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; sprite code JSL
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dcb "INIT"
dcb "MAIN"
PHB
PHK
PLB
JSR SPRITE_CODE_START
PLB
RTL
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; main bullet bill shooter code
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RETURN2 RTS ; return
SPRITE_CODE_START LDA $17AB,x ; \ return if it's not time to generate
BNE RETURN2 ; /
LDA #$40 ; \ set time till next generation = 40
STA $17AB,x ; /
LDA $178B,x ; \ don't generate if off screen vertically
CMP $1C ; |
LDA $1793,x ; |
SBC $1D ; |
BNE RETURN2 ; /
LDA $179B,x ; \ don't generate if off screen horizontally
CMP $1A ; |
LDA $17A3,x ; |
SBC $1B ; |
BNE RETURN2 ; /
LDA $179B,x ; \ ?? something else related to x position of generator??
SEC ; |
SBC $1A ; |
CLC ; |
ADC #$10 ; |
CMP #$10 ; |
BCC RETURN2 ; /
JSL $02A9DE ; \ get an index to an unused sprite slot, return if all slots full
BMI RETURN2 ; / after: Y has index of sprite being generated
GENERATE_SPRITE LDA #$09 ; \ play sound effect
STA $1DFC ; /
LDA #$01 ; \ set sprite status for new sprite
STA $14C8,y ; /
LDA #$9F ; \ set sprite number for new sprite
STA $009E,y ; /
LDA $179B,x ; \ set x position for new sprite
STA $00E4,y ; |
LDA $17A3,x ; |
STA $14E0,y ; /
LDA $178B,x ; \ set y position for new sprite
SEC ; | (y position of generator - 1)
SBC #$01 ; |
STA $00D8,y ; |
LDA $1793,x ; |
SBC #$00 ; |
STA $14D4,y ; /
PHX ; \ before: X must have index of sprite being generated
TYX ; | routine clears old sprite values...
JSL $07F7D2 ; | ...and loads in new values for the 6 main sprite tables
PLX ; /
LDA #$08 ;
STA $14C8,y ;
LDA $00
PHA
LDA $1783,x
AND #$40
BEQ LEFT
LDA $178B,x ; check y position and shoot up or down accordingly
AND #$10 ; todo: change this check
BNE SHOOT_UP2
LDA #$03
BRA STORE
SHOOT_UP2 LDA #$03
BRA STORE
LEFT LDA $178B,x ; check y position and shoot up or down accordingly
AND #$10 ; todo: change this check
BNE SHOOT_UP
LDA #$01
BRA STORE
SHOOT_UP LDA #$01
STORE STA $00C2,y ; 06 for down, 07 for up
STA $00
JSR SUB_SMOKE2
PLA
STA $00
RETURN RTS ; return
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; display smoke effect for diagonal shooter
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;up left, down right, down left, up right,
Y_OFFSET dcb $00,$00,$00,$00,$FA,$04,$04,$FA
X_OFFSET dcb $00,$00,$00,$00,$04,$04,$FA,$FA
SUB_SMOKE2 LDY #$03 ; \ find a free slot to display effect
FINDFREE LDA $17C0,y ; |
BEQ FOUNDONE ; |
DEY ; |
BPL FINDFREE ; |
RTS ; / return if no slots open
FOUNDONE LDA #$01 ; \ set effect graphic to smoke graphic
STA $17C0,y ; /
LDA $178B,x ; \
PHX ; |
PHA ; |
LDA $00
TAX
PLA ; | set smoke y position based on direction of shot
CLC ; |
ADC Y_OFFSET,x ; |
STA $17C4,y ; /
PLX
LDA #$1B ; \ set time to show smoke
STA $17CC,y ; /
LDA $179B,x ; \ load generator x position
PHX
PHA
LDA $00
TAX
PLA
CLC ; |
ADC X_OFFSET,x
STA $17C8,y ; /
PLX
RTS
Danke WYE 
)
