Trying to remove black fill under lines in billboard.js line chart

Question

I am using the same example line chart shown here. However, I have black fill under the lines on my chart. How do I remove the black fill from under the lines. In the documentation under LineChartOptions there it only shows two configurable options, HidePoints and LinePoint. Here is my example. The same thing happens to my time series chart. Thank you.

var lineChart = bb.generate({
  data: {
    columns: [
    ["data1", 30, 200, 100, 400, 150, 250],
    ["data2", 50, 20, 10, 40, 15, 25]
    ],
    type: "line", // for ESM specify as: line()
  },
  bindto: "#lineChart"
});

Answer 1

Adding fill: none to the bb-chart-lines class should do the trick.

Add this to your CSS:

.bb-chart-lines {
  fill: none;
}

Link to Codepen