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90 lines
1.4 KiB
Plaintext
90 lines
1.4 KiB
Plaintext
;license:MIT
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;(c) 2020 by qkumba
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;
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coord = $FE
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Coordinates = $7000 ; about $700 bytes, can be anywhere
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!source "src/fx/macros.a"
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!macro BUILD_BLOCK_FIZZLE_DATA {
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+LDADDR Coordinates
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+ST16 coord
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;init RNG
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ldx #1
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stx @rnd1+1
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dex
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stx @rnd2+1
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;iterate
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@loop
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ldy @rnd1+1
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ldx @rnd2+1
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lsr @rnd2+1
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ror @rnd1+1
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bcc +
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;feedback polynomial forms #$204 for period of 1023
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lda @rnd1+1
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eor #4
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sta @rnd1+1
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lda @rnd2+1
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eor #2
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sta @rnd2+1
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+ tya
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eor #$ff
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ldy #0
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- cpx #0
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bne +
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cmp #40
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bcc ++
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+ sbc #40
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pha
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txa
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sbc #0
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tax
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pla
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iny
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bne -
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++ cpy #24
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bcs @rnd2
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tax
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tya
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jsr @stainc
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txa
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jsr @stainc
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@rnd2 lda #0
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bne @loop
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@rnd1 lda #0
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cmp #1
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bne @loop
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;include the missing point
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lda #6
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jsr @stainc
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lda #15
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jsr @stainc
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lda #$ff
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jsr @stainc
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bne ++ ; always branches
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@stainc
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ldy #0
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sta (coord), y
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inc coord
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bne +
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inc coord+1
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+ rts
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++
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}
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