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Updating the demo.asm

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Safiire 2015-03-02 21:27:53 -08:00
parent d67d1a6693
commit 2dca12a519
1 changed files with 29 additions and 29 deletions
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58
demo.asm
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@ -119,7 +119,7 @@ init_sound:
;;;;
; Clear page #2, which we'll use to hold sprite data
; This subroutine clearlys hows why I need to have symbols
; This subroutine clearly shows why I need to have symbols
; to refer to bits of RAM in the zero page like dx, etc.
init_sprites:
lda #$00
@ -133,8 +133,8 @@ init_sprites:
lda #$70
sta $0200 ; sprite Y coordinate
lda #$01
sta $0201 ; sprite + 1Pattern number
sta $0203 ; sprite+3 X coordinate sprite+2, color, stays 0.
sta $0201 ; sprite + 1 Pattern number
sta $0203 ; sprite + 3 X coordinate, sprite + 2, color, stays 0.
; Set initial value of dx
lda #$01
@ -243,38 +243,38 @@ react_to_input:
sta $01 ; Store the 1 in local variable 'a' so that we this is
jsr reverse_dx ; only called once per press.
jmp a_done
not_a:
sta $01 ; A has been released, so put that zero into 'a'.
a_done:
lda $4016 ; B does nothing
lda $4016 ; Select does nothing
lda $4016 ; Start does nothing
lda $4016 ; Up
and #$01
beq not_up
ldx sprite ; Load Y value
cpx #$07
beq not_up ; No going past the top of the screen
dex
stx sprite
not_a:
sta $01 ; A has been released, so put that zero into 'a'.
a_done:
lda $4016 ; B does nothing
lda $4016 ; Select does nothing
lda $4016 ; Start does nothing
lda $4016 ; Up
and #$01
beq not_up
ldx sprite ; Load Y value
cpx #$07
beq not_up ; No going past the top of the screen
dex
stx sprite
not_up:
lda $4016 ; Down
and #$01
beq not_dn
ldx sprite
cpx #$DF ; No going past the bottom of the screen.
beq not_dn
inx
stx sprite
not_dn:
not_up:
lda $4016 ; Down
and #$01
beq not_dn
ldx sprite
cpx #$DF ; No going past the bottom of the screen.
beq not_dn
inx
stx sprite
not_dn:
rts ; Ignore left and right, we don't use 'em
reverse_dx:
lda #$FF
eor $00 ; dx
eor $00 ; dx Toggles between 0x1 and 0xfe (-1)
clc
adc #$01
adc #$01 ; add dx, and store to variable
sta $00 ; dx
jsr low_c
rts