from machine import Pin , PWM
from time import ticks_ms, sleep_ms
buzzer = PWM(Pin(13))

start_time = ticks_ms() 

while True:
    elapsed_time = ticks_ms() - start_time
    if elapsed_time < 2000:
        buzzer.duty_u16(32768) # 50% duty cycle
        buzzer.freq(261) # C4
        sleep_ms(200)
        buzzer.duty_u16(0)
        sleep_ms(100)
    elif elapsed_time < 4000:
        buzzer.duty_u16(32768) # 50%
        buzzer.freq(329)   # E4
        sleep_ms(200)
        buzzer.duty_u16(0)
        sleep_ms(100)
    elif elapsed_time < 6000:
        buzzer.duty_u16(32768)
        buzzer.freq(392)  # g4
        sleep_ms(200)
        buzzer.duty_u16(0)
        sleep_ms(100)
    elif elapsed_time < 8000:
        buzzer.duty_u16(32768)
        buzzer.freq(440)   # a4
        sleep_ms(200)
        buzzer.duty_u16(0)
        sleep_ms(100)
    else:
        break