import time
import board
import digitalio

poorten = [board.GP18, board.GP19, board.GP20, board.GP21]

leds = [digitalio.DigitalInOut(poort) for poort in poorten]

for led in leds:
    led.direction = digitalio.Direction.OUTPUT

while True:
    for led in leds:
        led.value = True
        time.sleep(0.2)
        led.value = False
        time.sleep(0.2)