222 lines
5.8 KiB
NASM
222 lines
5.8 KiB
NASM
AdjustTransition:
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{
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lda $ab : and #$01ff : beq .reset
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phy : ldy #$06 ; operating on vertical registers during horizontal trans
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cpx.b #$02 : bcs .horizontalScrolling
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ldy #$00 ; operate on horizontal regs during vert trans
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.horizontalScrolling
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cmp #$0008 : bcs +
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pha : lda $ab : and #$0200 : beq ++
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pla : bra .add
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++ pla : eor #$ffff : inc ; convert to negative
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.add jsr AdjustCamAdd : ply : bra .reset
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+ lda $ab : and #$0200 : xba : tax
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lda.l OffsetTable,x : jsr AdjustCamAdd
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lda $ab : !sub #$0008 : sta $ab
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ply : bra .done
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.reset ; clear the $ab variable so to not disturb intra-tile doors
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stz $ab
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.done
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lda $00 : and #$01fc
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rtl
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}
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AdjustCamAdd:
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!add $00E2,y : pha
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and #$01ff : cmp #$0111 : !blt +
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cmp #$01f8 : !bge ++
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pla : and #$ff10 : pha : bra +
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++ pla : and #$ff00 : !add #$0100 : pha
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+ pla : sta $00E2,y : sta $00E0,y : rts
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; expects target quad in $05 (either 0 or 1) and target pixel in $04, target room should be in $a0
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; $06 is either $ff or $01/02
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; uses $00-$03 and $0e for calculation
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; also set up $ac
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ScrollY: ;change the Y offset variables
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lda $a0 : and.b #$f0 : lsr #3 : sta $0603 : inc : sta $0607
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lda $05 : bne +
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lda $603 : sta $00 : stz $01 : bra ++
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+ lda $607 : sta $00 : lda #$02 : sta $01
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++ ; $01 now contains 0 or 2 and $00 contains the correct lat
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stz $0e
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rep #$30
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lda $00 : pha
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lda $e8 : and #$01ff : sta $02
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lda $04 : jsr LimitYCamera : sta $00
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jsr CheckRoomLayoutY : bcc +
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lda $00 : cmp #$0080 : !bge ++
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cmp #$0010 : !blt .cmpSrll
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lda #$0010 : bra .cmpSrll
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++ cmp #$0100 : !bge .cmpSrll
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lda #$0100
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.cmpSrll sta $00
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; figures out scroll amt
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+ lda $00 : cmp $02 : bne +
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lda #$0000 : bra .next
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+ !blt +
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!sub $02 : inc $0e : bra .next
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+ lda $02 : !sub $00
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.next
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sta $ab
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jsr AdjustCameraBoundsY
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pla : sta $00
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sep #$30
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lda $04 : sta $20
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lda $00 : sta $21 : sta $0601 : sta $0605
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lda $01 : sta $aa
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lda $0e : asl : ora $ac : sta $ac
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lda $e9 : and #$01 : asl #2 : tax : lda $0603, x : sta $e9
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rts
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LimitYCamera:
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cmp #$006c : !bge +
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lda #$0000 : bra .end
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+ cmp #$017d : !blt +
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lda #$0110 : bra .end
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+ !sub #$006c
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.end rts
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CheckRoomLayoutY:
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jsr LoadRoomLayout ;switches to 8-bit
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cmp #$00 : beq .lock
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cmp #$07 : beq .free
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cmp #$01 : beq .free
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cmp #$04 : !bge .lock
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cmp #$02 : bne +
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lda $06 : cmp #$ff : beq .lock
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+ cmp #$03 : bne .free
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lda $06 : cmp #$ff : bne .lock
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.free rep #$30 : clc : rts
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.lock rep #$30 : sec : rts
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AdjustCameraBoundsY:
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jsr CheckRoomLayoutY : bcc .free
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; layouts that are camera locked (quads only)
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lda $04 : and #$00ff : cmp #$007d : !blt +
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lda #$0088 : bra ++
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+ cmp #$006d : !bge +
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lda #$0078 : bra ++
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+ !add #$000b
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; I think we no longer need the $02 variable
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++ sta $02 : lda $04 : and #$0100 : !add $02 : bra .setBounds
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; layouts where the camera is free
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.free lda $04 : cmp #$006c : !bge +
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lda #$0077 : bra .setBounds
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+ cmp #$017c : !blt +
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lda #$0187 : bra .setBounds
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+ !add #$000b
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.setBounds sta $0618 : inc #2 : sta $061a
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rts
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LoadRoomLayout:
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lda $a0 : asl : !add $a0 : tax
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lda $1f8001, x : sta $b8
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lda $1f8000, x : sta $b7
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sep #$30
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ldy #$01 : lda [$b7], y : and #$1c : lsr #2
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rts
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; expects target quad in $05 (either 0 or 1) and target pixel in $04, target room should be in $a0
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; uses $00-$03 and $0e for calculation
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; also set up $ac
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ScrollX: ;change the X offset variables
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lda $a0 : and.b #$0f : asl : sta $060b : inc : sta $060f
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lda $05 : bne +
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lda $60b : sta $00 : stz $01 : bra ++
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+ lda $60f : sta $00 : lda #$01 : sta $01
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++ ; $01 now contains 0 or 1 and $00 contains the correct long
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stz $0e ; pos/neg indicator
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rep #$30
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lda $00 : pha
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lda $e2 : and #$01ff : sta $02
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lda $04 : jsr LimitXCamera : sta $00
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jsr CheckRoomLayoutX : bcc +
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lda $00 : cmp #$0080 : !bge ++
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lda #$0000 : bra .cmpSrll
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++ lda #$0100
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.cmpSrll sta $00
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;figures out scroll amt
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+ lda $00 : cmp $02 : bne +
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lda #$0000 : bra .next
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+ !blt +
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!sub $02 : inc $0e : bra .next
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+ lda $02 : !sub $00
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.next
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sta $ab : lda $04
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cmp #$0078 : !bge +
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lda #$007f : bra ++
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+ cmp #$0178 : !blt +
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lda #$017f : bra ++
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+ !add #$0007
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++ sta $061c : inc #2 : sta $061e
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pla : sta $00
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sep #$30
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lda $04 : ldx $046d : bne .straight
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sta $22 : bra +
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.straight
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sta $046d ; set X position later
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+
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lda $00 : sta $23 : sta $0609 : sta $060d
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lda $01 : sta $a9
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lda $0e : asl : ora $ac : sta $ac
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lda $e3 : and #$01 : asl #2 : tax : lda $060b, x : sta $e3
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rts
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LimitXCamera:
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cmp #$0079 : !bge +
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lda #$0000 : bra .end
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+ cmp #$0178 : !blt +
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lda #$0178
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+ !sub #$0078
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.end rts
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CheckRoomLayoutX:
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jsr LoadRoomLayout ;switches to 8-bit
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cmp #$04 : !blt .lock
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cmp #$05 : bne +
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lda $06 : cmp #$ff : beq .lock
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+ cmp #$06 : bne .free
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lda $06 : cmp #$ff : bne .lock
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.free rep #$30 : clc : rts
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.lock rep #$30 : sec : rts
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ApplyScroll:
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rep #$30
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lda $ab : and #$01ff : sta $00
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lda $ab : and #$0200 : beq +
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lda $00e2, y : !add $00 : bra .end
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+ lda $00e2, y : !sub $00
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.end
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sta $00e2, y
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sta $00e0, y
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stz $ab : sep #$30 : rts
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QuadrantLoadOrderBeforeScroll:
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lda $045f : beq .end
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lda #$08 : sta $045c ; start with opposite quadrant row
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.end
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JML $0091c4 ; what we overwrote
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QuadrantLoadOrderAfterScroll:
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lda $045f : beq .end
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stz $045c : stz $045f ; draw other row and clear flag
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.end
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JML $0091c4 ; what we overwrote |