Sign in with Apple is a feature on iOS devices that allows you to save your progress in the game in a similar way to using a Facebook login does.

Using Sign in with Apple is not necessary to play the game, but does allow you to save level progress and keep this in sync across other devices that you might play on that also support the Sign in with Apple feature.

For more information on the Sign in with Apple feature or for help with signing in, please follow this link: https://support.apple.com/en-us/HT210318

Please note that Sign in with Apple may not be available on Android devices, and will not sync progress with these devices, unless this option is available on a non-iOS version of the app.