from machine import Pin, PWM
from time import tick_ms, sleep_ms
buzzer=PWM(Pin(5))
start_time=tick_ms
while True:
    elapsed_ms=ticks_ms()-start_time
    if elapsed_ms<2000:
        buzzer.duty_u16(32768)
        buzzer.freq(261)
        sleep_ms(200)
        buzzer.duty_u16(0)
        sleep_ms(100)
    elif elapsed_ms<4000:
        buzzer.duty_u16(32768)
        buzzer.freq(329)
        sleep_ms(200)
        buzzer.duty_u16(0)
        sleep_ms(100)
    elif if elapsed_ms<6000:
        buzzer.duty_u16(32768)
        buzzer.freq(392)
        sleep_ms(200)
        buzzer.duty_u16(0)
        sleep_ms(100)
    elif elapsed_ms<8000:
        buzzer.duty_u16(32768)
        buzzer.freq(440)
        sleep_ms(200)
        buzzer.duty_u16(0)
        sleep_ms(100)
    else:
        buzzer.duty_u16(0)
        break: