Sonic 2 (Simon Wai Prototype) Level Select in Sonic 1
From Sonic Retro
you probably wonder why sonic2 beta has that level select that looks almost like the sonic1 level select and how sonic2 nick arcade prototype has one that is the sonic1 level select, well, that is what we are going to make the one in sonic1 behave like.
Overview
First, lets look at an overview of what our level select code looks like in a normal sonic1 (It is from the Hivebrain disassembly): <asm>
- ---------------------------------------------------------------------------
- Level Select
- ---------------------------------------------------------------------------
LevelSelect: move.b #4,($FFFFF62A).w bsr.w DelayProgram bsr.w LevSelControls bsr.w RunPLC_RAM tst.l ($FFFFF680).w bne.s LevelSelect andi.b #$F0,($FFFFF605).w ; is A, B, C, or Start pressed? beq.s LevelSelect ; if not, branch move.w ($FFFFFF82).w,d0 cmpi.w #$14,d0 ; have you selected item $14 (sound test)? bne.s LevSel_Level_SS ; if not, go to Level/SS subroutine move.w ($FFFFFF84).w,d0 addi.w #$80,d0 tst.b ($FFFFFFE3).w ; is Japanese Credits cheat on? beq.s LevSel_NoCheat ; if not, branch cmpi.w #$9F,d0 ; is sound $9F being played? beq.s LevSel_Ending ; if yes, branch cmpi.w #$9E,d0 ; is sound $9E being played? beq.s LevSel_Credits ; if yes, branch
LevSel_NoCheat: cmpi.w #$94,d0 ; is sound $80-$94 being played? bcs.s LevSel_PlaySnd ; if yes, branch cmpi.w #$A0,d0 ; is sound $95-$A0 being played? bcs.s LevelSelect ; if yes, branch
LevSel_PlaySnd: bsr.w PlaySound_Special bra.s LevelSelect
- ===========================================================================
LevSel_Ending: ; XREF: LevelSelect move.b #$18,($FFFFF600).w ; set screen mode to $18 (Ending) move.w #$600,($FFFFFE10).w ; set level to 0600 (Ending) rts
- ===========================================================================
LevSel_Credits: ; XREF: LevelSelect move.b #$1C,($FFFFF600).w ; set screen mode to $1C (Credits) move.b #$91,d0 bsr.w PlaySound_Special ; play credits music move.w #0,($FFFFFFF4).w rts
- ===========================================================================
LevSel_Level_SS: ; XREF: LevelSelect add.w d0,d0 move.w LSelectPointers(pc,d0.w),d0 ; load level number bmi.w LevelSelect cmpi.w #$700,d0 ; check if level is 0700 (Special Stage) bne.s LevSel_Level ; if not, branch move.b #$10,($FFFFF600).w ; set screen mode to $10 (Special Stage) clr.w ($FFFFFE10).w ; clear level move.b #3,($FFFFFE12).w ; set lives to 3 moveq #0,d0 move.w d0,($FFFFFE20).w ; clear rings move.l d0,($FFFFFE22).w ; clear time move.l d0,($FFFFFE26).w ; clear score rts
- ===========================================================================
LevSel_Level: ; XREF: LevSel_Level_SS andi.w #$3FFF,d0 move.w d0,($FFFFFE10).w ; set level number
PlayLevel: ; XREF: ROM:00003246�j ... move.b #$C,($FFFFF600).w ; set screen mode to $0C (level) move.b #3,($FFFFFE12).w ; set lives to 3 moveq #0,d0 move.w d0,($FFFFFE20).w ; clear rings move.l d0,($FFFFFE22).w ; clear time move.l d0,($FFFFFE26).w ; clear score move.b d0,($FFFFFE16).w ; clear special stage number move.b d0,($FFFFFE57).w ; clear emeralds move.l d0,($FFFFFE58).w ; clear emeralds move.l d0,($FFFFFE5C).w ; clear emeralds move.b d0,($FFFFFE18).w ; clear continues move.b #$E0,d0 bsr.w PlaySound_Special ; fade out music rts
- ===========================================================================
- ---------------------------------------------------------------------------
- Level select - level pointers
- ---------------------------------------------------------------------------
LSelectPointers: binclude misc\ls_point.bin align 2
- ---------------------------------------------------------------------------
- Level select codes
- ---------------------------------------------------------------------------
LevelSelectCode_J: binclude misc\ls_jcode.bin align 2
LevelSelectCode_US: binclude misc\ls_ucode.bin align 2
- ===========================================================================
</asm>
Notice anything here?
Button Fix, Part 1
A lot of stuff we really do not need, as well as the fast that all buttons that are not the D-Pad seem to be used to play a sound or select a level. Lets fix that. <asm> LevelSelect: move.b #4,($FFFFF62A).w bsr.w DelayProgram bsr.w LevSelControls bsr.w RunPLC_RAM tst.l ($FFFFF680).w bne.s LevelSelect andi.b #$F0,($FFFFF605).w ; is A, B, C, or Start pressed? beq.s LevelSelect ; if not, branch move.w ($FFFFFF82).w,d0 cmpi.w #$14,d0 ; have you selected item $14 (sound test)? bne.s LevSel_Level_SS ; if not, go to Level/SS subroutine move.w ($FFFFFF84).w,d0 addi.w #$80,d0 tst.b ($FFFFFFE3).w ; is Japanese Credits cheat on? beq.s LevSel_NoCheat ; if not, branch cmpi.w #$9F,d0 ; is sound $9F being played? beq.s LevSel_Ending ; if yes, branch cmpi.w #$9E,d0 ; is sound $9E being played? beq.s LevSel_Credits ; if yes, branch
LevSel_NoCheat: cmpi.w #$94,d0 ; is sound $80-$94 being played? bcs.s LevSel_PlaySnd ; if yes, branch cmpi.w #$A0,d0 ; is sound $95-$A0 being played? bcs.s LevelSelect ; if yes, branch
LevSel_PlaySnd: bsr.w PlaySound_Special bra.s LevelSelect </asm>
we do not need the japanese credits code, removed that junk. as for the levels, we want to start them with the start button but not exclusively just the start button, so an andi would be used there. Also, we want start to exit back to the sega screen, and why not some nice music? only B or C should play something on the sound test.
the results should look like this:
<asm> LevelSelect: move.b #4,($FFFFF62A).w bsr.w DelayProgram bsr.w LevSelControls bsr.w RunPLC_RAM tst.l ($FFFFF680).w bne.s LevelSelect move.w ($FFFFFF82).w,d0 cmpi.w #$14,d0 ; have you selected item $14 (sound test)? bne.s LevSelLevCheckStart; if not, go to Level/SS subroutine cmpi.b #$80,($FFFFF605).w ; is Start pressed? beq.s LevSelStartPress ; if true, branch cmpi.b #$20,($FFFFF605).w ; is B pressed? beq.s LevSelBCPress ; if not, branch cmpi.b #$10,($FFFFF605).w ; is C pressed? beq.s LevSelBCPress ; if not, branch bra.s LevelSelect
- ===========================================================================
LevSelLevCheckStart: ; XREF: LevelSelect andi.b #$80,($FFFFF605).w ; is Start pressed? beq.s LevelSelect ; if not, branch bra.s LevSel_Level_SS
LevSelBCPress: ; XREF: LevelSelect move.w ($FFFFFF84).w,d0 addi.w #$80,d0 cmpi.w #$94,d0 ; is sound $80-$94 being played? bcs.s LevSel_PlaySnd ; if yes, branch cmpi.w #$A0,d0 ; is sound $95-$A0 being played? bcs.s LevelSelect ; if yes, branch
LevSel_PlaySnd: bsr.w PlaySound_Special bra.s LevelSelect
LevSelStartPress: ; XREF: LevelSelect move.b #$00,$FFFFF600 jmp MainGameLoop ;go to sega screen
</asm>
Level Select Music Fix
That fixes the level select so that it runs levels in a sonic2 manner, but it doesnt fix the music. Lets do thar now.
find: <asm> Title_ClrVram: move.l d0,(a6) dbf d1,Title_ClrVram ; fill VRAM with 0
bsr.w LevSelTextLoad </asm>
and add under dbf d1,Title_ClrVram ; fill VRAM with 0, these lines: <asm> move.b #$81,d0 jsr PlaySound </asm> replace #$81 with your choice of song.
the result should look like: <asm> Title_ClrVram: move.l d0,(a6) dbf d1,Title_ClrVram ; fill VRAM with 0 move.b #$81,d0 jsr PlaySound bsr.w LevSelTextLoad </asm> Green Hill Zone music at the level select, how lovely. on the other hand, if you plan on using my Sonic2 Driver port, try using music number $91 and PlayMusic as opposed to PlaySound.
Button Fix, Part 2
As you already know, the A button is not yet fixed, time to fix that button:
First We will have to edit the "LevSel_SndTest" routine. $C (left and right) will not work for detecting an A button. we will need $4C (A/Left/Right) instead, so look in our function for: <asm> LevSel_SndTest: ; XREF: LevSelControls cmpi.w #$14,($FFFFFF82).w ; is item $14 selected? bne.s LevSel_NoMove ; if not, branch move.b ($FFFFF605).w,d1 andi.b #$C,d1 ; is left/right pressed? </asm>
and change it to read out: <asm> LevSel_SndTest: ; XREF: LevSelControls cmpi.w #$14,($FFFFFF82).w ; is item $14 selected? bne.s LevSel_NoMove ; if not, branch move.b ($FFFFF605).w,d1 andi.b #$4C,d1 ; is left/right/A pressed?
</asm> instead.
Now we can start working on adding the routine to handle the A button and increase the 16's ($10) part of the sound test:
locate: <asm> beq.s LevSel_NoMove ; if not, branch move.w ($FFFFFF84).w,d0 </asm>
and add below: <asm> btst #6,d1 ; is A pressed? bne.s LevSel_A ; if not, branch </asm>
now locate: <asm> bcc.s LevSel_Right moveq #$4F,d0 ; if sound test moves below 0, set to $4F </asm>
and add this routine under it to add A button support to the level select: <asm> LevSel_A: btst #6,d1 ; is A button pressed? beq.s LevSel_Right ; if not, branch add.w #16,d0 ; add $10 to sound test </asm>
now the sonic1 level select will behave exactly like that of the one in sonic2 (simon wai prototype, except for night mode and split screen, those can be added manually if you get such a system working). Enjoy your alternative level select :)