このようなプログラムを、XcodeのPlaygroundで作りました
しかし、touchesBeganが動作しません
上手く行けば、「touched」と表示されるはずなのですが、表示されません

import UIKit
import SpriteKit
import PlaygroundSupport

class set: SKScene {
    //var Progress = 0
    //var button: SKNode? = nil

    func start() {
        let sceneWidth = 450.0
        let sceneHeight = 800.0
        //var ProcessSeed = 0
        let sceneView = SKView(frame: CGRect(x: 0.0, y: 0.0, width: sceneWidth, height: sceneHeight))
        PlaygroundPage.current.liveView = sceneView
        let back: SKScene = SKScene(size: CGSize(width: sceneWidth, height: sceneHeight))
        back.backgroundColor = UIColor.white
        sceneView.presentScene(back)

        let character = SKSpriteNode(imageNamed: "SobacchiStand.png")
        character.position = CGPoint(x: sceneWidth/2, y: sceneHeight/2)
        character.xScale = 0.5;
        character.yScale = 0.5;
        back.addChild(character)

        let button = SKSpriteNode(imageNamed: "Button.png")
        button.xScale = 0.1;
        button.yScale = 0.1;
        button.position = CGPoint(x: 400.0, y:100.0)
        button.zPosition = 1
        button.name = "button"
        back.addChild(button)

        button.isUserInteractionEnabled = true
        }
    func doit() {
        print("実行")
        print("されています")
    }

   /* override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        if let touch = touches.first as UITouch? {
            let location = touch.location(in: self)
            if self.atPoint(location).name == "button" {
                print("button tapped")
            }
        }
    }*/
    override func touchesBegan(_ touches: Set<UITouch>,with event: UIEvent?)   
{     //super.touchesBegan(touches, with: event)
        print("touched")
   }
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesEnded(touches, with: event)
       print("touchend")
    }
}

let first = set()
let second = first.start()
var Progress = 0

/*while Progress <= 100 {
    first
}*/

エラー自体は出ていない上、どのサイトを見ても、間違っている点が見当たらないのですが、どこか間違っているのでしょうか？