from machine import Pin
from utime import sleep
from neopixel import NeoPixel

sleep(0.1)
led2=NeoPixel(Pin(20), 16) 
while 1:
    for j in range(16):
        for i in range(16):
            led2[i] = (255, 255, 255) # set the first pixel to white
        led2[j]=(255, 0, 0) 
        if j<15:
            led2[j+1]=(255, 0, 0) 
        else:
            led2[0]=(255, 0, 0) 
        led2.write()              # write data to all pixels
        sleep(0.3)