from machine import Pin
import time

# Initialize all 3 traffic light LEDs as OUTPUT pins
red_led = Pin(15, Pin.OUT)
yellow_led = Pin(14, Pin.OUT)
green_led = Pin(13, Pin.OUT)

while True:
    # --- GREEN LIGHT ---
    green_led.value(1)
    yellow_led.value(0)
    red_led.value(0)
    time.sleep(3)       
    
    # --- YELLOW LIGHT ---
    green_led.value(0)
    yellow_led.value(1)
    red_led.value(0)
    time.sleep(1)       
    
    # --- RED LIGHT ---
    green_led.value(0)
    yellow_led.value(0)
    red_led.value(1)    
    time.sleep(3)