When playing the game through your mobile device you are able to choose from the 3 following options of how to enter your game.
1.Play

Pressing the Play button instantly throws you into the Adventures of our beloved Diggy. The game is connected only to your phone, which means, that you are not able to enter it through any other device.
Losing your phone, or making a settings reset (factory reset) may result in your lost progress.
2. Facebook

Pressing the Facebook button will start a new adventure, which will be connected to the Facebook profile you are currently logged into. You will be able to play your game on whatever device using just your Facebook.
If you had an unconnected game on your phone, and you´ve pressed the Facebook button - this window may appear

Please, make sure to choose the progress with the highest progression as choosing either will connect your game to a Facebook profile, but you can also start from the beginning when choosing incorrectly.
3. E-mail

You are able to sign into the game through this third option. You are able to use your already existing credentials from the Pixel Federation Portal.
If you haven´t signed up on the Portal yet, this message will appear :

To be able to Sign Up visit the Pixel Federation Portal, and create a new E-Mail login.
You can find the article on how to create a new login here