{

  "title":{
    "text":"Test stacked bar charts",
    "style":"{font-size:16px;}"
  },

  "elements":[
    {
      "type":      "bar_stack",
      "keys": [
        {"colour":"#FFB900", "text": "Key 1", "font-size": 10},
        {"colour":"#ff00ff", "text": "Key 2", "font-size": 16},
        {"colour":"#FFB9F0", "text": "Key 3"},
        {"colour":"#FFB9F0", "font-size": 16},
        {"text": "Key 5", "font-size": 16}
      ],

      "values" :   [
                    [2.5,{"val":5}],
                    [{"val":2.5},{"val":5},{"val":2.5}],
                    null,
                    [{"val":5},{"val":5},{"val":2},{"val":2},{"val":2,"colour":"#ff00ff"},{"val":2},{"val":2}]
                   ]
    }
  ],

  "x_axis":{
    "max":4,
    "steps": 1,
    "labels": {
      "labels": ["January","February","March","April"]
    },
    "stroke": 12,
    "tick-height": 6
  },

  "y_axis":{
    "max": 20
  }
}