src/css/extensions/toc.css

@media screen and (min-width: 1025px) {
  .article-aside {
    display: block;
    position: fixed;
    top: 130px;
    right: 0;
    font-size: 0.9em;
    border-left: dotted 1px #e1e1e1;
    width: 16rem;
    margin-right: 2rem;
  }

  #article-toc {
    padding-left: 0;
    margin-right: 2rem;
  }

  .article-aside.hidden {
    display: none;
  }

  .doc {
    float: left;
    width: calc(100% - 22rem);
  }
}

.tocify {
  position: fixed;
}

.tocify ul,
.tocify li {
  background: transparent;
  list-style: none;
  margin: 0;
  padding: 0;
  border: none;
  line-height: 30px;
}

li.tocify-item.ui-state-default > a {
  font-weight: bolder;
}

.tocify-subheader {
  padding-left: 10px;
}

.tocify-subheader .tocify-subheader {
  padding-left: 20px;
  display: none;
}

.tocify-subheader .tocify-subheader .tocify-subheader {
  padding-left: 30px;
  display: none;
}

.-narrow aside.toc,
.-toc aside.toc {
  display: none;
}

@media screen and (min-width: 1025px) {
  .-narrow .doc {
    width: 95%;
  }
}

.-narrow .doc {
  max-width: 95%;
}

aside.toc #article-toc {
  padding-left: 20px;
  color: var(--color-causeway-blue);
  border: var(--color-causeway-purple) dashed;
  border-width: 0 0 0 0.1rem;
  -o-border-image: linear-gradient(var(--color-causeway-purple), var(--color-causeway-cyan)) 0 0 0 100%;
  border-image: -webkit-gradient(linear, left top, left bottom, from(var(--color-causeway-cyan))), to(var(--color-causeway-cyan)) 0 0 0 100%;
  border-image: linear-gradient(var(--color-causeway-cyan), var(--color-causeway-cyan)) 0 0 0 100%;
  margin-bottom: 1.5rem;
}

.toc-title {
  color: var(--color-causeway-purple);
}

aside.toc ul.tocify-subheader {
  margin-left: 20px;
}