text: 
   src="https://www.gstatic.com/firebasejs/4.7.0/firebase.js"
  
    // Initialize Firebase
    var config = {
      apiKey: "AIzaSyD8VBEaP3iGSU-VH6Sfj2DOLzCIzrH6H14",
      authDomain: "tictactoe-hk.firebaseapp.com",
      databaseURL: "https://tictactoe-hk.firebaseio.com",
      projectId: "tictactoe-hk",
      storageBucket: "tictactoe-hk.appspot.com",
      messagingSenderId: "450353938851"
    };
    firebase.initializeApp(config);
  