Android's 'screen pin' option lets you control how your phone is used

Parents who want to give their phone to their child to play a game or watch a movie can ensure that's all that can be done with the ‘screen pinning’ option on Android devices. — dpa

You want to share your smartphone with someone else for a bit so they can play a game or watch a film, but you also want to make sure they don't do anything else with it when you're not watching.

The solution, at least on Android, is the "screen pinning" function. To get there, head to Settings and pick "Security," then "Advanced" or "Other security settings", depending on what version you have.