           "enter": {
                "x": { "scale": "x", "field": "x" },
                "width": { "scale": "x", "band": 1, "offset": -1 },
                "y": { "scale": "y", "field": "y0" },
                "y2": { "scale": "y", "field": "y1" },
                "fill": { "scale": "color", "field": "c" }
              },
              "update": {
                "fillOpacity": { "value": 1 }
              },
              "hover": {
                "fillOpacity": { "value": 0.5 }
              }
      