h1 {
margin-bottom: 2em; font-size: 28px;
}
h2 {
margin-bottom: 0.5em; font-size: 24px;
}
graph {
width: 960px; height: 500px; border: 1px solid #ccc; margin-bottom: 2em;
}
.node {
stroke: #fff; stroke-width: 1.5px;
}
.link {
stroke: #999; stroke-opacity: .6; stroke-width: 1px;
}