dos33fsprogs/graphics/gr/checkers/checkers_2000.s
2021-07-26 01:29:42 -04:00

99 lines
1.3 KiB
ArmAsm

; Checkers
; vaguely based on a scene in Hellmood's Memories
; 32 bytes, for Lovebyte 2021
; by deater (Vince Weaver) <vince@deater.net>
; 42 -- original
; 39 -- not fullscreen
; 36 -- now marches oddly
; 32 -- colors now rainbow
; Zero Page
BASL = $28
BASH = $29
H2 = $2C
COLOR = $30
X1 = $F0
X2 = $F1
Y1 = $F2
Y2 = $F3
TEMP = $FA
TEMPY = $FB
FRAME = $FC
TEMPX = $FD
; Soft Switches
KEYPRESS= $C000
KEYRESET= $C010
SET_GR = $C050 ; Enable graphics
FULLGR = $C052 ; Full screen, no text
PAGE0 = $C054 ; Page0
PAGE1 = $C055 ; Page1
LORES = $C056 ; Enable LORES graphics
; ROM routines
PLOT = $F800 ; plot, horiz=y, vert=A (A trashed, XY Saved)
SETCOL = $F864
TEXT = $FB36 ;; Set text mode
BASCALC = $FBC1
SETGR = $FB40
HOME = $FC58 ;; Clear the text screen
WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us
HLINE = $F819
.zeropage
checkers:
;===================
; init screen
jsr SETGR ; 3
; bit FULLGR ; 3
checkers_forever:
inc FRAME ; 2
ldx #39 ; 2
yloop:
ldy #39 ; 2
xloop:
; calculate color
; color = (XX-FRAME)^(A) | DB+1
; sec ; subtract frame from Y
tya
sbc FRAME
sta X2
txa
; sbc #0
eor X2
; ora #$DB ; needed for solid colors
; adc #1
jsr SETCOL
txa ; A==Y1 ; 1
jsr PLOT ; plots in (Y,A) ; 3
dey ; 1
bpl xloop ; 2
dex ; 1
bpl yloop ; 2
bmi checkers_forever ; 2