Restart game or move on

Alright. So. When I'm trying to do is restart the game if the ball touches a "danger" (Just a Sprite node thats a rectangle). How do I do that? I have no idea where to start with it. I have them both with physics bodies.

I want the ball to reset to the starting position that I defined in startGame()

ballPlayer.physicsBody?.isDynamic = true Thats where I give ballPlayer (The ball) a dynamic physics body. I don't know what else I should put there.

The rectangle is defined using the gameScene.sks storyboard.

import SpriteKit
import GameplayKit

class GameScene: SKScene {
    var ballPlayer = SKSpriteNode()

    override func didMove(to view: SKView) {

        ballPlayer = self.childNode(withName: "ballPlayer") as! SKSpriteNode
        ballPlayer.physicsBody?.isDynamic = true

        let border = SKPhysicsBody(edgeLoopFrom: self.frame)

        border.friction = 0
        border.restitution = 1

        self.physicsBody = border

        startGame()

        addSwipeGestureReconizers()
    }

    func addSwipeGestureReconizers() {
        let gestureDirections: [UISwipeGestureRecognizer.Direction] = [.right, .left, .up, .down]
        for gestureDirection in gestureDirections {
            let gestureReconzier = UISwipeGestureRecognizer(target: self, action: #selector(handleSwipe))
            gestureReconzier.direction = gestureDirection
            self.view?.addGestureRecognizer(gestureReconzier)
        }
    }

    func startGame() {
        ballPlayer.position = CGPoint(x: 0, y: 550)
    }

    @objc func handleSwipe(gesture: UIGestureRecognizer) {
        if let gesture = gesture as? UISwipeGestureRecognizer {
            switch gesture.direction {
            case .up:
                ballPlayer.physicsBody?.applyImpulse(CGVector(dx: 0, dy: 0))
                ballPlayer.physicsBody?.applyImpulse(CGVector(dx: 0, dy: 110))
                print("Swiped up")
            case .down:
                ballPlayer.physicsBody?.applyImpulse(CGVector(dx: 0, dy: 0))
                ballPlayer.physicsBody?.applyImpulse(CGVector(dx: 0, dy: -110))
                print("Swiped down")
            case .right:
                ballPlayer.physicsBody?.applyImpulse(CGVector(dx: 0, dy: 0))
                ballPlayer.physicsBody?.applyImpulse(CGVector(dx: 110, dy: 0))
                print("Swiped right")
            case .left:
                ballPlayer.physicsBody?.applyImpulse(CGVector(dx: 0, dy: 0))
                ballPlayer.physicsBody?.applyImpulse(CGVector(dx: -110, dy: 0))
                print("Swiped left")
            default:
                print("No such gesture")
            }
        }

    }
    override func update(_ currentTime: TimeInterval) {
        // Called before each frame is rendered
    }
}