SCHG How-to:Port the REV01 Background Effects

(Original guide by jman2050)

Looking at the REV01 version of Sonic 1, I can see why it's Rev01. They pretty much completely overhauled the entire BG deformation part of the engine. The drawing system has been changed (and from what I've seen, more similar to the way Sonic 2 does things) and the deformation data for every level has been changed to fit this new code. Also, in every level besides SBZ2, it was used to enhance the deformation effects. To see the difference in your own Sonic 1 rom, you'll have to do the following...

Steps

Step 1

First, we'll do the easiest change. Go to label Obj0A_WobbleData in Hivebrain's 2005 disassembly and replace the entire block with this: <asm>Obj0A_WobbleData: dc.b 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2 dc.b 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3 dc.b 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 2, 2, 2 dc.b 2, 2, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, -1, -1 dc.b -1, -1, -1, -2, -2, -2, -2, -2, -3, -3, -3, -3, -3 dc.b -3, -3, -4, -4, -4, -4, -4, -4, -4, -4, -4, -4, -4 dc.b -4, -4, -4, -4, -4, -4, -4, -4, -4, -4, -4, -4, -4 dc.b -4, -4, -4, -4, -4, -3, -3, -3, -3, -3, -3, -3, -2 dc.b -2, -2, -2, -2, -1, -1, -1, -1, -1 dc.b 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2 dc.b 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3 dc.b 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 2, 2, 2 dc.b 2, 2, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, -1, -1 dc.b -1, -1, -1, -2, -2, -2, -2, -2, -3, -3, -3, -3, -3 dc.b -3, -3, -4, -4, -4, -4, -4, -4, -4, -4, -4, -4, -4 dc.b -4, -4, -4, -4, -4, -4, -4, -4, -4, -4, -4, -4, -4 dc.b -4, -4, -4, -4, -4, -3, -3, -3, -3, -3, -3, -3, -2 dc.b -2, -2, -2, -2, -1, -1, -1, -1, -1</asm>

The programmers extended this array so it would also be usable by the deformation data even though it was designed to be used by the water bubbles.

Step 2

Next, we'll do the BGScroll data. Go to BGScroll_GHZ in the disassembly. Replace everything from there until the end of BGScroll_End with the following: <asm>BgScroll_GHZ: ; XREF: BgScroll_Index clr.l ($FFFFF708).w clr.l ($FFFFF70C).w clr.l ($FFFFF714).w clr.l ($FFFFF71C).w lea ($FFFFA800).w,a2 clr.l (a2)+ clr.l (a2)+ clr.l (a2)+ rts

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BgScroll_LZ: ; XREF: BgScroll_Index asr.l #1,d0 move.w d0,($FFFFF70C).w rts

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BgScroll_MZ: ; XREF: BgScroll_Index rts

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BgScroll_SLZ: ; XREF: BgScroll_Index asr.l #1,d0 addi.w #$C0,d0 move.w d0,($FFFFF70C).w clr.l ($FFFFF708).w rts

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BgScroll_SYZ: ; XREF: BgScroll_Index asl.l #4,d0 move.l d0,d2 asl.l #1,d0 add.l d2,d0 asr.l #8,d0 addq.w #1,d0 move.w d0,($FFFFF70C).w clr.l ($FFFFF708).w rts

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BgScroll_SBZ: ; XREF: BgScroll_Index andi.w #$7F8,d0 asr.w #3,d0 addq.w #1,d0 move.w d0,($FFFFF70C).w rts

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BgScroll_End: ; XREF: BgScroll_Index move.w ($FFFFF700).w,d0 asr.w #1,d0 move.w d0,($FFFFF708).w move.w d0,($FFFFF710).w asr.w #2,d0 move.w d0,d1 add.w d0,d0 add.w d1,d0 move.w d0,($FFFFF718).w clr.l ($FFFFF70C).w clr.l ($FFFFF714).w clr.l ($FFFFF71C).w lea ($FFFFA800).w,a2 clr.l (a2)+ clr.l (a2)+ clr.l (a2)+ rts </asm>

The starting deformation data for every stage needed to be changed. To be precise, it prevents bugs that occur in the scrolling in SBZ and SYZ, and prevents a bug that causes GHZ's bg not to appear at all.

Step 3

Next, we'll do the deformation data itself. Go to Deform_GHZ, and replace everything from there until the end of Deform_SBZ, straight down (right before ScrollHoriz) with the following: <asm>Deform_GHZ: move.w ($FFFFF73A).w,d4 ext.l d4 asl.l #5,d4 move.l d4,d1 asl.l #1,d4 add.l d1,d4 moveq #0,d6 bsr.w ScrollBlock6 move.w ($FFFFF73A).w,d4 ext.l d4 asl.l #7,d4 moveq #0,d6 bsr.w ScrollBlock5 lea ($FFFFCC00).w,a1 move.w ($FFFFF704).w,d0 andi.w #$7FF,d0 lsr.w #5,d0 neg.w d0 addi.w #$20,d0 ; ' ' bpl.s Deform_GHZ_1 moveq #0,d0

Deform_GHZ_1: ; XREF: Deform_GHZ move.w d0,d4 move.w d0,($FFFFF618).w move.w ($FFFFF700).w,d0 cmpi.b #4,($FFFFF600).w bne.s Deform_GHZ_2 moveq #0,d0

Deform_GHZ_2: ; XREF: Deform_GHZ neg.w d0 swap d0 lea ($FFFFA800).w,a2 addi.l #$10000,(a2)+ addi.l #$C000,(a2)+ addi.l #$8000,(a2)+ move.w ($FFFFA800).w,d0 add.w ($FFFFF718).w,d0 neg.w d0 move.w #$1F,d1 sub.w d4,d1 bcs.s Deform_GHZ_4

Deform_GHZ_3: ; XREF: Deform_GHZ move.l d0,(a1)+ dbf d1,Deform_GHZ_3

Deform_GHZ_4: ; XREF: Deform_GHZ move.w ($FFFFA804).w,d0 add.w ($FFFFF718).w,d0 neg.w d0 move.w #$F,d1

Deform_GHZ_5: ; XREF: Deform_GHZ move.l d0,(a1)+ dbf d1,Deform_GHZ_5 move.w ($FFFFA808).w,d0 add.w ($FFFFF718).w,d0 neg.w d0 move.w #$F,d1

Deform_GHZ_6: ; XREF: Deform_GHZ move.l d0,(a1)+ dbf d1,Deform_GHZ_6 move.w #$2F,d1 ; '/' move.w ($FFFFF718).w,d0 neg.w d0

Deform_GHZ_7: ; XREF: Deform_GHZ move.l d0,(a1)+ dbf d1,Deform_GHZ_7 move.w #$27,d1 ; move.w ($FFFFF710).w,d0 neg.w d0

Deform_GHZ_8: ; XREF: Deform_GHZ move.l d0,(a1)+ dbf d1,Deform_GHZ_8 move.w ($FFFFF710).w,d0 move.w ($FFFFF700).w,d2 sub.w d0,d2 ext.l d2 asl.l #8,d2 divs.w #$68,d2 ; 'h' ext.l d2 asl.l #8,d2 moveq #0,d3 move.w d0,d3 move.w #$47,d1 ; 'G' add.w d4,d1

Deform_GHZ_9: ; XREF: Deform_GHZ move.w d3,d0 neg.w d0 move.l d0,(a1)+ swap d3 add.l d2,d3 swap d3 dbf d1,Deform_GHZ_9 rts

End of function Deform_GHZ

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Deform_LZ: move.w ($FFFFF73A).w,d4 ext.l d4 asl.l #7,d4 move.w ($FFFFF73C).w,d5 ext.l d5 asl.l #7,d5 bsr.w ScrollBlock1 move.w ($FFFFF70C).w,($FFFFF618).w lea (LZ_Wave_Data).l,a3 lea (Obj0A_WobbleData).l,a2 move.b ($FFFFF7D8).w,d2 move.b d2,d3 addi.w #$80,($FFFFF7D8).w ; '€' add.w ($FFFFF70C).w,d2 andi.w #$FF,d2 add.w ($FFFFF704).w,d3 andi.w #$FF,d3 lea ($FFFFCC00).w,a1 move.w #$DF,d1 ; 'ß' move.w ($FFFFF700).w,d0 neg.w d0 move.w d0,d6 swap d0 move.w ($FFFFF708).w,d0 neg.w d0 move.w ($FFFFF646).w,d4 move.w ($FFFFF704).w,d5

Deform_LZ_1: ; XREF: Deform_LZ cmp.w d4,d5 bge.s Deform_LZ_2 move.l d0,(a1)+ addq.w #1,d5 addq.b #1,d2 addq.b #1,d3 dbf d1,Deform_LZ_1 rts

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Deform_LZ_2: ; XREF: Deform_LZ move.b (a3,d3.w),d4 ext.w d4 add.w d6,d4 move.w d4,(a1)+ move.b (a2,d2.w),d4 ext.w d4 add.w d0,d4 move.w d4,(a1)+ addq.b #1,d2 addq.b #1,d3 dbf d1,Deform_LZ_2 rts

End of function Deform_LZ

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LZ_Wave_Data: dc.b 1, 1, 2, 2, 3, 3, 3, 3, 2, 2, 1, 1, 0, 0, 0, 0 dc.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 dc.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 dc.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 dc.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 dc.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 dc.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 dc.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 dc.b $FF,$FF,$FE,$FE,$FD,$FD,$FD,$FD,$FE,$FE,$FF,$FF, 0, 0, 0, 0 dc.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 dc.b 1, 1, 2, 2, 3, 3, 3, 3, 2, 2, 1, 1, 0, 0, 0, 0 dc.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 dc.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 dc.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 dc.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 dc.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

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Deform_MZ: move.w ($FFFFF73A).w,d4 ext.l d4 asl.l #6,d4 move.l d4,d1 asl.l #1,d4 add.l d1,d4 moveq #2,d6 bsr.w ScrollBlock4 move.w ($FFFFF73A).w,d4 ext.l d4 asl.l #6,d4 moveq #6,d6 bsr.w ScrollBlock6 move.w ($FFFFF73A).w,d4 ext.l d4 asl.l #7,d4 moveq #4,d6 bsr.w ScrollBlock5 move.w #$200,d0 move.w ($FFFFF704).w,d1 subi.w #$1C8,d1 bcs.s Deform_MZ_1 move.w d1,d2 add.w d1,d1 add.w d2,d1 asr.w #2,d1 add.w d1,d0

Deform_MZ_1: ; XREF: Deform_MZ move.w d0,($FFFFF714).w move.w d0,($FFFFF71C).w bsr.w ScrollBlock3 move.w ($FFFFF70C).w,($FFFFF618).w move.b ($FFFFF756).w,d0 or.b ($FFFFF758).w,d0 or.b d0,($FFFFF75A).w clr.b ($FFFFF756).w clr.b ($FFFFF758).w lea ($FFFFA800).w,a1 move.w ($FFFFF700).w,d2 neg.w d2 move.w d2,d0 asr.w #2,d0 sub.w d2,d0 ext.l d0 asl.l #3,d0 divs.w #5,d0 ext.l d0 asl.l #4,d0 asl.l #8,d0 moveq #0,d3 move.w d2,d3 asr.w #1,d3 move.w #4,d1

Deform_MZ_2: ; XREF: Deform_MZ move.w d3,(a1)+ swap d3 add.l d0,d3 swap d3 dbf d1,Deform_MZ_2 move.w ($FFFFF718).w,d0 neg.w d0 move.w #1,d1

Deform_MZ_3: ; XREF: Deform_MZ move.w d0,(a1)+ dbf d1,Deform_MZ_3 move.w ($FFFFF710).w,d0 neg.w d0 move.w #8,d1

Deform_MZ_4: ; XREF: Deform_MZ move.w d0,(a1)+ dbf d1,Deform_MZ_4 move.w ($FFFFF708).w,d0 neg.w d0 move.w #$F,d1

Deform_MZ_5: ; XREF: Deform_MZ move.w d0,(a1)+ dbf d1,Deform_MZ_5 lea ($FFFFA800).w,a2 move.w ($FFFFF70C).w,d0 subi.w #$200,d0 move.w d0,d2 cmpi.w #$100,d0 bcs.s Deform_MZ_6 move.w #$100,d0

Deform_MZ_6: ; XREF: Deform_MZ andi.w #$1F0,d0 lsr.w #3,d0 lea (a2,d0.w),a2 bra.w Deform_All

===========================================================================

Deform_SLZ: move.w ($FFFFF73C).w,d5 ext.l d5 asl.l #7,d5 bsr.w ScrollBlock2 move.w ($FFFFF70C).w,($FFFFF618).w lea ($FFFFA800).w,a1 move.w ($FFFFF700).w,d2 neg.w d2 move.w d2,d0 asr.w #3,d0 sub.w d2,d0 ext.l d0 asl.l #4,d0 divs.w #$1C,d0 ext.l d0 asl.l #4,d0 asl.l #8,d0 moveq #0,d3 move.w d2,d3 move.w #$1B,d1

Deform_SLZ_1: ; XREF: Deform_MZ move.w d3,(a1)+ swap d3 add.l d0,d3 swap d3 dbf d1,Deform_SLZ_1 move.w d2,d0 asr.w #3,d0 move.w d0,d1 asr.w #1,d1 add.w d1,d0 move.w #4,d1

Deform_SLZ_2: ; XREF: Deform_MZ move.w d0,(a1)+ dbf d1,Deform_SLZ_2 move.w d2,d0 asr.w #2,d0 move.w #4,d1

Deform_SLZ_3: ; XREF: Deform_MZ move.w d0,(a1)+ dbf d1,Deform_SLZ_3 move.w d2,d0 asr.w #1,d0 move.w #$1D,d1

Deform_SLZ_4: ; XREF: Deform_MZ move.w d0,(a1)+ dbf d1,Deform_SLZ_4 lea ($FFFFA800).w,a2 move.w ($FFFFF70C).w,d0 move.w d0,d2 subi.w #$C0,d0 ; 'À' andi.w #$3F0,d0 lsr.w #3,d0 lea (a2,d0.w),a2

Deform_All: ; XREF: Deform_MZ, Deform_SYZ, ... lea ($FFFFCC00).w,a1 move.w #$E,d1 move.w ($FFFFF700).w,d0 neg.w d0 swap d0 andi.w #$F,d2 add.w d2,d2 move.w (a2)+,d0 jmp Deform_All_2(pc,d2.w)

End of function Deform_MZ

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Deform_All_1: ; XREF: Deform_All move.w (a2)+,d0

Deform_All_2: move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ move.l d0,(a1)+ dbf d1,Deform_All_1 rts

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Deform_SYZ: move.w ($FFFFF73C).w,d5 ext.l d5 asl.l #4,d5 move.l d5,d1 asl.l #1,d5 add.l d1,d5 bsr.w ScrollBlock2 move.w ($FFFFF70C).w,($FFFFF618).w lea ($FFFFA800).w,a1 move.w ($FFFFF700).w,d2 neg.w d2 move.w d2,d0 asr.w #3,d0 sub.w d2,d0 ext.l d0 asl.l #3,d0 divs.w #8,d0 ext.l d0 asl.l #4,d0 asl.l #8,d0 moveq #0,d3 move.w d2,d3 asr.w #1,d3 move.w #7,d1

Deform_SYZ_1: ; XREF: Deform_SYZ move.w d3,(a1)+ swap d3 add.l d0,d3 swap d3 dbf d1,Deform_SYZ_1 move.w d2,d0 asr.w #3,d0 move.w #4,d1

Deform_SYZ_2: ; XREF: Deform_SYZ move.w d0,(a1)+ dbf d1,Deform_SYZ_2 move.w d2,d0 asr.w #2,d0 move.w #5,d1

Deform_SYZ_3: ; XREF: Deform_SYZ move.w d0,(a1)+ dbf d1,Deform_SYZ_3 move.w d2,d0 move.w d2,d1 asr.w #1,d1 sub.w d1,d0 ext.l d0 asl.l #4,d0 divs.w #$E,d0 ext.l d0 asl.l #4,d0 asl.l #8,d0 moveq #0,d3 move.w d2,d3 asr.w #1,d3 move.w #$D,d1

Deform_SYZ_4: ; XREF: Deform_SYZ move.w d3,(a1)+ swap d3 add.l d0,d3 swap d3 dbf d1,Deform_SYZ_4 lea ($FFFFA800).w,a2 move.w ($FFFFF70C).w,d0 move.w d0,d2 andi.w #$1F0,d0 lsr.w #3,d0 lea (a2,d0.w),a2 bra.w Deform_All

End of function Deform_SYZ

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Deform_SBZ: tst.b ($FFFFFE11).w bne.w Deform_SBZ_Act2 move.w ($FFFFF73A).w,d4 ext.l d4 asl.l #7,d4 moveq #2,d6 bsr.w ScrollBlock4 move.w ($FFFFF73A).w,d4 ext.l d4 asl.l #6,d4 moveq #6,d6 bsr.w ScrollBlock6 move.w ($FFFFF73A).w,d4 ext.l d4 asl.l #5,d4 move.l d4,d1 asl.l #1,d4 add.l d1,d4 moveq #4,d6 bsr.w ScrollBlock5 moveq #0,d4 move.w ($FFFFF73C).w,d5 ext.l d5 asl.l #5,d5 bsr.w ScrollBlock1_2 move.w ($FFFFF70C).w,d0 move.w d0,($FFFFF714).w move.w d0,($FFFFF71C).w move.w d0,($FFFFF618).w move.b ($FFFFF756).w,d0 or.b ($FFFFF75A).w,d0 or.b d0,($FFFFF758).w clr.b ($FFFFF756).w clr.b ($FFFFF75A).w lea ($FFFFA800).w,a1 move.w ($FFFFF700).w,d2 neg.w d2 asr.w #2,d2 move.w d2,d0 asr.w #1,d0 sub.w d2,d0 ext.l d0 asl.l #3,d0 divs.w #4,d0 ext.l d0 asl.l #4,d0 asl.l #8,d0 moveq #0,d3 move.w d2,d3 move.w #3,d1

Deform_SBZ_1: ; XREF: Deform_SBZ move.w d3,(a1)+ swap d3 add.l d0,d3 swap d3 dbf d1,Deform_SBZ_1 move.w ($FFFFF718).w,d0 neg.w d0 move.w #9,d1

Deform_SBZ_2: ; XREF: Deform_SBZ move.w d0,(a1)+ dbf d1,Deform_SBZ_2 move.w ($FFFFF710).w,d0 neg.w d0 move.w #6,d1

Deform_SBZ_3: ; XREF: Deform_SBZ move.w d0,(a1)+ dbf d1,Deform_SBZ_3 move.w ($FFFFF708).w,d0 neg.w d0 move.w #$A,d1

Deform_SBZ_4: ; XREF: Deform_SBZ move.w d0,(a1)+ dbf d1,Deform_SBZ_4 lea ($FFFFA800).w,a2 move.w ($FFFFF70C).w,d0 move.w d0,d2 andi.w #$1F0,d0 lsr.w #3,d0 lea (a2,d0.w),a2 bra.w Deform_All

===========================================================================

Deform_SBZ_Act2: ; XREF: Deform_SBZ move.w ($FFFFF73A).w,d4 ext.l d4 asl.l #6,d4 move.w ($FFFFF73C).w,d5 ext.l d5 asl.l #5,d5 bsr.w ScrollBlock1 move.w ($FFFFF70C).w,($FFFFF618).w lea ($FFFFCC00).w,a1 move.w #$DF,d1 ; 'ß' move.w ($FFFFF700).w,d0 neg.w d0 swap d0 move.w ($FFFFF708).w,d0 neg.w d0

Deform_SBZ_Act2_1: ; XREF: Deform_SBZ move.l d0,(a1)+ dbf d1,Deform_SBZ_Act2_1 rts

End of function Deform_SBZ</asm>

Step 4

The new Bg drawing system required a different method of scrolling the BGs themselves. Go to ScrollBlock1 and replace everything from there until the end of ScrollBlock4 with the following: <asm>ScrollBlock1: ; XREF: Deform_LZ, Deform_SBZ move.l ($FFFFF708).w,d2 move.l d2,d0 add.l d4,d0 move.l d0,($FFFFF708).w move.l d0,d1 swap d1 andi.w #$10,d1 move.b ($FFFFF74C).w,d3 eor.b d3,d1 bne.s ScrollBlock1_2 eori.b #$10,($FFFFF74C).w sub.l d2,d0 bpl.s ScrollBlock1_1 bset #2,($FFFFF756).w bra.s ScrollBlock1_2

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ScrollBlock1_1: ; XREF: ScrollBlock1 bset #3,($FFFFF756).w

ScrollBlock1_2: ; XREF: ScrollBlock1, Deform_SBZ, ... move.l ($FFFFF70C).w,d3 move.l d3,d0 add.l d5,d0 move.l d0,($FFFFF70C).w move.l d0,d1 swap d1 andi.w #$10,d1 move.b ($FFFFF74D).w,d2 eor.b d2,d1 bne.s ScrollBlock1_End eori.b #$10,($FFFFF74D).w sub.l d3,d0 bpl.s ScrollBlock1_3 bset #0,($FFFFF756).w rts

===========================================================================

ScrollBlock1_3: ; XREF: ScrollBlock1 bset #1,($FFFFF756).w

ScrollBlock1_End: ; XREF: ScrollBlock1 rts

End of function ScrollBlock1

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ScrollBlock2: ; XREF: Deform_MZ, Deform_SYZ move.l ($FFFFF70C).w,d3 move.l d3,d0 add.l d5,d0 move.l d0,($FFFFF70C).w move.l d0,d1 swap d1 andi.w #$10,d1 move.b ($FFFFF74D).w,d2 eor.b d2,d1 bne.s ScrollBlock2_End eori.b #$10,($FFFFF74D).w sub.l d3,d0 bpl.s ScrollBlock2_1 bset #4,($FFFFF756).w rts

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ScrollBlock2_1: ; XREF: ScrollBlock2 bset #5,($FFFFF756).w

ScrollBlock2_End: ; XREF: ScrollBlock2 rts

End of function ScrollBlock2

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ScrollBlock3: ; XREF: Deform_MZ move.w ($FFFFF70C).w,d3 move.w d0,($FFFFF70C).w move.w d0,d1 andi.w #$10,d1 move.b ($FFFFF74D).w,d2 eor.b d2,d1 bne.s ScrollBlock3_End eori.b #$10,($FFFFF74D).w sub.w d3,d0 bpl.s ScrollBlock3_1 bset #0,($FFFFF756).w rts

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ScrollBlock3_1: ; XREF: ScrollBlock3 bset #1,($FFFFF756).w

ScrollBlock3_End: ; XREF: ScrollBlock3 rts

End of function ScrollBlock3

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

ScrollBlock4: ; XREF: Deform_MZ, Deform_SBZ move.l ($FFFFF708).w,d2 move.l d2,d0 add.l d4,d0 move.l d0,($FFFFF708).w move.l d0,d1 swap d1 andi.w #$10,d1 move.b ($FFFFF74C).w,d3 eor.b d3,d1 bne.s ScrollBlock4_End eori.b #$10,($FFFFF74C).w sub.l d2,d0 bpl.s ScrollBlock4_1 bset d6,($FFFFF756).w bra.s ScrollBlock4_End

===========================================================================

ScrollBlock4_1: ; XREF: ScrollBlock4 addq.b #1,d6 bset d6,($FFFFF756).w

ScrollBlock4_End: ; XREF: ScrollBlock4 rts

End of function ScrollBlock4

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

ScrollBlock5: ; XREF: Deform_GHZ, Deform_MZ, ... move.l ($FFFFF710).w,d2 move.l d2,d0 add.l d4,d0 move.l d0,($FFFFF710).w move.l d0,d1 swap d1 andi.w #$10,d1 move.b ($FFFFF74E).w,d3 eor.b d3,d1 bne.s ScrollBlock5_End eori.b #$10,($FFFFF74E).w sub.l d2,d0 bpl.s ScrollBlock5_1 bset d6,($FFFFF758).w bra.s ScrollBlock5_End

===========================================================================

ScrollBlock5_1: ; XREF: ScrollBlock5 addq.b #1,d6 bset d6,($FFFFF758).w

ScrollBlock5_End: ; XREF: ScrollBlock5 rts

End of function ScrollBlock5

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

ScrollBlock6: ; XREF: Deform_GHZ, Deform_MZ, ... move.l ($FFFFF718).w,d2 move.l d2,d0 add.l d4,d0 move.l d0,($FFFFF718).w move.l d0,d1 swap d1 andi.w #$10,d1 move.b ($FFFFF750).w,d3 eor.b d3,d1 bne.s ScrollBlock6_End eori.b #$10,($FFFFF750).w sub.l d2,d0 bpl.s ScrollBlock6_1 bset d6,($FFFFF75A).w bra.s ScrollBlock6_End

===========================================================================

ScrollBlock6_1: ; XREF: ScrollBlock6 addq.b #1,d6 bset d6,($FFFFF75A).w

ScrollBlock6_End: ; XREF: ScrollBlock6 rts

End of function ScrollBlock6</asm>

Don't worry that there are six BGScroll functions now, that's taken cared of.

Step 5

Finally, the biggest part: the BG drawing code. Go to sub_6886 and replace everything from there until the end of LoadTilesFromStart2 (that's a VERY long way, up until MainLoadBlockLoad) with the following: <asm>sub_6886: lea ($C00004).l,a5 lea ($C00000).l,a6 lea ($FFFFF756).w,a2 lea ($FFFFF708).w,a3 lea ($FFFFA440).w,a4 move.w #$6000,d2 bsr.w sub_6D0A lea ($FFFFF758).w,a2 lea ($FFFFF710).w,a3 bra.w sub_6DA6

End of function sub_6886

---------------------------------------------------------------------------

Subroutine to display correct tiles as you move

---------------------------------------------------------------------------

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

LoadTilesAsYouMove: ; XREF: Demo_Time lea ($C00004).l,a5 lea ($C00000).l,a6 lea ($FFFFFF32).w,a2 lea ($FFFFFF18).w,a3 lea ($FFFFA440).w,a4 move.w #$6000,d2 bsr.w sub_6D0A lea ($FFFFFF34).w,a2 lea ($FFFFFF20).w,a3 bsr.w sub_6DA6 lea ($FFFFFF36).w,a2 lea ($FFFFFF28).w,a3 bsr.w sub_6EA4 lea ($FFFFFF30).w,a2 lea ($FFFFFF10).w,a3 lea ($FFFFA400).w,a4 move.w #$4000,d2 tst.b ($FFFFF745).w beq.s Draw_FG move.b #0,($FFFFF745).w ;Reset the redraw flag moveq #-$10,d4 ;Go to top line oflevel data relative camera position moveq #$F,d6 ;

Draw_All: movem.l d4-d6,-(sp) ; This whole routine basically redraws the whole moveq #-$10,d5 ; area instead of merely a line of tiles move.w d4,d1 bsr.w Calc_VRAM_Pos move.w d1,d4 moveq #-$10,d5 bsr.w DrawTiles_LR movem.l (sp)+,d4-d6 addi.w #$10,d4 dbf d6,Draw_All rts

Draw_FG: tst.b (a2) beq.s locret_6D08 bclr #0,(a2) beq.s loc_6CBE moveq #-$10,d4 moveq #-$10,d5 bsr.w Calc_VRAM_Pos moveq #-$10,d4 moveq #-$10,d5 bsr.w DrawTiles_LR

loc_6CBE: bclr #1,(a2) beq.s loc_6CD8 move.w #$E0,d4 ; 'à' moveq #-$10,d5 bsr.w Calc_VRAM_Pos move.w #$E0,d4 ; 'à' moveq #-$10,d5 bsr.w DrawTiles_LR

loc_6CD8: bclr #2,(a2) beq.s loc_6CEE moveq #-$10,d4 moveq #-$10,d5 bsr.w Calc_VRAM_Pos moveq #-$10,d4 moveq #-$10,d5 bsr.w DrawTiles_TB

loc_6CEE: bclr #3,(a2) beq.s locret_6D08 moveq #-$10,d4 move.w #$140,d5 bsr.w Calc_VRAM_Pos moveq #-$10,d4 move.w #$140,d5 bsr.w DrawTiles_TB

locret_6D08: rts

End of function LoadTilesAsYouMove

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

sub_6D0A: tst.b (a2) beq.w locret_6DA4 bclr #0,(a2) beq.s loc_6D26 moveq #-$10,d4 moveq #-$10,d5 bsr.w Calc_VRAM_Pos moveq #-$10,d4 moveq #-$10,d5 bsr.w DrawTiles_LR

loc_6D26: bclr #1,(a2) beq.s loc_6D40 move.w #$E0,d4 ; 'à' moveq #-$10,d5 bsr.w Calc_VRAM_Pos move.w #$E0,d4 ; 'à' moveq #-$10,d5 bsr.w DrawTiles_LR

loc_6D40: bclr #2,(a2) beq.s loc_6D56 moveq #-$10,d4 moveq #-$10,d5 bsr.w Calc_VRAM_Pos moveq #-$10,d4 moveq #-$10,d5 bsr.w DrawTiles_TB

loc_6D56: bclr #3,(a2) beq.s loc_6D70 moveq #-$10,d4 move.w #$140,d5 bsr.w Calc_VRAM_Pos moveq #-$10,d4 move.w #$140,d5 bsr.w DrawTiles_TB

loc_6D70: bclr #4,(a2) beq.s loc_6D88 moveq #-$10,d4 moveq #0,d5 bsr.w loc_7176 moveq #-$10,d4 moveq #0,d5 moveq #$1F,d6 bsr.w DrawTiles_LR3

loc_6D88: bclr #5,(a2) beq.s locret_6DA4 move.w #$E0,d4 ; 'à' moveq #0,d5 bsr.w loc_7176 move.w #$E0,d4 ; 'à' moveq #0,d5 moveq #$1F,d6 bsr.w DrawTiles_LR3

locret_6DA4: rts

End of function sub_6D0A

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

sub_6DA6: tst.b (a2) beq.w locret_6DF2 cmpi.b #5,($FFFFFE10).w beq.w loc_6E16 bclr #0,(a2) beq.s loc_6DD2 move.w #$70,d4 ; 'p' moveq #-$10,d5 bsr.w Calc_VRAM_Pos move.w #$70,d4 ; 'p' moveq #-$10,d5 moveq #2,d6 bsr.w DrawTiles_TB2

loc_6DD2: bclr #1,(a2) beq.s locret_6DF2 move.w #$70,d4 ; 'p' move.w #$140,d5 bsr.w Calc_VRAM_Pos move.w #$70,d4 ; 'p' move.w #$140,d5 moveq #2,d6 bsr.w DrawTiles_TB2

locret_6DF2: rts

===========================================================================

unk_6DF4: dc.b 0 ; unk_6DF5: dc.b 0 ; dc.b 0 ; dc.b 0 ; dc.b 0 ; dc.b 6 ; dc.b 6 ; dc.b 6 ; dc.b 6 ; dc.b 6 ; dc.b 6 ; dc.b 6 ; dc.b 6 ; dc.b 6 ; dc.b 6 ; dc.b 4 ; dc.b 4 ; dc.b 4 ; dc.b 4 ; dc.b 4 ; dc.b 4 ; dc.b 4 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 0 ;

===========================================================================

loc_6E16: moveq #-$10,d4 bclr #0,(a2) bne.s loc_6E28 bclr #1,(a2) beq.s loc_6E72 move.w #$E0,d4 ; 'à'

loc_6E28: lea (unk_6DF5).l,a0 move.w ($FFFFF70C).w,d0 add.w d4,d0 andi.w #$1F0,d0 lsr.w #4,d0 move.b (a0,d0.w),d0 lea (unk_6FE4).l,a3 movea.w (a3,d0.w),a3 beq.s loc_6E5E moveq #-$10,d5 movem.l d4-d5,-(sp) bsr.w Calc_VRAM_Pos movem.l (sp)+,d4-d5 bsr.w DrawTiles_LR bra.s loc_6E72

===========================================================================

loc_6E5E: moveq #0,d5 movem.l d4-d5,-(sp) bsr.w loc_7176 movem.l (sp)+,d4-d5 moveq #$1F,d6 bsr.w DrawTiles_LR3

loc_6E72: tst.b (a2) bne.s loc_6E78 rts

===========================================================================

loc_6E78: moveq #-$10,d4 moveq #-$10,d5 move.b (a2),d0 andi.b #-$58,d0 beq.s loc_6E8C lsr.b #1,d0 move.b d0,(a2) move.w #$140,d5

loc_6E8C: lea (unk_6DF4).l,a0 move.w ($FFFFF70C).w,d0 andi.w #$1F0,d0 lsr.w #4,d0 lea (a0,d0.w),a0 bra.w loc_6FEC

End of function sub_6DA6

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

sub_6EA4: tst.b (a2) beq.w locret_6EF0 cmpi.b #2,($FFFFFE10).w beq.w loc_6F54 bclr #0,(a2) beq.s loc_6ED0_2 move.w #$40,d4 ; '@' moveq #-$10,d5 bsr.w Calc_VRAM_Pos move.w #$40,d4 ; '@' moveq #-$10,d5 moveq #2,d6 bsr.w DrawTiles_TB2

loc_6ED0_2: bclr #1,(a2) beq.s locret_6EF0 move.w #$40,d4 ; '@' move.w #$140,d5 bsr.w Calc_VRAM_Pos move.w #$40,d4 ; '@' move.w #$140,d5 moveq #2,d6 bsr.w DrawTiles_TB2

locret_6EF0: rts

===========================================================================

unk_6EF2: dc.b 0 ; unk_6EF3: dc.b 0 ; dc.b 0 ; dc.b 0 ; dc.b 0 ; dc.b 0 ; dc.b 6 ; dc.b 6 ; dc.b 4 ; dc.b 4 ; dc.b 4 ; dc.b 4 ; dc.b 4 ; dc.b 4 ; dc.b 4 ; dc.b 4 ; dc.b 4 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 2 ; dc.b 0 ;

===========================================================================

loc_6F54: moveq #-$10,d4 bclr #0,(a2) bne.s loc_6F66 bclr #1,(a2) beq.s loc_6FAE move.w #$E0,d4 ; 'à'

loc_6F66: lea (unk_6EF3).l,a0 move.w ($FFFFF70C).w,d0 subi.w #$200,d0 add.w d4,d0 andi.w #$7F0,d0 lsr.w #4,d0 move.b (a0,d0.w),d0 movea.w unk_6FE4(pc,d0.w),a3 beq.s loc_6F9A moveq #-$10,d5 movem.l d4-d5,-(sp) bsr.w Calc_VRAM_Pos movem.l (sp)+,d4-d5 bsr.w DrawTiles_LR bra.s loc_6FAE

===========================================================================

loc_6F9A: moveq #0,d5 movem.l d4-d5,-(sp) bsr.w loc_7176 movem.l (sp)+,d4-d5 moveq #$1F,d6 bsr.w DrawTiles_LR3

loc_6FAE: tst.b (a2) bne.s loc_6FB4 rts

===========================================================================

loc_6FB4: moveq #-$10,d4 moveq #-$10,d5 move.b (a2),d0 andi.b #-$58,d0 beq.s loc_6FC8 lsr.b #1,d0 move.b d0,(a2) move.w #$140,d5

loc_6FC8: lea (unk_6EF2).l,a0 move.w ($FFFFF70C).w,d0 subi.w #$200,d0 andi.w #$7F0,d0 lsr.w #4,d0 lea (a0,d0.w),a0 bra.w loc_6FEC

===========================================================================

unk_6FE4: dc.b $FF ; dc.b $18 ; dc.b $FF ; dc.b $18 ; dc.b $FF ; dc.b $20 ; dc.b $FF ; dc.b $28 ; (

===========================================================================

loc_6FEC: moveq #$F,d6 move.l #$800000,d7

loc_6FF4: moveq #0,d0 move.b (a0)+,d0 btst d0,(a2) beq.s loc_701C movea.w unk_6FE4(pc,d0.w),a3 movem.l d4-d5/a0,-(sp) movem.l d4-d5,-(sp) bsr.w sub_712A movem.l (sp)+,d4-d5 bsr.w Calc_VRAM_Pos bsr.w sub_70AC movem.l (sp)+,d4-d5/a0

loc_701C: addi.w #$10,d4 dbf d6,loc_6FF4 clr.b (a2) rts

End of function sub_6EA4

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

DrawTiles_LR: moveq #$15,d6

End of function DrawTiles_LR

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

DrawTiles_LR2: move.l #$800000,d7 move.l d0,d1

loc_7032: movem.l d4-d5,-(sp) bsr.w sub_712A move.l d1,d0 bsr.w sub_70AC addq.b #4,d1 andi.b #$7F,d1 ; '?' movem.l (sp)+,d4-d5 addi.w #$10,d5 dbf d6,loc_7032 rts

End of function DrawTiles_LR2

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

DrawTiles_LR3: move.l #$800000,d7 move.l d0,d1

loc_705C: movem.l d4-d5,-(sp) bsr.w loc_712C move.l d1,d0 bsr.w sub_70AC addq.b #4,d1 andi.b #$7F,d1 ; '?' movem.l (sp)+,d4-d5 addi.w #$10,d5 dbf d6,loc_705C rts

End of function DrawTiles_LR3

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

DrawTiles_TB: moveq #$F,d6

End of function DrawTiles_TB

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

DrawTiles_TB2: move.l #$800000,d7 move.l d0,d1

loc_7088: movem.l d4-d5,-(sp) bsr.w sub_712A move.l d1,d0 bsr.w sub_70AC addi.w #$100,d1 andi.w #$FFF,d1 movem.l (sp)+,d4-d5 addi.w #$10,d4 dbf d6,loc_7088 rts

End of function DrawTiles_TB2

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

sub_70AC: or.w d2,d0 swap d0 btst #4,(a0) bne.s loc_70E8 btst #3,(a0) bne.s loc_70C8 move.l d0,(a5) move.l (a1)+,(a6) add.l d7,d0 move.l d0,(a5) move.l (a1)+,(a6) rts

===========================================================================

loc_70C8: move.l d0,(a5) move.l (a1)+,d4 eori.l #$8000800,d4 swap d4 move.l d4,(a6) add.l d7,d0 move.l d0,(a5) move.l (a1)+,d4 eori.l #$8000800,d4 swap d4 move.l d4,(a6) rts

===========================================================================

loc_70E8: btst #3,(a0) bne.s loc_710A move.l d0,(a5) move.l (a1)+,d5 move.l (a1)+,d4 eori.l #$10001000,d4 move.l d4,(a6) add.l d7,d0 move.l d0,(a5) eori.l #$10001000,d5 move.l d5,(a6) rts

===========================================================================

loc_710A: move.l d0,(a5) move.l (a1)+,d5 move.l (a1)+,d4 eori.l #$18001800,d4 swap d4 move.l d4,(a6) add.l d7,d0 move.l d0,(a5) eori.l #$18001800,d5 swap d5 move.l d5,(a6) rts

End of function sub_70AC

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

sub_712A: add.w (a3),d5

loc_712C: add.w 4(a3),d4 lea ($FFFFB000).w,a1 move.w d4,d3 lsr.w #1,d3 andi.w #$380,d3 lsr.w #3,d5 move.w d5,d0 lsr.w #5,d0 andi.w #$7F,d0 ; '?' add.w d3,d0 moveq #-1,d3 move.b (a4,d0.w),d3 beq.s locret_7172 subq.b #1,d3 andi.w #$7F,d3 ; '?' ror.w #7,d3 add.w d4,d4 andi.w #$1E0,d4 andi.w #$1E,d5 add.w d4,d3 add.w d5,d3 movea.l d3,a0 move.w (a0),d3 andi.w #$3FF,d3 lsl.w #3,d3 adda.w d3,a1

locret_7172: rts

End of function sub_712A

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

Calc_VRAM_Pos: add.w (a3),d5

loc_7176: add.w 4(a3),d4 andi.w #$F0,d4 ; 'ð' andi.w #$1F0,d5 lsl.w #4,d4 lsr.w #2,d5 add.w d5,d4 moveq #3,d0 swap d0 move.w d4,d0 rts

End of function Calc_VRAM_Pos

===========================================================================

add.w 4(a3),d4 add.w (a3),d5 andi.w #$F0,d4 ; 'ð' andi.w #$1F0,d5 lsl.w #4,d4 lsr.w #2,d5 add.w d5,d4 moveq #2,d0 swap d0 move.w d4,d0 rts

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

LoadTilesFromStart: lea ($C00004).l,a5 lea ($C00000).l,a6 lea ($FFFFF700).w,a3 lea ($FFFFA400).w,a4 move.w #$4000,d2 bsr.s LoadTilesFromStart2 lea ($FFFFF708).w,a3 lea ($FFFFA440).w,a4 move.w #$6000,d2 tst.b ($FFFFFE10).w beq.w loc_7220 cmpi.b #2,($FFFFFE10).w beq.w loc_725A cmpi.w #$500,($FFFFFE10).w beq.w loc_7288 cmpi.b #6,($FFFFFE10).w beq.w loc_7220

End of function LoadTilesFromStart

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

LoadTilesFromStart2: moveq #-$10,d4 moveq #$F,d6

loc_71FC: movem.l d4-d6,-(sp) moveq #0,d5 move.w d4,d1 bsr.w Calc_VRAM_Pos move.w d1,d4 moveq #0,d5 moveq #$1F,d6 bsr.w DrawTiles_LR2 movem.l (sp)+,d4-d6 addi.w #$10,d4 dbf d6,loc_71FC rts

End of function LoadTilesFromStart2

===========================================================================

loc_7220: moveq #0,d4 moveq #$F,d6

loc_7224: movem.l d4-d6,-(sp) lea (unk_724A).l,a0 move.w ($FFFFF70C).w,d0 add.w d4,d0 andi.w #$F0,d0 ; 'ð' bsr.w sub_72BA movem.l (sp)+,d4-d6 addi.w #$10,d4 dbf d6,loc_7224 rts

===========================================================================

unk_724A: dc.b 0 ; dc.b 0 ; dc.b 0 ; dc.b 0 ; dc.b 6 ; dc.b 6 ; dc.b 6 ; dc.b 4 ; dc.b 4 ; dc.b 4 ; dc.b 0 ; dc.b 0 ; dc.b 0 ; dc.b 0 ; dc.b 0 ; dc.b 0 ;

===========================================================================

loc_725A: moveq #-$10,d4 moveq #$F,d6

loc_725E: movem.l d4-d6,-(sp) lea (unk_6EF3).l,a0 move.w ($FFFFF70C).w,d0 subi.w #$200,d0 add.w d4,d0 andi.w #$7F0,d0 bsr.w sub_72BA movem.l (sp)+,d4-d6 addi.w #$10,d4 dbf d6,loc_725E rts

===========================================================================

loc_7288: moveq #-$10,d4 moveq #$F,d6

loc_728C: movem.l d4-d6,-(sp) lea (unk_6DF5).l,a0 move.w ($FFFFF70C).w,d0 add.w d4,d0 andi.w #$1F0,d0 bsr.w sub_72BA movem.l (sp)+,d4-d6 addi.w #$10,d4 dbf d6,loc_728C rts

===========================================================================

unk_72B2: dc.b $F7 ; ÷ dc.b 8 ; dc.b $F7 ; ÷ dc.b 8 ; dc.b $F7 ; ÷ dc.b $10 ; dc.b $F7 ; ÷ dc.b $18 ;

||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||

sub_72BA: lsr.w #4,d0 move.b (a0,d0.w),d0 movea.w unk_72B2(pc,d0.w),a3 beq.s loc_72DA moveq #-$10,d5 movem.l d4-d5,-(sp) bsr.w Calc_VRAM_Pos movem.l (sp)+,d4-d5 bsr.w DrawTiles_LR bra.s locret_72EE

===========================================================================

loc_72DA: moveq #0,d5 movem.l d4-d5,-(sp) bsr.w loc_7176 movem.l (sp)+,d4-d5 moveq #$1F,d6 bsr.w DrawTiles_LR3

locret_72EE: rts

End of function sub_72BA</asm>

Step 6

Assuming you haven't changed the backgrounds of your levels, compile it and give it a go!

Credits

• Hivebrain - for attempting this first
• Tweaker - for his assistance when I had some issues to resolve.