content: sub main()
      screen = createObject("roSGScreen")
      m.port = createObject("roMessagePort")
      screen.setMessagePort(m.port)
      screen.createScene("MainScene")
      screen.show()
      while(true)
          msg = wait(0, m.port)
          msgType = type(msg)
          if msgType = "roSGScreenEvent"
              if msg.IsScreenClosed() then return
          end if
      end while
  end sub