Id</a> on the circular shape.
  Note that we move the other port-related properties, such as the port spots, to that object too.
</p>
<pre class="lang-js" id="singlePort"><code>
  diagram.nodeTemplate =
    new go.Node("Vertical")
      .add(
        new go.Shape("Ellipse",
          { width: 30, height: 30, fill: "green",
            portId: "",  // now the Shape is the port, not the whole Node
            fromSpot: go.Spot.Right,  // port properties go on the port!
            toSpot: go.Spot.Left
       