Settings
Put your phone flat on a stable, dry surface. Lower into a push-up and gently touch the coloured area with your nose. Keep touching until it turns green and beeps. Lift your nose to count one rep. If you lift too early, it doesn't count. Try it with a finger first.
Some noses won't register on capacitive screens. Touch detection depends on your phone. This is a training game, not a form or safety monitor.
The seed
Had this silly idea,
You open an app / web page.
You do a push up.
Your nose has to touch the screen for a moment and when it changes colour or beeps you lift the push up.
Ie to make sure you are not using momentum to go back up.
Can the camera calculate how close a nose / face is to the screen?
The simplest is just rely on touch.
Thoughts.
So here’s the touch version. A little pause at the bottom, with your nose in charge of the timer.