51 lines
668 B
ArmAsm
51 lines
668 B
ArmAsm
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move_ducks:
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ldx #1 ; start with duck2
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move_duck_loop:
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clc
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lda D1_XPOS,X
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adc D1_XSPEED,X
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sta D1_XPOS,X
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; check out of bounds
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; duck XPOS is middle of duck (which is 12 wide)
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;
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; to stay in pond want XPOS to be between and 8 and 34?
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lda D1_XPOS,X
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cmp #8
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bcc duck_too_far_left ; blt
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cmp #34
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bcs duck_too_far_right ; bge
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jmp duck_good
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duck_too_far_left:
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lda #$1 ; move right
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sta D1_XSPEED,X
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lda D1_STATE,X ; face right
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ora #DUCK_RIGHT
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sta D1_STATE,X
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jmp duck_good
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duck_too_far_right:
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lda #$ff ; move left
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sta D1_XSPEED,X
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lda D1_STATE,X ; face left
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and #<~DUCK_RIGHT
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sta D1_STATE,X
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duck_good:
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dex
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bpl move_duck_loop
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rts
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