.two-column-layout {
  display: flex;
}

.index-column {
  flex: 0 0 15%;
  padding: 20px;
  border-right: 1px solid #ddd;
  position: sticky; /* Make the column stick to the top */
  top: 80px; /* Height of the main navbar */
  /* To make the column scrollable, it needs a fixed height.
  We calculate this height to be 100% of the viewport height (100vh) minus the 75px taken up by the navbar.
  This makes the index column fill the available vertical space perfectly. */
  height: calc(100vh - 80px);
  /* If the content inside the index column is taller than its calculated height,
   a vertical scrollbar should appear for that column only. */
  overflow-y: auto;
}
.index-entries-container {
  display: block;
}
.index-column-entry {
  border-bottom: 1px solid #10ffff;
  display: block;
  padding-top: 8px;
  padding-bottom: 8px;
}

.content-column {
  flex: 0 0 85%;
  padding: 8px;
}