rr_gamecenter.lua

gc.authenticate_local_user(function (error)
                               if (not error) then
                                   klog.info ("Game Center authentication OK!")
                                   rr_gc.user_authenticated = gc.local_user_id()
                                   -- uncomment the next line to reset GC achievements on launch
                                   -- gc.reset_achievements(function () print "achievements reset ok!" end)
                               else
                                   rr_gc.user_authenticated = false
                                   klog.warning("Game Center authentication failed: "..error)
                               end
                           end)