It took a lot to set up on spectators phone to prepare and it’s not safe…
At any moment they
can check their phone if they are skeptical.
2-NFC it doesn’t work on I phone x or some android
phones and require the permission or NFC reader on menu.
3-if spectators turn over the phone
they can understand this is App so you need even to black the twist button on ios.
4- date
prediction (too many digits appear on the calculator and it seems unrealistic)
