4cade/src/fx.lib.a

;license:MIT
;(c) 2024 by 4am
;
; common routines used by graphic effects
;
; Note: launcher code can call these routines directly. However,
; graphic effects are assembled as separate targets and must call
; these routines indirectly via the vectors defined in constants.a,
; e.g. iBuildHGRTables instead of BuildHGRTables.
;
; Public functions:
; - WaitForKeyWithTimeout
; - BuildHGRTables
; - BuildHGRMirrorTables
; - BuildHGRMirrorCols
; - BuildDHGRMirrorCols
; - BuildHGRDitherMasks
; - BuildDHGRDitherMasks

; - BuildHGRSparseBitmasks1Bit
; - BuildDHGRSparseBitmasks1Bit
; - ReverseCoordinates1Bit
; - RippleCoordinates1Bit
; - RippleCoordinates1Bit2
; - RippleCoordinates1Bit3
; - RippleCoordinates1Bit4
; - HGRPrecomputed1Bit
; - DHGRPrecomputed1Bit

; - BuildHGRSparseBitmasks2Bit
; - BuildDHGRSparseBitmasks2Bit
; - ReverseCoordinates2Bit
; - RippleCoordinates2Bit
; - HGRPrecomputed2Bit
; - DHGRPrecomputed2Bit

; - SetupPrecomputed3Bit
; - ReverseCoordinates3Bit
; - RippleCoordinates3Bit
; - HGRPrecomputed3Bit

         !source "src/fx/macros.hgr.a"
         !source "src/fx/macros.dhgr.a"
         !source "src/fx/macros.shr.a"
         !source "src/fx/macros.copybit.a"
         !source "src/fx/macros.misc.a"

WaitForKeyWithTimeout
; in:    A = timeout length (like standard $FCA8 wait routine)
; out:   A clobbered (not always 0 if key is pressed, but also not the key pressed)
;        X/Y preserved
         sec
@wait1   pha
@wait2   sbc   #1
         bne   @wait2
         pla
         bit   KBD
         bmi   @exit
         sbc   #1
         bne   @wait1
@exit    rts

; based on routine by John Brooks
; posted on comp.sys.apple2 on 2018-07-11
; https://groups.google.com/d/msg/comp.sys.apple2/v2HOfHOmeNQ/zD76fJg_BAAJ
BuildHGRTables
; out:   populates tables at $0201 (hgrlo) and $0301 (hgrhi)
;        A clobbered
;        X=$C0 (important! some callers rely on this)
;        Z=1
;        Y preserved
         ldx   #0
-        txa
         and   #$F8
         bpl   +
         ora   #5
+        asl
         bpl   +
         ora   #5
+        asl
         asl
         sta   hgrlo, x
         txa
         and   #7
         rol
         asl   hgrlo, x
         rol
         ora   #$20
         sta   hgrhi, x
         inx
         cpx   #$C0
         bne   -
         rts

BuildHGRMirrorTables
         ldx   #$C0
         ldy   #0
-        tya
         and   #$F8
         bpl   +
         ora   #5
+        asl
         bpl   +
         ora   #5
+        asl
         asl
         sta   hgrlomirror-1, x
         tya
         and   #7
         rol
         asl   hgrlomirror-1, x
         rol
         ora   #$20
         sta   hgr1himirror-1, x
         iny
         dex
         bne   -
         rts

BuildHGRMirrorCols
; in:    none
; out:   mirror_cols populated with lookup table to get $27-y for y in $00..$27
;        all registers and flags clobbered
         ldx   #$27
         ldy   #$00
-        tya
         sta   mirror_cols, x
         iny
         dex
         bpl   -
         rts

BuildDHGRMirrorCols
; out:   mirror_cols populated with lookup table to get $27-y for y in $00..$27
;        duplicated in both mainmem and auxmem
;        X=0
;        Z=1
         ldx   #$28
         ldy   #$00
-        tya
         sta   mirror_cols-1, x
         sta   $C005
         sta   mirror_cols-1, x
         sta   $C004
         iny
         dex
         bne   -
         rts

BuildHGRDitherMasks
         ldy   #40
-        lda   #%10110011
         sta   dithermasks, y
         lda   #%11100110
         sta   dithermasks+1, y
         lda   #%11001100
         sta   dithermasks+2, y
         lda   #%10011001
         sta   dithermasks+3, y
         dey
         dey
         dey
         dey
         bpl   -
         ldy   #43
         lda   #$FF
-        sta   no_masks, y
         dey
         bpl   -
         rts

BuildDHGRDitherMasks
         ldy   #40
-        lda   #%10011110
         sta   dithermasks, y
         lda   #%11111000
         sta   dithermasks+1, y
         lda   #%11100001
         sta   dithermasks+2, y
         lda   #%10000111
         sta   dithermasks+3, y
         dey
         dey
         dey
         dey
         bpl   -
         ldy   #43
-        lda   #$FF
         sta   no_masks, y
         dey
         bpl   -
         sta   $C005
         ldy   #40
-        lda   #%10001111
         sta   dithermasks, y
         lda   #%10111100
         sta   dithermasks+1, y
         lda   #%11110000
         sta   dithermasks+2, y
         lda   #%11000011
         sta   dithermasks+3, y
         dey
         dey
         dey
         dey
         bpl   -
         ldy   #43
-        lda   #$FF
         sta   no_masks, y
         dey
         bpl   -
         sta   $C004
         rts

BuildHGRSparseBitmasks1Bit
         lda   #%10000001
         sta   copymasks1bit
         sta   mirror_copymasks1bit+$C0

         lda   #%10000010
         sta   copymasks1bit+$20
         sta   mirror_copymasks1bit+$A0

         lda   #%10000100
         sta   copymasks1bit+$40
         sta   mirror_copymasks1bit+$80

         lda   #%10001000
         sta   copymasks1bit+$60
         sta   mirror_copymasks1bit+$60

         lda   #%10010000
         sta   copymasks1bit+$80
         sta   mirror_copymasks1bit+$40

         lda   #%10100000
         sta   copymasks1bit+$A0
         sta   mirror_copymasks1bit+$20

         lda   #%11000000
         sta   copymasks1bit+$C0
         sta   mirror_copymasks1bit
         rts

BuildDHGRSparseBitmasks1Bit
; out:   X=0
         ldx   #$00
         txa
-        sta   copymasks1bit, x
         sta   $C005
         sta   copymasks1bit, x
         sta   $C004
         inx
         bne   -
         ; X=0

         lda   #%00000111
         sta   copymasks1bit+$80
         sta   mirror_copymasks1bit+$40

         lda   #%00011000
         sta   copymasks1bit+$A0
         sta   mirror_copymasks1bit+$20

         lda   #%01100000
         sta   copymasks1bit+$C0
         sta   mirror_copymasks1bit

         sta   $C005

         lda   #%10000011
         sta   copymasks1bit
         sta   mirror_copymasks1bit+$C0

         lda   #%10001100
         sta   copymasks1bit+$20
         sta   mirror_copymasks1bit+$A0

         lda   #%10110000
         sta   copymasks1bit+$40
         sta   mirror_copymasks1bit+$80

         lda   #%11000000
         sta   copymasks1bit+$60
         sta   mirror_copymasks1bit+$60

         sta   $C004
         rts

ReverseCoordinates1Bit
         ldy   #0                    ; <Coordinates1Bit
         sty   $f0
         lda   #>Coordinates1Bit
         sta   $f1
         lda   #<(EndCoordinates1Bit - 2)
         sta   $f2
         lda   #>(EndCoordinates1Bit - 2)
         sta   $f3
         clc
         !byte $24
-        sec
--       lda   ($f0), y
         pha
         lda   ($f2), y
         sta   ($f0), y
         pla
         sta   ($f2), y
         iny
         bcc   -
         ldy   #0
         !byte $24
-        clc
         inc   $f0
         bne   +
         inc   $f1
+        lda   $f1
         eor   #>(Coordinates1Bit + $1A40)
         bne   +
         lda   $f0
         eor   #<(Coordinates1Bit + $1A40)
         beq   ++
+        lda   $f2
         bne   +
         dec   $f3
+        dec   $f2
         bcs   -
         bcc   --                    ; always
++       rts

!zone {
RippleCoordinates1Bit4
         lda   #<aslmod4
         +HIDE_NEXT_2_BYTES
RippleCoordinates1Bit3
         lda   #<aslmod3
         +HIDE_NEXT_2_BYTES
RippleCoordinates1Bit2
         lda   #<aslmod2
         +HIDE_NEXT_2_BYTES
RippleCoordinates1Bit
         lda   #<aslmod
         sta   @jsr+1
         lda   #2                    ; <(Coordinates1Bit + 2)
         sta   $f0
         ldy   #0
         sty   $f1
         lda   #$16                  ; <(Coordinates1Bit + 22)
         sta   $f2
         sty   $f3

         lda   #$1f
         sta   $ee
         lda   #$0d
         sta   $ef

         lda   Coordinates1Bit + 2
         sta   $e0
         lda   Coordinates1Bit + 3
         sta   $e1
         lda   Coordinates1Bit + 22
         sta   $e2
         lda   Coordinates1Bit + 23
         sta   $e3

---      ldx   #4
--       ldy   $ee, x
         lda   $ef, x
@jsr     jsr   aslmod                ; SMC on entry
         sty   $ee, x
         sta   $ef, x
         sty   $ec
         clc
         adc   #>Coordinates1Bit
         sta   $ed
         ldy   #0
         !byte $24
-        sec
         lda   ($ec), y
         pha
         lda   $de, x
         sta   ($ec), y
         pla
         sta   $de, x
         inx
         iny
         bcc   -
         dex
         dex
         dex
         dex
         bne   --
         dec   $ee
         bne   ---
         dec   $ef
         bpl   ---
         bmi   exit                 ; always branches
aslmod4  jsr   aslmod
aslmod3  jsr   aslmod
aslmod2  jsr   aslmod
aslmod   cmp   #$1A
!if (>aslmod != >aslmod4) {
         !serious "aslmod entry points are not on the same page"
}
         bcc   +
         bne   ++
         cpy   #$40
         bcc   +
++       iny
+        pha
         tya
         asl
         tay
         pla
         rol
         cmp   #$34
         bcc   exit
         bne   ++
         cpy   #$80
         bcc   exit
++       pha
         tya
         sbc   #$80
         tay
         pla
         sbc   #$34
exit     rts
}

!zone {
HGRPrecomputed1Bit
         jsr   BuildHGRTables
         jsr   BuildHGRMirrorTables
         jsr   BuildHGRMirrorCols
         jsr   BuildHGRSparseBitmasks1Bit
         +COPY_TO_0 .start, .end
         jmp   .InputLoop
.start
!pseudopc 0 {
.Exit1Bit rts
.InputLoop
         ldy   #0
.input=*+1
         ldx   Coordinates1Bit       ; first value: HGR row (only 0..95 will be in input array)
         bmi   .Exit1Bit             ; if > 127 then we're done
         +ROW_X_TO_BASE_ADDRESSES .src1, .src2, .dest1, .dest2
         +ROW_X_TO_MIRROR_ADDRESSES .mirror_src1, .mirror_src2, .mirror_dest1, .mirror_dest2

         inc   .input
         lda   (.input), y
         +HIGH_3_LOW_5 .input

         ; main 1x2 block in top-left quadrant
.src1=*+1
         lda   $FDFD, y
         eor   (<.dest1), y
         and   copymasks1bit, x
         eor   (<.dest1), y
.dest1=*+1
         sta   $FDFD, y
.src2=*+1
         lda   $FDFD, y
         eor   (<.dest2), y
         and   copymasks1bit, x
         eor   (<.dest2), y
.dest2=*+1
         sta   $FDFD, y

         ; corresponding 1x2 block in top-right quadrant (same row, opposite column)
         lda   mirror_cols, y
         tay
         +COPY_BIT .src1, .dest1, mirror_copymasks1bit
         +COPY_BIT .src2, .dest2, mirror_copymasks1bit

         ; corresponding 1x2 block in bottom-right quadrant (opposite row, opposite column)
.mirror_src1=*+1
         lda   $FDFD, y
         eor   (<.mirror_dest1), y
         and   mirror_copymasks1bit, x
         eor   (<.mirror_dest1), y
.mirror_dest1=*+1
         sta   $FDFD, y
.mirror_src2=*+1
         lda   $FDFD, y
         eor   (<.mirror_dest2), y
         and   mirror_copymasks1bit, x
         eor   (<.mirror_dest2), y
.mirror_dest2=*+1
         sta   $FDFD, y

         ; corresponding 1x2 block in bottom-left quadrant (opposite row, original column)
         lda   mirror_cols, y
         tay
         +COPY_BIT .mirror_src1, .mirror_dest1, copymasks1bit
         +COPY_BIT .mirror_src2, .mirror_dest2, copymasks1bit

         +INC_INPUT_AND_LOOP .input, .InputLoop
}
.end
}

!zone {
DHGRPrecomputed1Bit
         jsr   BuildDHGRSparseBitmasks1Bit
         jsr   BuildHGRTables
         jsr   BuildHGRMirrorTables
         jsr   BuildDHGRMirrorCols
         +COPY_TO_0 .start, .end
         jmp   .InputLoop
.start
!pseudopc 0 {
.Exit1Bit rts
.InputLoop
         ldy   #0
.input=*+1
         ldx   Coordinates1Bit       ; first value: HGR row (only 0..95 will be in input array)
         bmi   .Exit1Bit             ; if > 127 then we're done
         +ROW_X_TO_BASE_ADDRESSES .src1, .src2, .dest1, .dest2
         +ROW_X_TO_MIRROR_ADDRESSES .mirror_src1, .mirror_src2, .mirror_dest1, .mirror_dest2

         inc   .input
         lda   (.input), y
         +HIGH_3_LOW_5 .input
         sty   <.y
         clc
.bankloop
         lda   copymasks1bit, x
         beq   +
         sta   <.copymask

         ; main 1x2 block in top-left quadrant
.src1=*+1
         lda   $FDFD, y
         eor   (<.dest1), y
.copymask=*+1
         and   #$FD                  ; SMC
         eor   (<.dest1), y
.dest1=*+1
         sta   $FDFD, y
.src2=*+1
         lda   $FDFD, y
         eor   (<.dest2), y
         and   <.copymask
         eor   (<.dest2), y
.dest2=*+1
         sta   $FDFD, y

         ; corresponding 1x2 block in bottom-left quadrant (opposite row, original column)
         +COPY_BIT_ZP .mirror_src1, .mirror_dest1, .copymask
         +COPY_BIT_ZP .mirror_src2, .mirror_dest2, .copymask

+
         lda   mirror_copymasks1bit, x              ; exists at the same address in mainmem and auxmem but each is different
         beq   +
         sta   <.mirror_copymask
         ; corresponding 1x2 block in bottom-right quadrant (opposite row, opposite column)
         lda   mirror_cols, y                   ; duplicated in mainmem and auxmem
         tay
.mirror_src1=*+1
         lda   $FDFD, y
         eor   (<.mirror_dest1), y
.mirror_copymask=*+1
         and   #$FD                             ; SMC
         eor   (<.mirror_dest1), y
.mirror_dest1=*+1
         sta   $FDFD, y
.mirror_src2=*+1
         lda   $FDFD, y
         eor   (<.mirror_dest2), y
         and   <.mirror_copymask
         eor   (<.mirror_dest2), y
.mirror_dest2=*+1
         sta   $FDFD, y

         ; corresponding 1x2 block in top-right quadrant (same row, opposite column)
         +COPY_BIT_ZP .src1, .dest1, .mirror_copymask
         +COPY_BIT_ZP .src2, .dest2, .mirror_copymask
+
         bcs   +
         sta   $C003
         sta   $C005
.y=*+1
         ldy   #$FD
         sec
         bcs   .bankloop
+        sta   $C002
         sta   $C004

         +INC_INPUT_AND_LOOP .input, .InputLoop
}
.end
}

BuildHGRSparseBitmasks2Bit
         lda   #%10000011
         sta   copymasks2bit
         sta   mirror_copymasks2bit+$E0

         lda   #%10001100
         sta   copymasks2bit+$20
         sta   mirror_copymasks2bit+$C0

         lda   #%10110000
         sta   copymasks2bit+$40
         sta   mirror_copymasks2bit+$A0

         lda   #%11000000
         sta   copymasks2bit+$60
         sta   mirror_copymasks2bit+$80

         lda   #%10000001
         sta   copymasks2bit+$80
         sta   mirror_copymasks2bit+$60

         lda   #%10000110
         sta   copymasks2bit+$A0
         sta   mirror_copymasks2bit+$40

         lda   #%10011000
         sta   copymasks2bit+$C0
         sta   mirror_copymasks2bit+$20

         lda   #%11100000
         sta   copymasks2bit+$E0
         sta   mirror_copymasks2bit
         rts

BuildDHGRSparseBitmasks2Bit
         ldx   #$00
         txa
-        sta   copymasks2bit, x
         sta   $C005
         sta   copymasks2bit, x
         sta   $C004
         inx
         bne   -

         lda   #%10011111
         sta   copymasks2bit+$40
         sta   mirror_copymasks2bit+$A0

         lda   #%11100000
         sta   copymasks2bit+$60
         sta   mirror_copymasks2bit+$80

         lda   #%10000111
         sta   copymasks2bit+$C0
         sta   mirror_copymasks2bit+$20

         lda   #%11111000
         sta   copymasks2bit+$E0
         sta   mirror_copymasks2bit

         sta   $C005

         lda   #%10001111
         sta   copymasks2bit
         sta   mirror_copymasks2bit+$E0

         lda   #%11110000
         sta   copymasks2bit+$20
         sta   mirror_copymasks2bit+$C0

         lda   #%10000011
         sta   copymasks2bit+$80
         sta   mirror_copymasks2bit+$60

         lda   #%11111100
         sta   copymasks2bit+$A0
         sta   mirror_copymasks2bit+$40

         sta   $C004
         rts

ReverseCoordinates2Bit
         ldy   #0                    ; <Coordinates2Bit
         sty   $f0
         lda   #>Coordinates2Bit
         sta   $f1
         lda   #<(EndCoordinates2Bit - 2)
         sta   $f2
         lda   #>(EndCoordinates2Bit - 2)
         sta   $f3

         ldx   #$1E                  ; #$3C/2
         clc
         !byte $24
-        sec
--       lda   ($f0), y
         pha
         lda   ($f2), y
         sta   ($f0), y
         pla
         sta   ($f2), y
         iny
         bcc   -
         ldy   #0
         !byte $24
-        clc
         inc   $f0
         bne   +
         inc   $f1
         dex
         beq   ++
+        lda   $f2
         bne   +
         dec   $f3
+        dec   $f2
         bcs   -
         bcc   --                    ; always branches
++       rts

RippleCoordinates2Bit
         ldy   #0

         ldx   #$33
-        lda   @ptrtbl, x
         sta   $c0, x
         dex
         bpl   -

         lda   #$9b
         sta   $fe
         iny
         sty   $ff

         ldx   #6
-        lda   Coordinates2Bit + 1, x
         sta   $7f, x
         lda   Coordinates2Bit + 9, x
         sta   $85, x
         lda   Coordinates2Bit + 17, x
         sta   $8b, x
         lda   Coordinates2Bit + 65, x
         sta   $9b, x
         dex
         bne   -
         lda   Coordinates2Bit + 28
         sta   $92
         lda   Coordinates2Bit + 29
         sta   $93
         ldx   #4
-        lda   Coordinates2Bit + 33, x
         sta   $93, x
         lda   Coordinates2Bit + 41, x
         sta   $97, x
         lda   Coordinates2Bit + 83, x
         sta   $a1, x
         dex
         bne   -
         ldx   #2
-        lda   Coordinates2Bit + 125, x
         sta   $a5, x
         lda   Coordinates2Bit + 131, x
         sta   $a7, x
         lda   Coordinates2Bit + 139, x
         sta   $a9, x
         lda   Coordinates2Bit + 169, x
         sta   $ab, x
         lda   Coordinates2Bit + 237, x
         sta   $ad, x
         lda   Coordinates2Bit + 2193, x
         sta   $af, x
         lda   Coordinates2Bit + 6581, x
         sta   $b1, x
         dex
         bne   -

---      ldx   #$34
--       lda   $be, x
         tay
         ora   $bf, x
         beq   +
         lda   $bf, x
         jsr   @aslmod
         sty   $be, x
         sta   $bf, x
         sty   $fc
         clc
         adc   #>Coordinates2Bit
         sta   $fd
         ldy   #0
         !byte $24
-        sec
         lda   ($fc), y
         pha
         lda   $7e, x
         sta   ($fc), y
         pla
         sta   $7e, x
         inx
         iny
         bcc   -
         dex
         dex
+        dex
         dex
         bne   --
         ldy   #1
         lda   $fe
         eor   #<(411 - 2)
         beq   +
         ldy   #9
         eor   #<(411 - 2) xor <(411 - 136)
         bne   ++
+
-        ldx   @zerotbl, y
         sta   $0, x
         sta   $1, x
         dey
         bpl   -
++       dec   $fe
         bne   ---
         dec   $ff
         bpl   ---
         bmi   @exit                  ; always branches
@aslmod  jsr   +
+        cmp   #$1E
         bcc   +
         iny
+        pha
         tya
         asl
         tay
         pla
         rol
         cmp   #$3C
         bcc   @exit
         sbc   #$3C
@exit    rts
@ptrtbl  !word 2, 4, 6, 10, 12, 14, 18, 20
         !word 22, 28, 34, 36, 42, 44, 66, 68
         !word 70, 84, 86, 126, 132, 140, 170, 238
         !word 2194, 6582
@zerotbl !byte $f0, $f2, $ca, $d2, $d8, $e0, $e2, $e6, $ea, $ee

!zone {
HGRPrecomputed2Bit
         jsr   BuildHGRTables
         jsr   BuildHGRMirrorCols
         jsr   BuildHGRSparseBitmasks2Bit
         +COPY_TO_0 .start, .end
         jmp   .InputLoop
.start
!pseudopc 0 {
.Exit2Bit rts
.InputLoop
         ldy   #0
.input=*+1
         ldx   Coordinates2Bit       ; first value: HGR row + 1
         beq   .Exit2Bit             ; if 0 then we're done
         +ROW_X_TO_2BIT_BASE_ADDRESSES .src1, .src2, .dest1, .dest2

         inc   <.input
         lda   (<.input), y
         +HIGH_3_LOW_5 .input

         ; main 2x2 block in left half
.src1=*+1
         lda   $FDFD, y
         eor   (<.dest1), y
         and   copymasks2bit, x
         eor   (<.dest1), y
.dest1=*+1
         sta   $FDFD, y
.src2=*+1
         lda   $FDFD, y
         eor   (<.dest2), y
         and   copymasks2bit, x
         eor   (<.dest2), y
.dest2=*+1
         sta   $FDFD, y

         ; corresponding 2x2 block in right half (same row, opposite column)
         lda   mirror_cols, y
         tay
         +COPY_BIT .src1, .dest1, mirror_copymasks2bit
         +COPY_BIT .src2, .dest2, mirror_copymasks2bit

         inc   <.input
         bne   .InputLoop
         bit   KBD
         bmi   .Exit2Bit
         inc   <.input+1
         bne   .InputLoop            ; always branches
}
.end
}

!zone {
DHGRPrecomputed2Bit
         jsr   BuildDHGRSparseBitmasks2Bit
         jsr   BuildHGRTables
         jsr   BuildDHGRMirrorCols
         +COPY_TO_0 .start, .end
         jmp   .InputLoop

.start
!pseudopc 0 {
.Exit2Bit rts
.InputLoop
         ldy   #0
.input=*+1
         ldx   Coordinates2Bit       ; first value: HGR row + 1
         beq   .Exit2Bit             ; if 0 then we're done
         +ROW_X_TO_2BIT_BASE_ADDRESSES .src1, .src2, .dest1, .dest2

         inc   <.input
         lda   (<.input), y
         +HIGH_3_LOW_5 .input

         ; main 2x2 block in left half
         clc
-        lda   copymasks2bit, x
         beq   +
.src1=*+1
         lda   $FDFD, y
         eor   (<.dest1), y
         and   copymasks2bit, x
         eor   (<.dest1), y
.dest1=*+1
         sta   $FDFD, y
.src2=*+1
         lda   $FDFD, y
         eor   (<.dest2), y
         and   copymasks2bit, x
         eor   (<.dest2), y
.dest2=*+1
         sta   $FDFD, y
+        bcs   +
         sta   $C003
         sta   $C005
         sec
         bcs   -
+        sta   $C002
         sta   $C004

         ; corresponding 2x2 block in right half (same row, opposite column)
         lda   mirror_cols, y
         tay
         clc
-        lda   mirror_copymasks2bit, x
         beq   +
         +COPY_BIT .src1, .dest1, mirror_copymasks2bit
         +COPY_BIT .src2, .dest2, mirror_copymasks2bit
+        bcs   +
         sta   $C003
         sta   $C005
         sec
         bcs   -
+        sta   $C002
         sta   $C004

         inc   <.input
         +LBNE .InputLoop
         bit   $c000
         bmi   +
         inc   <.input+1
         jmp   .InputLoop
+        rts
}
.end
}

SetupPrecomputed3Bit
         ; build regular HGR lookup tables, then split them
         jsr   BuildHGRTables
         ldx   #$BF
         ldy   #$3F
-        lda   hgrlo, x
         sta   hgrlo3c, y
         sta   hgrlo3c+$40, y
         lda   hgrhi, x
         sta   hgrhi3c, y
         sta   hgrhi3c+$40, y
         dex
         lda   hgrlo, x
         sta   hgrlo3b, y
         sta   hgrlo3b+$40, y
         lda   hgrhi, x
         sta   hgrhi3b, y
         sta   hgrhi3b+$40, y
         dex
         lda   hgrlo, x
         sta   hgrlo3a, y
         sta   hgrlo3a+$40, y
         lda   hgrhi, x
         sta   hgrhi3a, y
         sta   hgrhi3a+$40, y
         dex
         dey
         bpl   -

         ; build lookup table to get $20+y for y in $00..$07
         ldx   #$07
         ldy   #$27
-        tya
         sta   extra_cols-$20, y
         dey
         dex
         bpl   -

         ; build sparse lookup tables for bitmasks
         lda   #%10000011
         sta   copymasks3bit

         lda   #%10001100
         sta   copymasks3bit+$20

         lda   #%10110000
         sta   copymasks3bit+$40

         lda   #%11000000
         sta   copymasks3bit+$60

         lda   #%10000001
         sta   copymasks3bit+$80

         lda   #%10000110
         sta   copymasks3bit+$A0

         lda   #%10011000
         sta   copymasks3bit+$C0

         lda   #%11100000
         sta   copymasks3bit+$E0
         rts

ReverseCoordinates3Bit
         ldy   #0                    ; <Coordinates3Bit
         sty   $f0
         lda   #>Coordinates3Bit
         sta   $f1
         lda   #<(EndCoordinates3Bit - 2)
         sta   $f2
         lda   #>(EndCoordinates3Bit - 2)
         sta   $f3

         ldx   #$28                  ; #$50/2
         clc
         !byte $24
-        sec
--       lda   ($f0), y
         pha
         lda   ($f2), y
         sta   ($f0), y
         pla
         sta   ($f2), y
         iny
         bcc   -
         ldy   #0
         !byte $24
-        clc
         inc   $f0
         bne   +
         inc   $f1
         dex
         beq   ++
+        lda   $f2
         bne   +
         dec   $f3
+        dec   $f2
         bcs   -
         bcc   --                    ; always branches
++       rts

RippleCoordinates3Bit
         ldx   #$1B
-        lda   @ripplezp, x
         sta   $e0, x
         dex
         bpl   -

---      ldx   #$0c
--       ldy   $ee, x
         lda   $ef, x
         jsr   @aslmod
         sty   $ee, x
         sta   $ef, x
         sty   $ec
         clc
         adc   #>Coordinates3Bit
         sta   $ed
         ldy   #0
         !byte $24
-        sec
         lda   ($ec), y
         pha
         lda   $de, x
         sta   ($ec), y
         pla
         sta   $de, x
         inx
         iny
         bcc   -
         dex
         dex
         dex
         dex
         bne   --
         dec   $ee
         bne   ---
         dec   $ef
         bpl   ---
         bmi   @exit                 ; always branches
@aslmod  jsr   +
+        cmp   #$28
         bcc   +
         iny
+        pha
         tya
         asl
         tay
         pla
         rol
         cmp   #$50
         bcc   @exit
         sbc   #$50
@exit    rts
@ripplezp
         !byte $1F,$F3,$20,$F3,$20,$14,$20,$D3
         !byte $1E,$F3,$1F,$54,$00,$00,$AA,$06
         !byte $02,$00,$04,$00,$06,$00,$0C,$00
         !byte $16,$00,$1A,$00

!zone {
HGRPrecomputed3Bit
         jsr   SetupPrecomputed3Bit
         +COPY_TO_0 .start, .end
         jmp   .InputLoop
.start
!pseudopc 0 {
.Exit3Bit rts
.InputLoop
         ldy   #0
.input=*+1
         lda   Coordinates3Bit
         bmi   .Exit3Bit             ; if high bit is 1 then we're done
         cmp   #$40
         php
         tax
         +ROW_X_TO_3BIT_BASE_ADDRESSES .src1, .src2, .src3, .dest1, .dest2, .dest3

         inc   <.input
         lda   (<.input), y
         and   #%11100000
         tax
         eor   (<.input), y
         plp
         bcc   +
         tay
         lda   extra_cols, y
+        tay

         ; 2x3 block
.src1=*+1
         lda   $FDFD, y
         eor   (<.dest1), y
         and   copymasks3bit, x
         eor   (<.dest1), y
.dest1=*+1
         sta   $FDFD, y
.src2=*+1
         lda   $FDFD, y
         eor   (<.dest2), y
         and   copymasks3bit, x
         eor   (<.dest2), y
.dest2=*+1
         sta   $FDFD, y
.src3=*+1
         lda   $FDFD, y
         eor   (<.dest3), y
         and   copymasks3bit, x
         eor   (<.dest3), y
.dest3=*+1
         sta   $FDFD, y

         inc   <.input
         bne   .InputLoop
         bit   KBD
         bmi   .Exit3Bit
         inc   <.input+1
         bne   .InputLoop            ; always branches
}
.end
}