@IBAction func startTapped(_ sender: Any) {
    let request = GKMatchRequest()
    request.maxPlayers = 2
    request.minPlayers = 1

    let mmvc = GKMatchmakerViewController(matchRequest: request)
    mmvc?.matchmakerDelegate = self
    present(mmvc!, animated: true, completion: nil)
}

extension HomeVC: GKGameCenterControllerDelegate
{

    func authenticatePlayer()
    {
        //CALLED ON VIEWDIDAPPEAR
        let localPlayer = GKLocalPlayer.localPlayer()

        localPlayer.authenticateHandler = {
            (view, error) in
            if view != nil
            {
                self.present(view!, animated: true, completion: nil)
            } else {
                print("AUTHENTICATED!")
                print(GKLocalPlayer.localPlayer().isAuthenticated)
            }
        }
    }
func gameCenterViewControllerDidFinish(_ gameCenterViewController: GKGameCenterViewController) {
        gameCenterViewController.dismiss(animated: true, completion: nil)
    }
}

extension HomeVC: GKMatchmakerViewControllerDelegate {
    func matchmakerViewControllerWasCancelled(_ viewController: GKMatchmakerViewController) {
       print("match was cancelled")
        viewController.dismiss(animated: true, completion: nil)
    }

    func matchmakerViewController(_ viewController: GKMatchmakerViewController, didFailWithError error: Error) {
        print("didFailwithError: (error.localizedDescription)")
    }

    func matchmakerViewController(_ viewController: GKMatchmakerViewController, didFind match: GKMatch) {

        print("Match found, ID: (match.description)")
        let gameScreenVC = self.storyboard?.instantiateViewController(withIdentifier: "mainGame") as! ViewController
        gameScreenVC.providesPresentationContextTransitionStyle = true
        gameScreenVC.definesPresentationContext = true
        gameScreenVC.modalPresentationStyle = UIModalPresentationStyle.fullScreen
        gameScreenVC.modalTransitionStyle = UIModalTransitionStyle.crossDissolve
        match.delegate = gameScreenVC

        self.present(gameScreenVC, animated: true, completion: nil)

    }
}