Pico W ten-second game with a tilt switch

# GAME: 10 seconds. Shake the tilt switch (GP16) to start a stopwatch,
# shake it again to stop. Stop it on exactly 10.00 seconds to win.
from machine import Pin
import time

DIGITS = [0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D, 0x7D, 0x07, 0x7F, 0x6F]
ds = Pin(18, Pin.OUT)
latch = Pin(19, Pin.OUT)
clock = Pin(20, Pin.OUT)
selects = [Pin(n, Pin.OUT, value=1) for n in (10, 11, 12, 13)]   # digit 1 to 4

def segments(byte):
    for i in range(7, -1, -1):
        ds.value((byte >> i) & 1)
        clock.value(1)
        clock.value(0)
    latch.value(1)
    latch.value(0)

def show(text):
    # text is four characters, digits or spaces, with an optional "." after
    # one of them. Each digit is lit for a moment in turn, fast enough
    # that the eye sees all four.
    cells = []
    for ch in text:
        if ch == "." and cells:
            cells[-1] |= 0x80
        else:
            cells.append(DIGITS[int(ch)] if ch.isdigit() else 0)
    for n, byte in enumerate(cells[-4:]):
        segments(byte)
        selects[n].value(0)
        time.sleep_ms(2)
        selects[n].value(1)

running = False
began = 0
elapsed = 0
shaken = False

def shake(pin):
    global shaken
    shaken = True

Pin(16, Pin.IN).irq(trigger=Pin.IRQ_RISING, handler=shake)
last = time.ticks_add(time.ticks_ms(), -1000)
print("shake to start")

while True:
    if shaken:
        shaken = False
        now = time.ticks_ms()
        if time.ticks_diff(now, last) > 300:      # one shake, not its bounces
            last = now
            if running:
                running = False
                elapsed = time.ticks_diff(now, began)
                print("stopped at %.2f s" % (elapsed / 1000))
                print("You win!" if elapsed // 10 == 1000 else "Try again")
            else:
                running = True
                began = now
                print("go")
    if running:
        elapsed = time.ticks_diff(time.ticks_ms(), began)
    hundredths = elapsed // 10 % 10000
    show("%02d.%02d" % (hundredths // 100, hundredths % 100))