<div id="chart"></div>
.c3 svg ,
.c3-legend-item {
  font-size: 15px;
}

.c3 path {
  stroke: #ccc;
  stroke-width:  2;
}

var chart = c3.generate({
    bindto: '#chart',
    data: {
      columns: [
        ['data1', 30, 200, 100, 400, 150, 250],
        ['data2', 50, 20, 10, 40, 15, 25]
      ]
    }
});

External CSS

  1. https://cdnjs.cloudflare.com/ajax/libs/c3/0.6.7/c3.css

External JavaScript

  1. https://d3js.org/d3.v5.min.js
  2. https://cdnjs.cloudflare.com/ajax/libs/c3/0.6.7/c3.js