Wsrtjtyk

I am making a game with sprite kit in xcode and i want let the game finish when the player touch the monster, do you know how to use categorymask?

here is part of the code :

import SpriteKit
import GameplayKit
import CoreMotion

class GameScene: SKScene, SKPhysicsContactDelegate {

var player : SKSpriteNode!

var playerCategory : UInt32 = 0x1 << 0

var gameTimer2 : Timer!

var possiblealien = ["alien", "alien2", "alien3"]

let alienCategory : UInt32 = 0x1 << 1



override func didMove(to view: SKView) {





    player = SKSpriteNode (imageNamed: "player")

    player.position = CGPoint (x: self.frame.size.width / 2 - 500 , y: 

    player.size.height / 2 - 560)

    player.size = CGSize(width: player.size.width * 6 ,

                         height: player.size.height * 6)

    self.addChild(player)

    player.zPosition = 2



    self.physicsWorld.gravity = CGVector (dx: 0 , dy: 0 )

    self.physicsWorld.contactDelegate = self

    player.physicsBody?.contactTestBitMask = playerCategory

    player.physicsBody? = SKPhysicsBody(rectangleOf: player.size)

    player.physicsBody?.isDynamic = true

    player.physicsBody?.categoryBitMask = monsterCategory

    player.physicsBody?.collisionBitMask = 0





    gameTimer2 = Timer.scheduledTimer(timeInterval: 5, target: self, selector: #selector(addalien), userInfo: nil, repeats: true)

     motionManager.accelerometerUpdateInterval = 0.2

     motionManager.startAccelerometerUpdates(to: OperationQueue.current!) { ( data: CMAccelerometerData?, error:Error?)in



     if let accelerometerData = data {

     let acceleration = accelerometerData.acceleration

     self.xAcceleration = CGFloat(acceleration.x) * 0.65 + self.xAcceleration * 0.25

     }

    }

@objc func addalien () {

possiblealien = GKRandomSource.sharedRandom().arrayByShufflingObjects(in: possiblealien) as! [String]



let alien = SKSpriteNode(imageNamed: possiblealien[0])



let randomalienposition = GKRandomDistribution(lowestValue: -480, highestValue:  +800 )



let position = CGFloat(randomalienposition.nextInt())



alien.position = CGPoint (x: position - 200 , y: self.frame.size.height * 0.5 + alien.size.height)



alien.physicsBody = SKPhysicsBody(rectangleOf: alien.size)

alien.physicsBody?.isDynamic = true



alien.physicsBody?.categoryBitMask = alienCategory

alien.physicsBody?.contactTestBitMask = playerCategory

alien.physicsBody?.collisionBitMask = 0

alien.zPosition = 2

alien.size = CGSize(width: alien.size.width * 1 ,

                      height: alien.size.height * 1)

self.addChild(alien)



let animationduration:TimeInterval = 6

var actionArray = [SKAction]()



actionArray.append(SKAction.move(to: CGPoint(x: position, y: -1000 ),duration: animationduration))

actionArray.append(SKAction.removeFromParent())



alien.run(SKAction.sequence(actionArray))

}