175 lines
2.8 KiB
ArmAsm
175 lines
2.8 KiB
ArmAsm
; That's not a moon....
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; by Vince `deater` Weaver, dSr, Lovebyte 2021
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; based on the following BASIC program
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; 1HOME:POKE49167,0
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; 2FORX=0TO64:POKE1024+RND(1)*999,174:NEXT
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; 3FORI=0TO1:COLOR=6-I:FORJ=0TO1
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; 4HLIN8,10AT6+J*10+I:HLIN7,11AT8+J*6+I:HLIN6,12AT10+J*2+I:NEXTJ,I
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; 6VTAB6:HTAB11:?"()"
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; 7FORX=13TO37:POKE1063+X,90:POKE1064+X,91:POKE1065+X,95
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; 8FORI=1TO200:NEXT:VTAB9:HTABX:?" ":NEXT
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; 9GOTO7
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; 167 -- initial implementation
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; 170 -- smooth grey support
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; 152 -- make death star data byte array
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; 148 -- make death star VTAB not hardcoded
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; 144 -- move to zero page
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; 136 -- index into ROM for "random" numbers
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; 133 -- optimize star placement
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; 131 -- note when X already 0
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; 130 -- optimize tie erase
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; 126 -- more optimize death star drawing
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; 124 -- use the DEC CV the instruction before VTAB
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; need 124 for lovebyte
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; zero page
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CV = $25
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BASL = $28
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BASH = $29
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SEEDL = $4E
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INL = $66
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INH = $67
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; soft-switches
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MOUSETEXT = $C00F ; (write) to enable mouse text
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; rom routines
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HOME = $FC58 ; Clear the text screen
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WAIT = $FCA8 ; delay 1/2(26+27A+5A^2) us
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VTAB = $FC22 ; calc screen position in CV, put in (BASL)
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VTABZ = $FC24 ; calc screen position in A, put in (BASL)
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.zeropage
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.globalzp grey_smc,ds_data,star_store_smc,tie_data
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;=======================
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; Clear screen and setup
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;=======================
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sw:
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jsr HOME ; clear the screen
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sta MOUSETEXT ; enable mouse text
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;=======================
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; Display Stars
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;=======================
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ldx #64
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star_loop:
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lda $F100,X
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eor $F300,X ; fake random
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tay
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lda $F800,X
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eor $F900,X ; more fake random
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and #$3
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ora #$4
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sta star_store_smc+2
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lda #'.'|$80
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star_store_smc:
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sta $400,Y
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dex
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bne star_loop
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;=======================
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; Display Death Star
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;=======================
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; ldx #0 ; X already 0
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lda #9 ; count backwards
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sta CV
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ds_loop:
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;============================
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; draw grey line
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;============================
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grey_line:
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jsr $FC20 ; this is a DEC CV line before VTAB
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; jsr VTAB ; position VTAB based on CV
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sec
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lda #19
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sbc ds_data,X
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sta grey_smc+1
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ldy ds_data,X
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; inx
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; lda ds_data,X
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; sta grey_smc+1
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inx
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grey_loop:
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clc
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tya
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and #$1
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adc #$56 ; make it an even grey
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sta (BASL),Y
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iny
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grey_smc:
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cpy #0
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bne grey_loop
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; inc CV
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cpx #6
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bne ds_loop
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; draw reflector
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lda #'('+$80 ; 5,10?
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sta $68A
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lda #')'+$80 ; 5,11?
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sta $68B
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;=======================
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; Draw Tie Fighter
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;=======================
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tie_loop:
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ldy #12
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tie_move:
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; draw tie
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ldx #2
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xloop1:
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lda tie_data,X
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sta $428,Y ; line 8 (vtab 9)
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iny
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dex
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bpl xloop1
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; delay a bit
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lda #200
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jsr WAIT
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; erase
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lda #$A0 ; space (the final frontier)
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xloop2:
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dey
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sta $428,Y ; line 8 (vtab 9)
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inx
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cpx #2
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bne xloop2
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iny
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cpy #38
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bne tie_move
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beq tie_loop
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tie_data:
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.byte 95,91,90
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ds_data:
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.byte 8;,11
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.byte 7;,12
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.byte 6;,13
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.byte 6;,13
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.byte 7;,12
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.byte 8;,11
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