//
        //  GameViewController.swift
        //  HitTheTree
        //
        //  Created by Christopher Anderson on 6/25/18.
        //  Copyright © 2018 Christopher Anderson. All rights reserved.
        //
        import UIKit
        import QuartzCore
        import SceneKit

        class GameViewController: UIViewController {

            override func viewDidLoad() {
                super.viewDidLoad()

                // create a new scene
                let scene = SCNScene(named: "art.scnassets/ship.scn")!

                // create and add a camera to the scene
                let cameraNode = SCNNode()
                cameraNode.camera = SCNCamera()
                scene.rootNode.addChildNode(cameraNode)

                // place the camera
                cameraNode.position = SCNVector3(x: 0, y: 0, z: 15)

                // create and add a light to the scene
                let lightNode = SCNNode()
                lightNode.light = SCNLight()
                lightNode.light!.type = .omni
                lightNode.position = SCNVector3(x: 0, y: 10, z: 10)
                scene.rootNode.addChildNode(lightNode)

                // create and add an ambient light to the scene
                let ambientLightNode = SCNNode()
                ambientLightNode.light = SCNLight()
                ambientLightNode.light!.type = .ambient
                ambientLightNode.light!.color = UIColor.darkGray
                scene.rootNode.addChildNode(ambientLightNode)

                // retrieve the ship node
                let ship = scene.rootNode.childNode(withName: "ship", recursively: true)!

                // animate the 3d object
                ship.runAction(SCNAction.repeatForever(SCNAction.rotateBy(x: 0, y: 2, z: 0, duration: 1)))

                // retrieve the SCNView
                let scnView = self.view as! SCNView

                // set the scene to the view
                scnView.scene = scene

                // allows the user to manipulate the camera
                scnView.allowsCameraControl = true

                // show statistics such as fps and timing information
                scnView.showsStatistics = true

                // configure the view
                scnView.backgroundColor = UIColor.black

                // add a tap gesture recognizer
                let tapGesture = UITapGestureRecognizer(target: self, action: #selector(handleTap(_:)))
                scnView.addGestureRecognizer(tapGesture)
            }

            @objc
            func handleTap(_ gestureRecognize: UIGestureRecognizer) {
                // retrieve the SCNView
                let scnView = self.view as! SCNView

                // check what nodes are tapped
                let p = gestureRecognize.location(in: scnView)
                let hitResults = scnView.hitTest(p, options: [:])
                // check that we clicked on at least one object
                if hitResults.count > 0 {
                    // retrieved the first clicked object
                    let result = hitResults[0]

                    // get its material
                    let material = result.node.geometry!.firstMaterial!

                    // highlight it
                    SCNTransaction.begin()
                    SCNTransaction.animationDuration = 0.5

                    // on completion - unhighlight
                    SCNTransaction.completionBlock = {
                        SCNTransaction.begin()
                        SCNTransaction.animationDuration = 0.5

                        material.emission.contents = UIColor.black

                        SCNTransaction.commit()
                    }

                    material.emission.contents = UIColor.red

                    SCNTransaction.commit()
                }
            }

            override var shouldAutorotate: Bool {
                return true
            }

            override var prefersStatusBarHidden: Bool {
                return true
            }

            override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
                if UIDevice.current.userInterfaceIdiom == .phone {
                    return .allButUpsideDown
                } else {
                    return .all
                }
            }

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

        }