content: sub main()
      m.screen = CreateObject("roSGScreen")
      m.port = CreateObject("roMessagePort")
      m.screen.setMessagePort(m.port)
      m.global = m.screen.getGlobalNode()
      m.global.addFields({
          "cart": []
      })
      m.scene = m.screen.CreateScene("MainScene")
      m.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