title: Do I need Google+ sign-in to use Google Play Game Services?
body: <p>I was trying to integrate a Google+ sign-in button into my app.  I kept getting this "Unknown error" that no one seems to have an answer too and its apparently an error that has been happening a lot since Google released this at their I/O recently.</p>
  
  <p><a href="https://stackoverflow.com/questions/17032860/google-sign-in-results-in-a-unknown-error-google-play-game-services/17033047?noredirect=1#17033047">My SO thread on "Unknown error" here.</a></p>
  
  <p>So my question is if this Google+ sign-in button even necessary for me to integrate Google Play Game Services (GPGS) into my app?  If I use a feature of the GPGS, do I have to let the users log into Google+?  Ultimately all I want is to use the leaderboard feature of the GPGS and couldn't care less if they are logged into Google+.</p>