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Sleep as Android has a CAPTCHA mode that prevents you from shutting off the alarm without some form of verification, like solving a math problem or scanning an NFC tag or bar code.

I struggle mightily with mornings and have been late to work countless times because I can unconsciously shut off my alarm. But with the CAPTCHA mode I can’t shut the alarm off without physically getting out of bed, carrying my phone into the other room, and scanning an NFC tag. It’s been a life saver.

I haven’t seen such a feature in any other alarm app.

It’s most likely water. The two main chemical products of fuel combustion are carbon dioxide and water vapor. The vapor condenses and drips out of the exhaust.