Time for action – starting and restarting the game

Let's add the logic to start and restart the game.

1. Let's write the implementation for resetGame:

   void GameLayer::resetGame(void) {
       _score = 0;
       _energy = 100;
       
       //reset timers and "speeds"
       _meteorInterval = 2.5;
       _meteorTimer = _meteorInterval * 0.99f;
       _meteorSpeed = 10;//in seconds to reach ground
       _healthInterval = 20;
       _healthTimer = 0;
       _healthSpeed = 15;//in seconds to reach ground
       
       _difficultyInterval = 60;
       _difficultyTimer = 0;
       
       _running = true;
       
       //reset labels
       _energyDisplay->setString(std::to_string((int) _energy) + "%");
       _scoreDisplay->setString(std::to_string((int) _score));
   }

2. Next, add the implementation of stopGame:

   void GameLayer::stopGame() {
       
       _running = false;
       
       //stop all actions currently running
       int i;
       int count = (int) _fallingObjects.size();
       
       for (i = count-1; i >= 0; i--) {
           auto sprite = _fallingObjects...