Crappy C64 Matrix Screensaver

    processor 6502
    org $1000

    lda #$00
    sta $D020
    sta $D021
    lda #$04
    sta $2200
    lda #$02
    sta $2201
    lda #$01
    sta $2202
    lda #$07
    sta $2203
    lda #$04
    sta $2204
    lda #$06
    sta $2205
    lda #$05
    sta $2206
    lda #$03
    sta $2207
    lda #$05
    sta $2208
    lda #$04
    sta $2209
    lda #$08
    sta $220A
    lda #$07
    sta $220B
    lda #$04
    sta $220C
    lda #$06
    sta $220D
    lda #$02
    sta $220E
    lda #$04
    sta $220F
    lda #$01
    sta $2210
    lda #$02
    sta $2211
    lda #$05
    sta $2212
    lda #$09
    sta $2213
    lda #$05
    sta $2214
    lda #$07
    sta $2215
    lda #$03
    sta $2216
    lda #$05
    sta $2217
    lda #$08
    sta $2218
    lda #$02
    sta $2219
    lda #$05
    sta $221A
    lda #$03
    sta $221B
    lda #$05
    sta $221C
    lda #$08
    sta $221D
    lda #$03
    sta $221E
    lda #$05
    sta $221F
    lda #$01
    sta $2220
    lda #$03
    sta $2221
    lda #$04
    sta $2222
    lda #$06
    sta $2223
    lda #$03
    sta $2224
    lda #$07
    sta $2225
    lda #$04
    sta $2226
    lda #$06
    sta $2227
    lda #$06
    sta $2100
    lda #$03
    sta $2101
    lda #$06
    sta $2102
    lda #$01
    sta $2103
    lda #$06
    sta $2104
    lda #$00
    sta $2105
    lda #$05
    sta $2106
    lda #$07
    sta $2107
    lda #$03
    sta $2108
    lda #$05
    sta $2109
    lda #$02
    sta $210A
    lda #$07
    sta $210B
    lda #$06
    sta $210C
    lda #$04
    sta $210D
    lda #$05
    sta $210E
    lda #$01
    sta $210F
    lda #$02
    sta $2110
    lda #$07
    sta $2111
    lda #$08
    sta $2112
    lda #$00
    sta $2113
    lda #$07
    sta $2114
    lda #$05
    sta $2115
    lda #$04
    sta $2116
    lda #$03
    sta $2117
    lda #$02
    sta $2118
    lda #$05
    sta $2119
    lda #$06
    sta $211A
    lda #$05
    sta $211B
    lda #$03
    sta $211C
    lda #$01
    sta $211D
    lda #$02
    sta $211E
    lda #$05
    sta $211F
    lda #$09
    sta $2120
    lda #$08
    sta $2121
    lda #$06
    sta $2122
    lda #$05
    sta $2123
    lda #$07
    sta $2124
    lda #$04
    sta $2125
    lda #$06
    sta $2126
    lda #$03
    sta $2127
    lda #$04
    sta $2000
    lda #$07
    sta $2001
    lda #$04
    sta $2002
    lda #$08
    sta $2003
    lda #$07
    sta $2004
    lda #$02
    sta $2005
    lda #$04
    sta $2006
    lda #$04
    sta $2007
    lda #$08
    sta $2008
    lda #$06
    sta $2009
    lda #$01
    sta $200A
    lda #$02
    sta $200B
    lda #$02
    sta $200C
    lda #$05
    sta $200D
    lda #$03
    sta $200E
    lda #$07
    sta $200F
    lda #$06
    sta $2010
    lda #$00
    sta $2011
    lda #$04
    sta $2012
    lda #$01
    sta $2013
    lda #$05
    sta $2014
    lda #$02
    sta $2015
    lda #$03
    sta $2016
    lda #$06
    sta $2017
    lda #$05
    sta $2018
    lda #$03
    sta $2019
    lda #$01
    sta $201A
    lda #$07
    sta $201B
    lda #$04
    sta $201C
    lda #$02
    sta $201D
    lda #$06
    sta $201E
    lda #$05
    sta $201F
    lda #$00
    sta $2020
    lda #$04
    sta $2021
    lda #$08
    sta $2022
    lda #$04
    sta $2023
    lda #$07
    sta $2024
    lda #$02
    sta $2025
    lda #$05
    sta $2026
    lda #$03
    sta $2027
loop:
    lda $D012
    cmp #$FF
    bne loop
    ldx #39
handle:
    lda $2400,X
    cmp $2200,X
    bne skip5
    ldy $2600,X
    lda $2500,X
    cmp #$01
    beq undraw1
    cmp #$02
    beq undraw2
    cmp #$03
    beq undraw3
    cmp #$04
    beq undraw4
    jmp yep
undraw1:
    lda #$05
    sta $D800,Y
    jmp yep
undraw2:
    lda #$05
    sta $D900,Y
    jmp yep
undraw3:
    lda #$05
    sta $DA00,Y
    jmp yep
undraw4:
    lda #$05
    sta $DB00,Y
yep:
    lda #$00
    sta $2400,X
    lda $2100,X
    ldy #39
    jmp multiply
return:
    stx $2300
    clc
    adc $2300
    bcc skip2
    inc $2303
skip2:
    tay
    dey
    lda $2000,X
    sty $2304
    ldy $2303
    cpy #$00
    beq draw1
    cpy #$01
    beq draw2
    cpy #$02
    beq draw2
    cpy #$03
    beq draw3
    cpy #$04
    beq draw3
    jmp draw4
skip5:
    jmp skip4
handle2:
    jmp handle
draw1:
    ldy $2304
    sta $0400,Y
    lda #$07
    sta $D800,Y
    lda #$01
    sta $2500,X
    tya
    sta $2600,X
    jmp done
draw2:
    ldy $2304
    sta $0500,Y
    lda #$07
    sta $D900,Y
    lda #$02
    sta $2500,X
    tya
    sta $2600,X
    jmp done
draw3:
    ldy $2304
    sta $0600,Y
    lda #$07
    sta $DA00,Y
    lda #$03
    sta $2500,X
    tya
    sta $2600,X
    jmp done
draw4:
    ldy $2304
    sta $0700,Y
    lda #$07
    sta $DB00,Y
    lda #$04
    sta $2500,X
    tya
    sta $2600,X
done:
    inc $2100,X
    lda $2100,X
    cmp #$19
    bne skip3
    lda #$00
    sta $2100,X
skip3:
    inc $2000,X
    lda $2000,X
    cmp #$80
    bne skip4
    lda #$00
    sta $2000,X
skip4:
    inc $2400,X
    dex
    bne handle2
    jmp loop
multiply:
    sty $2300
    sta $2301
    stx $2302
    ldx #$00
    stx $2303
add:
    clc
    adc $2301
    bcc skip
    tax
    lda $2303
    adc #$01
    sta $2303
    txa
skip:
    dey
    bne add
    ldy $2300
    ldx $2302
    jmp return