svg {
  background: white;
}

.node {
  fill: lightgray;
  stroke: gray;
  stroke-width: 2px;
}
.link {
  stroke: black;
  opacity: 0.1;
}
.label {
  text-anchor: middle;
  font-size: 16px;
  fill: #444;
  font-weight: bold;
  font-family: sans-serif;
}