4cade/src/fx/fx.hgr.meet.in.the.middle.a

;license:MIT
;(c) 2019 by 4am
;
!cpu 6502
!to "build/FX.INDEXED/MEETINTHEMIDDLE",plain
*=$6000

maskindex = $fc
row = $fd
col1 = $fe
col2 = $ff

         !source "src/fx/macros.a"
         !source "src/constants.a"

         lda   #0
         sta   col1
         lda   #39
         sta   col2
@colloop
         lda   #6
         sta   maskindex
         jsr   WaitForVBL
@maskloop
         ldx   maskindex
         lda   copymasks1,x
         sta   @copymask1
         lda   copymasks2,x
         sta   @copymask2

         lda   #23
         sta   row
@rowloop
         lda   row
         asl
         asl
         asl
         jsr   HGRCalc
         clc
         ldx   #8
@blockloop
         ldy   col1
         lda   ($26),y
         eor   ($3c),y
@copymask1=*+1
         and   #0                    ; SMC
         eor   ($26),y
         sta   ($26),y

         ldy   col2
         lda   ($26),y
         eor   ($3c),y
@copymask2=*+1
         and   #0                    ; SMC
         eor   ($26),y
         sta   ($26),y

         lda   $27
         adc   #4
         sta   $27
         eor   #$60
         sta   $3d
         dex
         bne   @blockloop

         dec   row
         bpl   @rowloop

         lda   #1
         jsr   iWaitForKeyWithTimeout
         bmi   @exit
         dec   maskindex
         bpl   @maskloop
         inc   col1
         dec   col2
         lda   col1
         cmp   #20
         bne   @colloop
@exit    jmp   UnwaitForVBL
copymasks1
         !byte %11111111
         !byte %10111111
         !byte %10011111
         !byte %10001111
         !byte %10000111
         !byte %10000011
         !byte %10000001
copymasks2
         !byte %11111111
         !byte %11111110
         !byte %11111100
         !byte %11111000
         !byte %11110000
         !byte %11100000
         !byte %11000000

         +HGR_CALC_ROUTINES