Thanks for your interest for the game! You don't have to need any log-in to start and play the game. But if you want to log-in to buy in-app-purchase items or have a persistent game data across platforms (the game supports cross-platform play where you can sync your data across platforms like Google Play, Apple App Store, Steam(PC/ MAC), etc. , you would need to log-in with your Google ID. And don't forget to pre-register the game to get some cool stuff on Jan 15th of the official release! Hope we can see each other inside the game on Jan 15th! :)