from machine import Pin
import time
import neopixel

LED_PIN = 8
NUM_LEDS = 12

np = neopixel.NeoPixel(Pin(LED_PIN), NUM_LEDS)

# --- Helper functions -------------------------------------------------

def clear():
    """Turn off all LEDs."""
    np.fill((0, 0, 0))
    np.write()

def set_pixels(indices, color):
    """Set multiple LEDs to the same colour."""
    for i in indices:
        np[i] = color
    np.write()

# --- Traffic light colours --------------------------------------------

RED     = (255, 0, 0)
AMBER   = (100, 25, 0)
GREEN   = (0, 255, 0)

# --- Main loop ---------------------------------------------------------

while True:
    # Red
    clear()
    set_pixels([0, 1], RED)
    time.sleep(3)

    # Red + Amber
    set_pixels([4, 5], AMBER)
    time.sleep(2)

    # Green
    clear()
    set_pixels([8, 9], GREEN)
    time.sleep(3)

    # Amber
    clear()
    set_pixels([4, 5], AMBER)
    time.sleep(1)