import akka.actor._


  case class SetPartner(partner: ActorRef)
  case class Ball(volley: Int)

  class Player extends Actor {

    var partner = context.self

    def receive = {

      case SetPartner(p: ActorRef) =>
        partner = p

      case Ball(volley) =>
        Thread.sleep(500)

        if (volley <= 0) {
          println("Game over")
        } else {
          println (self.path.name + ": " + volley)
          partner ! Ball(volley-1)
        }
    }
  }

  object hello extends App{
    val system = ActorSystem("PingPongDemo")
    val ping = system.actorOf(Props[Player], "Ping")
    val pong = system.actorOf(Props[Player], "Pong")

    ping ! SetPartner(pong)
    pong ! SetPartner(ping)

    pong ! Ball(10)
  }