moving_point.asm

; Made by Renato Araujo, 2023
; renatorraraujo@gmail.com
; gh: renatoexpert

JSR init
JSR loop

init: 
    LDA #$11
    STA $00
    LDA #$02
    STA $01
    RTS 

loop: 
    JSR clear
    JSR getkey
    JSR draw
    JSR sleep
    JMP loop 

clear: ; clear current position
    LDY #$00
    LDA #$00
    STA ($00),y
    RTS 

getkey: 
    CLC 
    LDA $ff 
    CMP #$77
    BEQ upkey
    CMP #$64 
    BEQ rightkey
    CMP #$73
    BEQ downkey
    CMP #$61
    BEQ leftkey
    RTS 

rightkey:
    INC $00
    RTS 

leftkey: 
    DEC $00
    RTS 

upkey:
    LDA $00
    SBC #$20
    STA $00
    RTS 

downkey: 
    LDA $00
    ADC #$1F
    STA $00
    RTS 

draw:
    LDY  #$00
    LDA $01
    STA ($00),y
    RTS 

sleep:
    LDX #$00
    LDY #$00
    JSR sleepcycle 
    RTS 

sleepcycle:    
    NOP
    NOP
    DEX 
    BNE sleepcycle 
    DEY 
    BNE sleepcycle  
    RTS