{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "width": 400,
  "height": 350,
  "padding": 10,
  "autosize": "pad",

  "config": {
    "legend": {
      "titleOrient": "left",
      "offset": 4,

      "symbolDirection": "horizontal",
      "symbolFillColor": "#4682b4",
      "symbolStrokeWidth": 0,
      "symbolOpacity": 1,
      "symbolType": "circle",

      "layout": {
        "right": {
          "direction": "vertical",
          "anchor": {"signal": "anchorRight"}
        },
        "bottom": {
          "margin": 2,
          "direction": "vertical",
          "anchor": "middle",
          "center": true
        },
        "top": {
          "margin": 2,
          "direction": "vertical",
          "anchor": "end"
        }
      }
    }
  },

  "signals": [
    {
      "name": "anchorRight", "value": "middle",
      "bind": {"input": "select", "options": ["start", "middle", "end"]}
    }
  ],

  "data": [
    {
      "name": "source",
      "url": "data/cars.json",
      "transform": [
        {
          "type": "filter",
          "expr": "datum.Horsepower != null && datum.Miles_per_Gallon != null && datum.Acceleration != null"
        }
      ]
    }
  ],

  "scales": [
    {
      "name": "x",
      "type": "linear",
      "round": true,
      "nice": true,
      "zero": true,
      "domain": {"data": "source", "field": "Horsepower"},
      "range": "width"
    },
    {
      "name": "y",
      "type": "linear",
      "round": true,
      "nice": true,
      "zero": true,
      "domain": {"data": "source", "field": "Miles_per_Gallon"},
      "range": "height"
    },
    {
      "name": "size",
      "type": "linear",
      "round": true,
      "nice": false,
      "zero": true,
      "domain": {"data": "source", "field": "Acceleration"},
      "range": [4, 361]
    }
  ],

  "axes": [
    {
      "scale": "x",
      "grid": true,
      "domain": false,
      "orient": "bottom",
      "tickCount": 5,
      "title": "Horsepower",
      "titleAnchor": "end",
      "titleBaseline": "bottom",
      "titleY": -5
    },
    {
      "scale": "y",
      "grid": true,
      "domain": false,
      "orient": "left",
      "titlePadding": 5,
      "title": "Miles_per_Gallon",
      "titleAlign": "left",
      "titleBaseline": "bottom",
      "titleAnchor": "end",
      "titleAngle": 90,
      "titleX": 5
    }
  ],

  "legends": [
    {
      "size": "size",
      "orient": "right",
      "title": "Acceleration",
      "direction": "vertical",
      "titleOrient": "top",
      "values": [1, 5, 10, 20]
    },
    {
      "size": "size",
      "orient": "bottom",
      "title": "Legend 1",
      "values": [0, 2, 5, 10, 12, 15, 18, 20]
    },
    {
      "size": "size",
      "orient": "bottom",
      "title": "Legend 2",
      "values": [0, 2, 5, 10, 15, 20]
    }
  ],

  "marks": [
    {
      "name": "marks",
      "type": "symbol",
      "from": {"data": "source"},
      "encode": {
        "enter": {
          "x": {"scale": "x", "field": "Horsepower"},
          "y": {"scale": "y", "field": "Miles_per_Gallon"},
          "size": {"scale": "size", "field": "Acceleration"},
          "shape": {"value": "circle"},
          "opacity": {"value": 0.25}
        },
        "update": {
          "fill": {"value": "#4682b4"}
        },
        "hover": {
          "fill": {"value": "firebrick"}
        }
      }
    }
  ]
}