How to force close on your iPhone, iPad, or iPod touch

Closing and relaunching the app can resolve common cosmetic or one-off errors and refresh the game view.

iPhone 8 or earlier:

1. Double-click the Home button to show your most recently used apps. 
2. Swipe right or left to find the app that you want to close.  
3. Swipe up on the app's preview to close the app. 

iPhone X:

1. From the Home screen, swipe up and pause.
2. Firmly touch and hold the app, then tap . You can also swipe up to close the app as soon as you see .

For further details, please visit this Apple Support article.