, __, __, __, __, __
                dc.b    $0E, _S, _C, _R, _A, _P, __, _B, _R, _A, _I, _N, __, __, __, __
                dc.b    $0E, _F, _I, _N, _A, _L, __, __, __, __, __, __, __, __, __, __   
                dc.b    $0E, _S, _P, _E, _C, _I, _A, _L, __, _S, _T, _A, _G, _E, __, __
                dc.b    $0E, _E, _N, _D, _I, _N, _G, __, _S, _E, _Q, _U, _E, _N, _C, _E
                dc.b    $0E, _S, _O, _U, _N, _D, __, _T, _E, _S, _T, __, __, _st,__, __     
</syntaxhighlight>
And change it to this:
<syntaxhighlight lang="asm">
Menu_Level_Select_Text: 
                dc.b    $0E, _G, _R, _E, _E, _N, __, _H, _I, _L, _L, __, __, __, __, __
                dc.b    $0E, _M, _A, _R, _B, _L, _E, __, __, __, __, __, __, __, __, __
                dc.b    $0E, _S, _P, _R, _I, _N, _G, __, _Y, _A, _R, _D, __, __, __, __
                dc.b    $0E, _L, _A, _B, _Y, _R, _I, _N, _T, _H, __, __, __, __, __, __
                dc.b    $0E, _S, _T, _A, _R, __, _L, _I, _G, _H, _T, __, __, __, __, __
                dc.b    $0E, _S, _C, _R, _A, _P, __, _B, _R, _A, _I, _N, __, __, __, __
                dc.b    $0E, _F, _I, _N, _A, _L, __, __, __, __, __, __, __, __, __, __   
                dc.b    $0E, _S, _P, _E, _C, _I, _A, _L, __, _S, _T, _A, _G, _E, __, __
                dc.b    $0E, _E, _N, _D, _I, _N, _G, __, _S, _E, _Q, _U, _E, _N, _C, _E
                dc.b    $0E, _S, _O, _U, _N, _D, __, _T, _E, _S, _T, __, __, _st,__, __ 
</syntaxhighlight>
'''Now you have the Rev01 level select order'''

===Changing zone icons===
If you wish to change zone icons you need to change the data at "Menu_Icon_List" label in "s2_menu.asm":
<syntaxhighlight lang="asm">
Menu_Icon_List:
                dc.b    $00, $00, $00, $0E, $0E, $0E, $06, $06, $06, $0B, $0B, $0B, $0D, $0D, $0D, $09
                dc.b    $09, $09, $04, $10, $0F, $11
</syntaxhighlight>

===Editing cheats===
To edit "debug mode" code go to the label "Code_Debug_Mode:".
To edit "all emeralds" code go to label "Code_All_Emeralds:"

That's all. All permissions for this level select code goes to [[User:Esrael|Esrael]]. Result:

[[File:S2levelselectInS1.png|320px]]

'''NOTE: If you attempt to play a sound that is place 14 or above if you haven't [[SCHG_How-to:Expand_the_Sonic_1_sound_index|fixed the sound test]], the game will throw an illegal instruction'''
[[File:Sonic2LevelSelectInSonic1HowToWarning.png|320px]]

{{S1Howtos}}