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Define a constant for shot array length.

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This commit is contained in:
Colin McMillen 2015-05-27 07:51:51 -04:00
parent c94ac75c45
commit 7b637436b8
1 changed files with 10 additions and 9 deletions
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19
pewpew.asm
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@ -32,7 +32,8 @@
.define playerY $21 .define playerY $21
.define shotCooldown $22 .define shotCooldown $22
.define nextShotPtr $23 .define nextShotPtr $23
.define shotData $30 .define shotArray $30
.define shotArrayLength 4
; TODO(mcmillen): verify that we can relocate these without messing things up. ; TODO(mcmillen): verify that we can relocate these without messing things up.
.define spriteTableStart $100 .define spriteTableStart $100
@ -293,7 +294,7 @@ InitializeWorld:
sta playerY sta playerY
; Next shot pointer starts at the beginning. ; Next shot pointer starts at the beginning.
ldx #shotData ldx #shotArray
stx nextShotPtr stx nextShotPtr
rts rts
@ -455,9 +456,9 @@ MaybeShoot:
.rept 4 .rept 4
inx inx
.endr .endr
cpx #$0040 ; TODO(mcmillen): use a constant. cpx #(shotArray + shotArrayLength * 4)
bne + bne +
ldx #shotData ldx #shotArray
+ +
stx nextShotPtr stx nextShotPtr
@ -505,22 +506,22 @@ UpdateWorld:
UpdateShot: UpdateShot:
lsr $00 lsr $00
lsr $00 lsr $00
lda shotData, X lda shotArray, X
cmp #1 cmp #1
bne DisableShot bne DisableShot
; Add to the x-coordinate. If the carry bit is set, we went off the edge ; Add to the x-coordinate. If the carry bit is set, we went off the edge
; of the screen, so disable the shot. ; of the screen, so disable the shot.
lda shotData + 1, X lda shotArray + 1, X
clc clc
adc #6 ; x velocity adc #6 ; x velocity
bcs DisableShot bcs DisableShot
sta shotData + 1, X ; Store new x-coord. sta shotArray + 1, X ; Store new x-coord.
; Set up shot in sprite table. ; Set up shot in sprite table.
lda shotData + 1, X ; x lda shotArray + 1, X ; x
; TODO(mcmillen): document that shots start at $110? ; TODO(mcmillen): document that shots start at $110?
sta $0110, X sta $0110, X
lda shotData + 2, X ; y lda shotArray + 2, X ; y
sta $0111, X sta $0111, X
lda #8 ; which sprite? lda #8 ; which sprite?
sta $0112, X sta $0112, X