from machine import Pin
# from time import sleep

led_pin = Pin(15, Pin.OUT)
button_pin = Pin(21, Pin.IN, Pin.PULL_DOWN)
print("Here we go.... press button again and again")
while True:
    while button_pin.value() == 0:
        pass
    led_pin.value(1-led_pin.value())
    while button_pin.value() == 1:
        pass