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https://github.com/deater/dos33fsprogs.git
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80 lines
1.5 KiB
ArmAsm
80 lines
1.5 KiB
ArmAsm
; Puffball
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; 31 byte rotating Apple II shapetables
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; for Lovebyte 2024
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; by Vince `deater` Weaver / DsR
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; zero page locations
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GBASL = $26
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GBASH = $27
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HGR_HORIZ = $E5
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HGR_SCALE = $E7
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HGR_COLLISION = $E8
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HGR_ROTATION = $00 ; usually $F9 but can't here
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; ROM locations
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HGR2 = $F3D8
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HPOSN = $F411
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XDRAW0 = $F65D
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XDRAW1 = $F661
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HPLOT0 = $F457
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.zeropage
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.globalzp blip
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puffball:
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; we load at $E7 so HGR_SIZE set to $20 (first byte of JSR)
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jsr HGR2 ; Hi-res, full screen ; $E7/$E8/$E9
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; Y=0, A=0 after this call
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nop ; EA HGR_COLLISION) ; $EA
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; A and Y are 0 here.
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; X is left behind by the boot process?
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tiny_loop:
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; A=0 here from both cases
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; we need the following values to start at center
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; directly would need to set 16 bytes
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; GBASL=$28
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; GBASH=$42
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; HGR_HORIZ=20
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; HMASK=$81
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tay ; ldy #0 ; $EB
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ldx #140 ; $EC/$ED
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lda #96 ; $EE/$EF
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jsr HPOSN ; set screen position to X= (y,x) Y=(a) ; $F0/$F1/$F2
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; saves X,Y,A to zero page
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; after Y= orig X/7
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; A and X are ??
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blip:
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ldx #<our_shape ; ; $F3/$F4
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ldy #>our_shape ; ; $F5/$F6
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inc HGR_ROTATION ; $F7/$F8
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lda HGR_ROTATION ; $F9/$FA
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and #$3f ; $FB/$FC
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bne ee ; $FD/$FE
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dec blip+1 ;(blip+1) ; $FF/$100
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ee:
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jsr XDRAW0 ; XDRAW 1 AT X,Y ; $101/$102/$103
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; Both A and X are 0 at exit
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; Z flag set on exit
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; Y varies
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beq tiny_loop ; bra ; $104/$105
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our_shape=$E2E2
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; values at $E2DF
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;our_shape:
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;.byte $11,$f0,$03,$20,$00
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