@@ -1,7 +1,7 @@
 APP_PLATFORM := android-22
 #APP_ABI := all
-APP_ABI := armeabi-v7a
-#APP_STL := arm64-v8a
+#APP_ABI := armeabi-v7a
+APP_STL := arm64-v8a
 
 APP_STL := c++_static
 
 
@@ -105,10 +105,9 @@ void Engine::InitGooglePlayGameServices() {
  *
  */
 void Engine::OnAuthActionStarted(gpg::AuthOperation op) {
-  if (!initialized_resources_) return;
+  startup_mutex_.lock();
   ndk_helper::JNIHelper::GetInstance()->RunOnUiThread([this, op]() {
     EnableUI(false);
-    authorizing_ = true;
     if (op == gpg::AuthOperation::SIGN_IN) {
       LOGI("Signing in to GPG");
       status_text_->SetAttribute("Text", "Signing In...");
@@ -136,16 +135,14 @@ void Engine::OnAuthActionFinished(gpg::AuthOperation op,
     });
   }
 
-  if (!initialized_resources_) return;
-
   ndk_helper::JNIHelper::GetInstance()->RunOnUiThread([this, status]() {
     EnableUI(true);
-    authorizing_ = false;
     button_sign_in_->SetAttribute(
         "Text", gpg::IsSuccess(status) ? "Sign Out" : "Sign In");
 
     status_text_->SetAttribute(
         "Text", gpg::IsSuccess(status) ? "Signed In" : "Signed Out");
+    startup_mutex_.unlock();
   });
 }
 
@@ -560,14 +557,12 @@ void Engine::LeaveGame() {
  * invoking jui_helper functions to create java UIs
  */
 void Engine::InitUI() {
-  // Show toast with app label
-
   // The window initialization
   jui_helper::JUIWindow::Init(app_->activity, JUIHELPER_CLASS_NAME);
 
+  // Show toast with app label
   ndk_helper::JNIHelper::GetInstance()->RunOnUiThread([]() {
     if(NULL == jui_helper::JUIWindow::GetInstance()->GetContext()) {
-	LOGE("====JUIWindow::Context is NULL, not showing Toast");
         return;
     }
     jui_helper::JUIToast toast(
@@ -580,9 +575,6 @@ void Engine::InitUI() {
   // UIs.
   //
 
-  // The window initialization
-  //  jui_helper::JUIWindow::Init(app_->activity, JUIHELPER_CLASS_NAME);
-
   //
   // Buttons
   //
@@ -655,7 +647,6 @@ void Engine::InitUI() {
   // Init play game services
   InitGooglePlayGameServices();
 
-  if (authorizing_) EnableUI(false);
   return;
 }
 
 
@@ -147,13 +147,13 @@ class Engine : public gpg::IRealTimeEventListener {
                             // in OnRoomStatusChanged()
   int32_t score_counter_;   // Score counter of local player
   bool playing_;            // Am I playing a game?
-  bool authorizing_;        // Am I signing in to gpg service?
   std::string self_id_;     // Local player's ID
   double start_time_;       // Game start time
 
   // synchronization primitive to synchronize
   // UIThread, Timer thread and gpg callback thread
   mutable std::mutex mutex_;
+  mutable std::mutex startup_mutex_;
 
   // Renderer of a teapot
   TeapotRenderer renderer_;
 
@@ -23,7 +23,6 @@
 Engine::Engine()
     : initialized_resources_(false),
       has_focus_(false),
-      authorizing_(false),
       app_(nullptr),
       dialog_(nullptr),
       textViewFPS_(nullptr),
@@ -61,14 +60,12 @@ void Engine::UnloadResources() { renderer_.Unload(); }
  */
 int Engine::InitDisplay(const int32_t cmd) {
   if (!initialized_resources_) {
-    while(authorizing_) {
-      std::chrono::milliseconds d(100);
-      std::this_thread::sleep_for(d);
-    }
+    startup_mutex_.lock();
     gl_context_->Init(app_->window);
     InitUI();
     LoadResources();
     initialized_resources_ = true;
+    startup_mutex_.unlock();
   } else {
     // initialize OpenGL ES and EGL
     if (EGL_SUCCESS != gl_context_->Resume(app_->window)) {