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; Conway\'s Game of Life
; http://rosettacode.org/wiki/Conway\'s_Game_of_Life
; Submitted by Anonymous
randfill: stx $01 ;$200 for indirect
ldx #$02 ;addressing
stx $02
randloop: lda $fe ;generate random
and #$01 ;pixels on the
sta ($01),Y ;screen
jsr inc0103
cmp #$00
bne randloop
lda $02
cmp #$06
bne randloop
clearmem: lda #$df ;set $07df-$0a20
sta $01 ;to $#00
lda #$07
sta $02
clearbyte: lda #$00
sta ($01),Y
jsr inc0103
cmp #$20
bne clearbyte
lda $02
cmp #$0a
bne clearbyte
starttick:
copyscreen: lda #$00 ;set up source
sta $01 ;pointer at
sta $03 ;$01/$02 and
lda #$02 ;dest pointer
sta $02 ;at $03/$04
lda #$08
sta $04
ldy #$00
copybyte: lda ($01),Y ;copy pixel to
sta ($03),Y ;back buffer
jsr inc0103 ;increment pointers
cmp #$00 ;check to see
bne copybyte ;if we\'re at $600
lda $02 ;if so, we\'ve
cmp #$06 ;copied the
bne copybyte ;entire screen
conway: lda #$df ;apply conway rules
sta $01 ;reset the pointer
sta $03 ;to $#01df/$#07df
lda #$01 ;($200 - $21)
sta $02 ;($800 - $21)
lda #$07
sta $04
onecell: lda #$00 ;process one cell
ldy #$01 ;upper cell
clc
adc ($03),Y
ldy #$41 ;lower cell
clc
adc ($03),Y
chkleft: tax ;check to see
lda $01 ;if we\'re at the
and #$1f ;left edge
tay
txa
cpy #$1f
beq rightcells
leftcells: ldy #$00 ;upper-left cell
clc
adc ($03),Y
ldy #$20 ;left cell
clc
adc ($03),Y
ldy #$40 ;lower-left cell
clc
adc ($03),Y
chkright: tax ;check to see
lda $01 ;if we\'re at the
and #$1f ;right edge
tay
txa
cpy #$1e
beq evaluate
rightcells: ldy #$02 ;upper-right cell
clc
adc ($03),Y
ldy #$22 ;right cell
clc
adc ($03),Y
ldy #$42 ;lower-right cell
clc
adc ($03),Y
evaluate: ldx #$01 ;evaluate total
ldy #$21 ;for current cell
cmp #$03 ;3 = alive
beq storex
ldx #$00
cmp #$02 ;2 = alive if
bne storex ;c = alive
lda ($03),Y
and #$01
tax
storex: txa ;store to screen
sta ($01),Y
jsr inc0103 ;move to next cell
conwayloop: cmp #$e0 ;if not last cell,
bne onecell ;process next cell
lda $02
cmp #$05
bne onecell
jmp starttick ;run next tick
inc0103: lda $01 ;increment $01
cmp #$ff ;and $03 as 16-bit
bne onlyinc01 ;pointers
inc $02
inc $04
onlyinc01: inc $01
lda $01
sta $03
rts
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