from microbit import*

x=2
while True:
  if button_b.was_pressed():
    display.set_pixel(x,2,0)
    x=x+1
    if x>4:
      x=4
    display.set_pixel(x,2,9)
    sleep(200)
  if button_a.was_pressed():
    display.set_pixel(x,2,0)
    x=x-1
    if x<0:
      x=0
      
    display.set_pixel(x,2,9)
    sleep(200)