hugo-theme-minima/assets/sass/toc.scss

details.toc {
  position: sticky;
  top: 0;
  background-color: var(--back);
  transition: .5s all;
}

details.toc summary {
  position: relative;
  width: fit-content;
  cursor: pointer;
  background-color: var(--back);
  transition: .5s all;
}

details.toc div {
  background-color: var(--back);
  transition: .5s all;
}

details.toc ul {
  list-style-type: none;
  padding-inline-start: 1em;
  margin: 0;
}

details.toc ul > li {
  margin: 1em 0;
}

details.toc-bar,
details.toc-lines {
  & summary {
    padding-right: 0.5em;
    list-style: none;
  }
  & summary::-webkit-details-marker {
    display: none;
  }
  & div {
    padding-top: 1em;
  }
}

details.toc-bar {
  top: 1rem;
  background-color: transparent;

  & div {
    top: -1em;
    padding-top: 2em;
    background-color: var(--back);
  }

  & summary {
    --toc-bar-ht: 4px;
    --toc-bar-wd: 8%;
    width: var(--toc-bar-wd);
    height: var(--toc-bar-ht);
    margin-left: calc(50% - var(--toc-bar-wd) / 2);
    border-radius: calc(var(--toc-bar-ht) / 2);
    background-color: var(--text);
    box-shadow: var(--back) 0 0 8px 8px;
  }
}

details.toc-default,
details.toc-lines {
  & summary {
    padding-top: 1em;
  }
}

details.toc-lines {
  & summary::before {
    content: "≡";
    font-size: 1.5em;
    position: relative;
    top: 0;
  }
}

details[open] {
  &.toc-lines summary::before {
    content: "×";
    font-size: 1.7em;
    top: -4px;
  }
}