3],
          "range": [0.15, 0.5, 0.8, 1.0]
        }
      ],

      "marks": [
        {
          "type": "rect",
          "from": { "data": "nodes" },
          "interactive": false,
          "encode": {
            "enter": {
              "fill": { "scale": "color", "field": "name" },
              "opacity": { "value": 0.2 }
            },
            "update": {
              "x": { "field": "x0" },
              "y": { "field": "y0" },
              "x2": { "field": "x1" },
              "y2": {