     
     @IBAction func didTapScreen(_ sender: UITapGestureRecognizer) { // fire bullet in direction camera is facing
         
+        // Play torpedo sound when bullet is launched
+        
         do
         {
             let MusicURL = Bundle.main.path(forResource: "torpedo", ofType: "mp3")

                print(error.description)
            }
            
            print("Hit ship!")
            self.removeNodeWithAnimation(contact.nodeB, explosion: false) // remove the bullet
            self.userScore += 1

    }
    
    func removeNodeWithAnimation(_ node: SCNNode, explosion: Bool) {
        
        // Play collision sound for all collisions (bullet-bullet, etc.)
        
        do
        {
            let MusicURL = Bundle.main.path(forResource: "collision", ofType: "mp3")
            try Player = AVAudioPlayer(contentsOf: NSURL (fileURLWithPath:MusicURL!) as URL)
            Player.prepareToPlay()
            Player.play()
        }
        catch let error as NSError {
            print(error.description)
        }
        
        if explosion {
            
            // Play explosion sound for bullet-ship collisions
            
            do
            {
