Ensuring that your progress has been saved is important if you've just started the game. To make sure your game gets saved, you'll need to link your guest account to an email address, Google Play, or Facebook.
Linking your account to an email address
The game will link your account immediately.
Linking your account to Facebook
The game will link your account immediately.
Linking your account to Google Play
If you haven't used the selected Google account with the game before, the linking process will take place immediately.