d3/examples/spline/spline.css

body {
  font: 13px sans-serif;
}

circle, .line {
  fill: none;
  stroke: steelblue;
  stroke-width: 1.5px;
}

circle {
  fill: #fff;
  fill-opacity: .2;
  cursor: move;
}

circle.selected {
  fill: #ff7f0e;
  stroke: #ff7f0e;
}