private void EnterMenu()
 {
     menuScreen.Fade(0f, 1f, () => {
         menuScreen.Activate();
         gameState = GameState.Menu;
     });
 }
 private void EnterRestartState()
 {
     if (gameState == GameState.Completed)
     {
         return;
     }
     if (gameState == GameState.Restart)
     {
         return;
     }
     gameState = GameState.Restart;
     restartScreen.Fade(0f, 1f, () => {
         restartScreen.Activate();
     });
 }