from machine import Pin
from utime import sleep

led1 = Pin(0, Pin.OUT)
led2 = Pin(1, Pin.OUT)
led3 = Pin(2, Pin.OUT)
led4 = Pin(3, Pin.OUT)

while True:
    for i in range(16): 
        binary_value = bin(i)[2:].zfill(4)

       
        led1.value(int(binary_value[3]))
        led2.value(int(binary_value[2]))
        led3.value(int(binary_value[1]))
        led4.value(int(binary_value[0]))

        sleep(1)