184 lines
2.2 KiB
ArmAsm
184 lines
2.2 KiB
ArmAsm
; Moon
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; by deater (Vince Weaver) <vince@deater.net>
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; Zero Page
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GBASL = $26
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GBASH = $27
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COLOR = $30
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SEEDL = $43
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SEEDH = $44
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FRAME = $EA
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FRAME2 = $EB
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FRAME4 = $EC
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TEMP = $FC
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PAGE = $FD
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COUNT = $FE
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WHICH = $FF
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; Soft Switches
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SET_GR = $C050 ; Enable graphics
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FULLGR = $C052 ; Full screen, no text
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PAGE1 = $C054 ; Page1
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PAGE2 = $C055 ; Page2
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LORES = $C056 ; Enable LORES graphics
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; ROM routines
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GBASCALC= $F847 ; take Y-coord/2 in A, put address in GBASL/H ( a trashed, C clear)
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SETGR = $FB40
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WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us
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PLOT = $F800 ;; PLOT AT Y,A
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SETCOL = $F864 ;; COLOR=A
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moon:
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;===================
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; init screen
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jsr SETGR ; lores graphics
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bit FULLGR ; full screen
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lda #$0 ; start on page1
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sta PAGE
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;parallax_forever:
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; inc FRAME ; increment frame
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;
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; lda FRAME ; also have frame/2 and frame/4
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; lsr
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; sta FRAME2
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; lsr
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; sta FRAME4
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;==========================
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; flip page
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; lda PAGE ; get current page
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; pha ; save for later
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; lsr ; switch visible page
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; lsr
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; tay
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; lda PAGE1,Y
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; pla ; save old draw page
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; eor #$4 ; toggle to other draw page
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; sta PAGE
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big_loop:
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lda #$66
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sta COLOR
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ldx #24
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stx COUNT
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water:
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ldx COUNT
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jsr get_z
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sta TEMP
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asl
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asl
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asl
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tax
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water_line:
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jsr random
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adc FRAME
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adc COUNT
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and #$1F
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tay
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lda COUNT
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clc
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adc #23
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jsr PLOT ; plot at Y,A
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skip:
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dex
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bne water_line
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dec COUNT
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bne water
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over:
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lda #1
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sta SEEDL
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lda #1
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sta SEEDH
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inc FRAME
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lda #100
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jsr WAIT
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jsr clear_bottom
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jmp big_loop
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; from batari basic (?)
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random:
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lda SEEDH
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lsr
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rol SEEDL
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bcc noeor
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eor #$B4
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noeor:
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sta SEEDH
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eor SEEDL
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rts
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get_z:
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lda #1
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cpx #10
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bcs done_z
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lda Z_lookup,X
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done_z:
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rts
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HLIN = $F819 ; HLINE Y,$2C at A
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clear_bottom:
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lda #0
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sta COLOR
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lda #24
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sta WHICH
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clear_bottom_loop:
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ldy #0
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lda #39
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sta $2C
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lda WHICH
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cmp #48
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beq done_clear
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jsr HLIN
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inc WHICH
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bne clear_bottom_loop
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done_clear:
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rts
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Z_lookup:
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.byte 24, 12, 8, 6, 5, 4, 3, 3
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.byte 2, 2
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;20 FOR Y=0 TO 24
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;30 Z=24/(Y+1)
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;40 FOR I=0 TO Z*4
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;50 X=INT(RND(1)*39)+T*150/Z
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;'60 W=COS(RND(1)+T)*12/Z
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;65 C=SCRN(X,20-Y/2):IF C=0 THEN C=6
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;70 COLOR=C:PLOT X,Y+20
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;80 NEXT:NEXT:GOTO 20
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