.archive-tree-block details,
.archive-tree-block .archive-tree-year,
.archive-tree-block details > summary.archive-tree-year {
  margin-top: 0;
  margin-bottom: 0;
  padding-top: 0;
  padding-bottom: 0;
}
.archive-tree-year {
  font-weight: bold;
}
.archive-tree-month {
  margin-left: 2em;
  padding-left: 0.5em;
  border-left: 2px solid #ccc;
  display: block;
}