html, body {
  margin: 0;
  padding: 0;
}

body {
  line-height: 1.5;
  color: rgb(55, 53, 47);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

.container {
  max-width: 900px;
  margin: 2em auto;
  padding-top: 45px;
}

.tree, .tree ul {
  list-style: none;
  padding-left: 20px;
}
.tree > li { padding-left: 0; }
.tree li { margin: 2px 0; }
.tree a {
  color: inherit;
  text-decoration: underline;
}
.tree a:hover {
  text-decoration: underline;
}
.tree details { margin: 0; }
.tree summary {
  cursor: pointer;
  padding: 1px 0;
}
.tree summary:hover {
  background: #f5f5f5;
}