body {
  font-family: Arial, sans-serif;
  margin: 20px;
}

#graph {
  border: 1px solid #ccc;
  width: 800px;
  height: 600px;
}

.links line {
  stroke: #999;
  stroke-opacity: 0.6;
}

.nodes circle {
  stroke: #fff;
  stroke-width: 1.5px;
}