You can either play through connecting to your Facebook account, or choose to play with a Guest account. The only way to transfer your balance from one mobile device to another is by connecting both of them to Facebook. When you connect your device to Facebook, you will be presented with the option to merge your account. Tapping “Yes“ will complete the merge. Should you wish to do the same for a new device, please likewise tap “Yes“ to ensure that your progress is carried over.