93 lines
1.3 KiB
ArmAsm
93 lines
1.3 KiB
ArmAsm
; Checkers, based on the code in Hellmood's Memories
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; 42 bytes
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; could be shorter if you're not picky about colors
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; by deater (Vince Weaver) <vince@deater.net>
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; Zero Page
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BASL = $28
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BASH = $29
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H2 = $2C
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COLOR = $30
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X1 = $F0
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X2 = $F1
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Y1 = $F2
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Y2 = $F3
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TEMP = $FA
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TEMPY = $FB
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FRAME = $FC
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TEMPX = $FD
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; Soft Switches
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KEYPRESS= $C000
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KEYRESET= $C010
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SET_GR = $C050 ; Enable graphics
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FULLGR = $C052 ; Full screen, no text
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PAGE0 = $C054 ; Page0
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PAGE1 = $C055 ; Page1
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LORES = $C056 ; Enable LORES graphics
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; ROM routines
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PLOT = $F800 ; plot, horiz=y, vert=A (A trashed, XY Saved)
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SETCOL = $F864
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TEXT = $FB36 ;; Set text mode
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BASCALC = $FBC1
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SETGR = $FB40
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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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HLINE = $F819
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.zeropage
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; orig = 42
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; make 32x32
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checkers:
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;===================
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; init screen
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jsr SETGR ; 3
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; bit FULLGR ; 3
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;====
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; 6
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checkers_forever:
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inc FRAME ; 2
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; ldx #39 ; 2
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yloop:
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; ldy #39 ; 2
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xloop:
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; sec ; 1
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tya ; 1
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sbc FRAME ; 2
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sta X2 ; 2
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txa ; 1
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sbc #0 ; 2
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eor X2 ; 2
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ora #$DC ; 2
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; adc #1 ; 2
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sta COLOR
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; jsr SETCOL ; 3
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txa ; A==Y1 ; 1
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jsr PLOT ; (X2,Y1) ; 3
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dey ; 1
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bpl xloop ; 2
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dex ; 1
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bpl yloop ; 2
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bmi checkers_forever ; 2
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