application-4.js

window.requestAnimationFrame(function () {
   ...
  localGame = new GameManager(socket, false, 4, KeyboardInputManager, HTMLActuator, LocalStorageManager);
  
  // Add this socket lisetner
  socket.on('player-number', function (playerNumber) {
    if (playerNumber == 1) {
      waitingPlayerTwo(true); // Show waiting message
      
      // On 2nd player connect, start the game
      socket.on('player-connect', function() {
        waitingPlayerTwo(false); // Hide waiting message
        startGame();
      });
    } else { // Immediately start the game if we're player two
      startGame();
    }
  });