hacks-guide-minimal-mistakes-theme/assets/_scss/_toc.scss

/* ==========================================================================
   TABLE OF CONTENTS
   ========================================================================== */

.toc {
  padding: 0 0 1em;
  font-family: $sans-serif-narrow;
  color: $gray;
  text-transform: uppercase;
  letter-spacing: 1px;
  background-color: #fff;
  @include breakpoint($large) {
    position: absolute;
    top: 0;
    right: calc(50% - (0.5 * #{$large}) + 1em); // 50% - 1/2 of wrapper's max-width + wrapper padding
    width: $right-sidebar-width;
    padding-left: 2em;
  }
  @include breakpoint($x-large) {
    right: calc(50% - (0.5 * #{$x-large}) + 1em); // 50% - 1/2 of wrapper's max-width + wrapper padding
  }
}

.toc__title {
  margin: 0;
  padding: 10px 20px;
  font-family: $sans-serif-narrow;
  font-size: 16px;
  color: #fff;
  border: 1px solid $border-color;
  border-top-left-radius: $border-radius;
  border-top-right-radius: $border-radius;
  background: $gray;
}

.toc__menu {
  margin: 0;
  padding: 0;
  width: 100%;
  list-style: none;
  border: 1px solid $border-color;
  border-top: none;
  border-bottom-right-radius: $border-radius;
  border-bottom-left-radius: $border-radius;
  a {
    display: block;
    padding: 10px 20px;
    color: $gray;
    font-size: 11px;
    font-weight: bold;
    line-height: 1.5;
    border-left: 0.5em solid $gray;
    border-bottom: 1px solid $border-color;
    &:hover {
      color: #000;
      border-left: 0.5em solid $info-color;
      background: mix(#fff, $info-color, 90%);
    }
  }
  li ul > li a {
    font-weight: normal;
    border-left: 0.5em solid mix(#fff, $gray, 25%);
  }
  li ul > li > ul > li a {
    border-left: 0.5em solid mix(#fff, $gray, 50%);
  }
  // hide sub sub links on small screens
  li > ul li {
    display: none;
    @include breakpoint($large) {
      display: block;
    }
  }
}