About the screen transition using Segue in SKScene in Xcode(Swift)

class ViewControllerB:UIViewController{
    override func viewDidAppear(_animated:Bool){

        super.viewDidLoad()
        letscene=GameScene()
        let view=self.view as!SKView

        view.showsFPS=true
        view.showsNodeCount=true

        scene.size=view.frame.size

        view.presentScene(scene)
    }   
}

class GameScene:SKScene, SKPhysicsContactDelegate{

    varbowl —SKSpriteNode?

    var timer —Timer?

    var lowestShape —SKShapeNode?

    varscore = 0
    varscoreLabel—SKLabelNode?
    varscoreList= [100, 200, 300, 500, 800, 1000, 1500]
    var viewController:UIViewController?

    override func DidMove (to view:SKView) {

        self.physicsWorld.gravity=CGVector (dx: 0.0, dy: -2.0)
        self.physicsWorld.contactDelegate=self

        let background=SKSpriteNode(imageNamed: "background")
        background.position = CGPoint (x:self.size.width*0.5, y:self.size.height*0.5)
        background.size=self.size
        self.addChild(background)

        let lowestShape=SKShapeNode(rectOf:CGSize(width:self.size.width*3, height:10))
        lowestShape.position = CGPoint (x:self.size.width*0.5, y:-10)

        letphysicsBody = SKPhysicsBody (rectangleOf:lowestShape.frame.size)
        physicsBody.isDynamic=false
        physicsBody.contactTestBitMask = 0x1<<1
        lowestShape.physicsBody=physicsBody

        self.addChild(lowestShape)
        self.lowestShape =lowestShape

        let bowlTexture=SKTexture(imageName: "bowl")
        let bowl = SKSpriteNode (texture: bowlTexture)
        bowl.position = CGPoint (x:self.size.width*0.5, y:100)
        bowl.size = CGSize (width: bowlTexture.size().width*0.5, height: bowlTexture.size().height*0.5)
        bowl.physicsBody = SKPhysicsBody (texture: bowlTexture, size: bowl.size)
        bowl.physicsBody?isDynamic=false
        self.bowl = bowl
        self.addChild(bowl)

        varscoreLabel=SKLabelNode(fontNamed: "Helvetica")
        scoreLabel.position = CGPoint (x:self.size.width*0.92, y:self.size.height*0.78)
        scoreLabel.text=" "0"
        scoreLabel.fontSize=32
        scoreLabel.horizontalAlignmentMode=SKLabelHorizontalAlignmentMode.right
        scoreLabel.fontColor=UIColor.green
        self.addChild(scoreLabel)
        self.scoreLabel=scoreLabel

        self.fallNagoyaSpecialty()

        self.timer = Timer.scheduledTimer (timeInterval:3, target:self, selector:#selector (fallNagoyoSpecialty), userInfo:nil, repeat:true)
    }

    @objc func fallNagoyaSpecialty(){
        let index = Int(arc4 random_uniform(7))
        let texture=SKTexture(imageNamed:"\"(index)")
        let sprite=SKSpriteNode(texture:texture)
        sprite.position = CGPoint (x:self.size.width*0.5, y:self.size.height)
        sprite.size = CGSize (width:texture.size().width*0.5, height:texture.size().height*0.5)
        sprite.physicsBody=SKPhysicsBody(texture:texture, size:sprite.size)
        sprite.physicsBody?.contactTestBitMask = 0x1<<1

        self.addChild(sprite)

        self.score+=self.scoreList [index]
        self.scoreLabel?.text=" \\(self.score)"
    }

    override functouchesBegan(_touches:Set<UITouch>, with event:UIEvent?){
        iflet touch=touches.first{
            let location = touch.location(in:self)
            let action = SKAction.move (to: CGPoint (x: location.x, y:100), duration: 0.2)
            self.bowl?.run(action)
        }
    }

    override functouchesMoved(_touches:Set<UITouch>, with event:UIEvent?) {
        iflet touch=touches.first{
            let location = touch.location(in:self)
            let action = SKAction.move (to: CGPoint (x: location.x, y:100), duration: 0.2)
            self.bowl?.run(action)
        }
    }

    func DidBegin(_contact:SKPhysicsContact){
        if contact.bodyA.node==self.lowestShape||contact.bodyB.node==self.lowestShape{
            let sprite=SKSpriteNode(imageNamed: "gameover")
            sprite.position = CGPoint (x:self.size.width*0.5, y:self.size.height*0.5)
            self.addChild(sprite)

            self.isPaused=true
            self.timer?.invalidate()
            haveScore()
            let myButton=UIButton()
            myButton.frame = CGRect (x:0, y:0, width:200, height:40)
            myButton.backgroundColor=UIColor.red
            myButton.setTitle("Next", for:UIControl.State.normal)
            myButton.setTitleColor (UICol.white, for:UIControl.State.normal)
            myButton.layer.cornerRadius=20.0
            myButton.layer.position=CGPoint (x:self.view!.frame.width/2, y:200.0)
            myButton.addTarget(self, action:#selector(self.next(sender:))), for:.touchUpInside)
            self.view!.addSubview(myButton)     
        }
    }
    funhaveScore(){
        let appDelegate=UIApplication.shared.delegate as!AppDelegate
        appDelegate.message=score
    }

    @objc func next (sender: UIButton) {

        self.viewController?.performSegue(withIdentifier: "toFinish", sender:nil)
    }

}