pep8.org/css/table_of_contents.css

.toc {
  box-sizing: border-box;
  display: none;
  width: 290px;
  height: 100%;
  padding: .5em;
  position: absolute;
  overflow: auto;
}

.toc-header {
  font-size: 1.3em;
  margin: 0;
  padding: 0;
}

.toc-link {
    direction: ltr;
  display: block;
  text-decoration: none;
  margin: 0 0 .2em;
  padding: 0;
  line-height: 1.1;
  color: inherit;
}

.toc-link:hover, .toc-link:active, .toc-link.current {
  color: #1EAEDB;
}

.toc-link.h1 {
  font-size: 1em;
  line-height: 1.2em;
  margin: .8em 0;
}

.toc-link.h2 {
  margin-left: .5em;
  font-size: .95em;
  font-style: italic;
}

.toc-link.h2::before {
  content:  '•';
  margin-right: .5em;
  text-align: left;
}

.toc-link.h3 {
  margin-left: 1em;
  font-size: .9em;
  margin-bottom: 0.4em;
  margin-top: 0.4em;
}

.toc-link.h3::before {
  content:  '◦';
  margin-right: .5em;
  text-align: left;
}

@media(min-width: 1070px) {
  .container {
    width: 100%;
    max-width: 1050px;
  }
  .toc {
    display: block;
  }
  .toc + .nine.columns {
    margin-left: 350px;
    max-width: 700px;
  }
}