GameScene

import SpriteKit
import GameplayKit
import SwiftUI

class GameScene: SKScene, SKPhysicsContactDelegate, ObservableObject {  

    @Published var gameScore = 0
        override func didMove(to view: SKView) {
        backgroundColor = .yellow
        physicsBody = SKPhysicsBody(edgeLoopFrom: frame)
        ball()
     //   addScore()
    }
    func ball() {
           let ball = SKShapeNode(circleOfRadius: 50)
           ball.position = CGPoint(x: 100, y: 100)
           ball.fillColor = .blue
           self.addChild(ball)
       }

    let removeLabel = SKAction.sequence([SKAction.fadeIn(withDuration: 0.3),
    SKAction.wait(forDuration: 0.8), SKAction.fadeOut(withDuration: 0.3)])

    override func sceneDidLoad() {
        super.sceneDidLoad()
    }
   func addScore(){
        if gameScore < 10 {
            gameScore += 2          
        } else {
            gameScore += 4         
        }
    }    
}

/////////////
GameScene2

import SpriteKit
import GameplayKit

class GameScene2: SKScene {
    override func didMove(to view: SKView) {
        backgroundColor = .blue
        physicsBody = SKPhysicsBody(edgeLoopFrom: frame)
    }
    override func touchesBegan(_ touches: Set, with event: UIEvent?) {
        guard let touch = touches.first else { return }
        let location = touch.location(in: self)
        let box = SKSpriteNode(color: SKColor.red, size: CGSize(width: 40, height: 40))
        box.position = location
        box.physicsBody = SKPhysicsBody(rectangleOf: CGSize(width: 40, height: 40))
        addChild(box)
    }
}
/////////////////////
ContentView

import SwiftUI
import SpriteKit

struct ContentView: View {
@State var switcher = false
    @StateObject var gameScene: GameScene = GameScene() // <<: Here 3

var scene: SKScene {
    let scene = GameScene()
       scene.size = CGSize(width: 216, height: 216)
       scene.scaleMode = .fill
    //    scene.backgroundColor = .yellow
       return scene
}
var scene2: SKScene {
    let scene2 = GameScene2()
       scene2.size = CGSize(width: 216, height: 216)
       scene2.scaleMode = .fill
       return scene2
}

var body: some View {    
 //   Text("Score: \(gameScene.gameScore)") // <<: Here 4
      //       .onTapGesture {
     //            gameScene.addScore()  // <<: Here 5
    //         }
    Button(action: {
        gameScene.addScore()
         }, label: {
             Text("Score: \(gameScene.gameScore)")
         })
  if switcher {
    SpriteView(scene: scene)
        .frame(width: 256, height: 256)
        .ignoresSafeArea()
        .background(Color.red)
        .onAppear {
          scene2.isPaused = true
        }
        .onDisappear {
          scene2.isPaused = false
        }
        
  } else {
    SpriteView(scene: scene2)
        .frame(width: 256, height: 256)
        .ignoresSafeArea()
        .background(Color.blue)
        .onAppear {
          scene.isPaused = true      
        }
        .onDisappear {
          scene.isPaused = false
        }  
  }
  Button {
    withAnimation(.easeInOut(duration: 1.0)) {
      switcher.toggle()
    }
  } label: {
    Text("SceneMove")
  }
}
}