2019-04-25 21:17:31 +00:00
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draw_addr = $e000
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key_addr = $f001
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draw_colour_addr = $10
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loop
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lda #$0
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jsr read_key
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cmp #$0
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beq loop
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cmp #$50
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bne not_left
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jsr move_left
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clv
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bvc loop
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not_left
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cmp #$4f
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bne not_right
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jsr move_right
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clv
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bvc loop
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not_right
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cmp #$52
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bne not_up
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jsr move_up
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clv
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bvc loop
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not_up
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cmp #$51
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bne loop
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jsr move_down
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clv
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bvc loop
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clv
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bvc loop
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read_key
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lda key_addr
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ldx #$0
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stx key_addr
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2019-04-25 18:43:04 +00:00
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rts
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2019-04-25 21:17:31 +00:00
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move_right
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2019-04-25 18:43:04 +00:00
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inc $00
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2019-04-25 21:17:31 +00:00
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jsr render_dot
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2019-04-25 18:43:04 +00:00
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rts
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2019-04-25 21:17:31 +00:00
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move_left
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dec $00
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jsr render_dot
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2019-04-25 18:43:04 +00:00
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rts
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2019-04-25 21:17:31 +00:00
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move_up
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lda $00
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sbc #$40
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sta $0
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jsr render_dot
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2019-04-25 18:43:04 +00:00
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rts
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2019-04-25 21:17:31 +00:00
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move_down
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lda $00
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adc #$3f
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sta $0
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jsr render_dot
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rts
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render_dot
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inc draw_colour_addr
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lda draw_colour_addr
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ldx $00
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sta draw_addr, x
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rts
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