     
     private var distanceLabel = UILabel()
     private var trackingStateLabel = UILabel()
-    private var startNode = SCNNode()
-    private var endNode = SCNNode()
+    private var startNode: SCNNode?
+    private var endNode: SCNNode?
     
     var dragOnInfinitePlanesEnabled = false
     

        super.didReceiveMemoryWarning()
        // Release any cached data, images, etc that aren't in use.
    }

    // MARK: - ARSCNViewDelegate
    
/*
    // Override to create and configure nodes for anchors added to the view's session.

        // Show statistics such as fps and timing information
        sceneView.showsStatistics = true
        
        // Adding tap gesture
        let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(ViewController.handleTapGesture))
        view.addGestureRecognizer(tapGestureRecognizer)
        
        distanceLabel.text = "Distance: ?"
        distanceLabel.textColor = .red
        distanceLabel.frame = CGRect(x: 5, y: 5, width: 150, height: 25)
        view.addSubview(distanceLabel)
        
        trackingStateLabel.frame = CGRect(x: 5, y: 35, width: 300, height: 25)
        view.addSubview(trackingStateLabel)
        
        setupFocusSquare()
    }
    
    override func viewWillAppear(_ animated: Bool) {
