Unity -

Google Login

Download and install Android Studio as it is the easiest way to install and maintain Android tools

Install > Custom > Select Everything

When the IDE starts, go to Configure... > SDK Manager at lower right.

Inside, press Launch Standalone SDK Manager at lower left.

Scroll down at the bottom and install Google Play services.

Go to Google Developer Console.

Create developer account, it costs 25$.

Create new app: Game Services > Add New Game > *give it a name*.

Linked Apps > Android and add your package name defined in Unity player settings.

Run keytool -list -v -keystore $HOME/.android/debug.keystore -alias androiddebugkey -storepass android -keypass android

Copy Certificate fingerprints > SHA1 to the web page.

Import Google Play Services to your Unity project. Download the repo and there is asset package in current-build/.

Window > Google Play Games > Setup > Android Setup