mirror of
https://github.com/fumiama/c64-snake.git
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86 lines
1.2 KiB
NASM
86 lines
1.2 KiB
NASM
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; move 根据d中的值实现蛇的移动
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move:
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.scope
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;lda #1 ;演示用
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;sta eat
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lda eat ;eat判断，进入两种移动模式
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;bne +++++ ;进入模式一：四种移动模式（吃到）（头动，尾不动）
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lda d
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;lda #go_l ;测试用
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cmp #go_d
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bne +
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clc
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lda shead ;new head
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adc #40
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sta shead
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lda shead+1
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adc #0
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sta shead+1
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ldy #0 ;head move down
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lda #csnk
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sta (shead),y
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rts
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* cmp #go_r
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bne +
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clc
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lda shead ;new head
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adc #1
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sta shead
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lda shead+1
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adc #0
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sta shead+1
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ldy #0 ;head move right
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lda #csnk
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sta (shead),y
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rts
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* cmp #go_l
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bne +
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clc
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lda shead ;new head
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sec
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sbc #1
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sta shead
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lda shead+1
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sbc #0
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sta shead+1
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ldy #0 ;head move left
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lda #csnk
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sta (shead),y
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rts
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* cmp #go_u
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bne +
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clc
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lda shead ;new head
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sec
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sbc #40
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sta shead
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lda shead+1
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sbc #0
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sta shead+1
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ldy #0 ;head move up
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lda #csnk
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sta (shead),y
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* rts
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;模式二：四种移动模式
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; lda d
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; lda #go_d ;实验用
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; cmp go_d
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; beq +
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; lda #csps
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; ldy #0
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; sta (shead),y
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; lda #csnk
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; ldy #40
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; sta (shead),y
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; clc
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; lda shead
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; adc #40
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; sta shead
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; lda shead+1
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; adc #0
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; sta shead+1
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;* rts
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.scend |