styles.css

.selected-option {
  border-style: solid;
  border-width: 3px;
  border-color: red;
}

.monospace {
  font-family: monospace;
}

table, th, td {
  border: 1px solid black;
  border-collapse: collapse;
}

.node {
  cursor: pointer;
}

.node:hover {
  stroke: #000;
  stroke-width: 1.5px;
}

.node--leaf {
  fill: white;
}

.label {
  font: 11px "Helvetica Neue", Helvetica, Arial, sans-serif;
  text-anchor: middle;
  text-shadow: 0 1px 0 #fff, 1px 0 0 #fff, -1px 0 0 #fff, 0 -1px 0 #fff;
}

.label,
.node--root,
.node--leaf {
  pointer-events: none;
}

text {
  font: 10px sans-serif;
}

tspan:last-child {
  font-size: 9px;
  fill-opacity: 0.8;
}

.node rect {
  shape-rendering: crispEdges;
}

.node--hover rect {
  stroke: #000;
}