edx-platform/lms/static/sass/discussion/elements/_navigation.scss

.forum-nav {
  @include box-sizing(border-box);
  float: left;
  position: relative;
  width: 31%;
  border: 1px solid #aaa;
  border-radius: 3px;
}

// ------
// Header
// ------
.forum-nav-header {
  @include box-sizing(border-box);
  display: table;
  border-bottom: 1px solid $gray-l2;
  background-color: $gray-l3;
}

.forum-nav-browse {
  @include box-sizing(border-box);
  display: table-cell;
  vertical-align: middle;
  width: 50%;
  padding: ($baseline/4);

  &:hover, &:focus, &.is-active {
    background-color: $gray-l5;
  }

  .icon {
    @include font-size(14);
    margin-right: ($baseline/4);
  }
}

.forum-nav-browse-current {
  @include font-size(12);
}

.forum-nav-browse-drop-arrow {
  margin-left: ($baseline/4);
}

.forum-nav-search {
  @include box-sizing(border-box);
  display: table-cell;
  position: relative;
  vertical-align: middle;
  width: 50%;
  padding: ($baseline/4);
}

.forum-nav-search .icon {
  @include font-size(12);
  position: absolute;
  margin-top: -6px;
  top: 50%;
  right: ($baseline/4 + 1px + $baseline / 4); // Wrapper padding + border + input padding
}

.forum-nav-search-input {
  width: 100%;
}

// -----------
// Browse menu
// -----------
.forum-nav-browse-menu-wrapper {
  border-bottom: 1px solid $gray-l3;
  background: $gray-l5;
}

.forum-nav-browse-filter {
  position: relative;
  border-bottom: 1px solid $gray-l2;
  padding: ($baseline/4);
}

.forum-nav-browse-filter .icon {
  @include font-size(12);
  position: absolute;
  margin-top: -6px;
  top: 50%;
  right: ($baseline/4 + 1px + $baseline / 4); // Wrapper padding + border + input padding
}

.forum-nav-browse-filter-input {
  width: 100%;
}

.forum-nav-browse-menu {
  @include font-size(14);
  overflow-y: scroll;
  list-style: none;
}

.forum-nav-browse-submenu {
  padding-left: $baseline;
  list-style: none;
}

.forum-nav-browse-title {
  display: block;
  border-bottom: 1px solid $gray-l3;
  padding: ($baseline/2) ($baseline/2);

  &:hover, &:focus {
    background: $forum-color-active-thread;
  }
}

.forum-nav-browse-title .icon {
  margin-right: ($baseline/2);
}

// -------------------
// Sort and filter bar
// -------------------
.forum-nav-refine-bar {
  @include clearfix();
  @include font-size(11);
  border-bottom: 1px solid $gray-l3;
  background-color: $gray-l5;
  padding: ($baseline/4) ($baseline/2);
  color: $black;
}

%forum-nav-select {
  border: none;
  max-width: 100%;
  background-color: transparent;
  font: inherit;
}

.forum-nav-filter-cohort-control {
  @extend %forum-nav-select;
}

.forum-nav-sort {
  float: right;
}

.forum-nav-sort-control {
  @extend %forum-nav-select;
}

// -----------
// Thread list
// -----------
.forum-nav-thread-list {
  overflow-y: scroll;
  list-style: none;
}

.forum-nav-thread {
  border-bottom: 1px solid $gray-l3;
  background-color: $gray-l5;

  &.is-unread {
    background-color: $white;
  }
}

.forum-nav-thread-link {
  display: block;
  padding: ($baseline/4) ($baseline/2);

  &.is-active, &:hover, &:focus {
    background-color: $forum-color-active-thread;
  }
}

%forum-nav-thread-wrapper {
  display: inline-block;
  vertical-align: middle;
}

.forum-nav-thread-wrapper-1 {
  @extend %forum-nav-thread-wrapper;
  width: 70%;
}

.forum-nav-thread-wrapper-2 {
  @extend %forum-nav-thread-wrapper;
  width: 30%;
  text-align: right;
}

.forum-nav-thread-title {
  @extend %t-title7;
  display: block;
}

%forum-nav-thread-label {
  @extend %t-weight4;
  @include font-size(9);
  display: inline;
  margin-top: ($baseline/4);
  border: 1px solid;
  border-radius: 3px;
  padding: 1px 6px;
  text-transform: uppercase;
  white-space: nowrap;

  &:last-child {
    margin-right: 0;
  }

  .icon {
    margin-right: ($baseline/5);
  }

}

.forum-nav-thread-label-pinned {
  @extend %forum-nav-thread-label;
  border-color: $forum-color-pinned;
  color: $forum-color-pinned;
}

.forum-nav-thread-label-following {
  @extend %forum-nav-thread-label;
  border-color: $forum-color-following;
  color: $forum-color-following;
}

.forum-nav-thread-label-staff {
  @extend %forum-nav-thread-label;
  border-color: $forum-color-staff;
  color: $forum-color-staff;
}

.forum-nav-thread-label-community-ta {
  @extend %forum-nav-thread-label;
  border-color: $forum-color-community-ta;
  color: $forum-color-community-ta;
}

%forum-nav-thread-wrapper-2-content {
  @include font-size(11);
  display: inline-block;
  margin-right: ($baseline/4);
  text-align: center;
  color: $black;

  &:last-child {
    margin-right: 0;
  }
}

.forum-nav-thread-endorsed {
  @extend %forum-nav-thread-wrapper-2-content;
  color: $green-d1;
}

.forum-nav-thread-votes-count {
  @extend %forum-nav-thread-wrapper-2-content;
}

.forum-nav-thread-comments-count {
  @extend %forum-nav-thread-wrapper-2-content;
  @extend %t-weight4;
  position: relative;
  margin-left: ($baseline/4);
  margin-bottom: ($baseline/4); // Because tail is position: absolute
  border-radius: 2px;
  padding: ($baseline/10) ($baseline/5);
  min-width: 2em; // Fit most comment counts but allow expansion if necessary
  background-color: $gray-l3;

  // Speech bubble tail
  &:after {
    content: '';
    display: block;
    position: absolute;
    bottom: (-$baseline/4);
    right: ($baseline/4);
    width: 0;
    height: 0;
    border-style: solid;
    border-width: 0 ($baseline/4) ($baseline/4) 0;
    border-color: transparent $gray-l3 transparent transparent;
  }

  &.is-unread {
    background-color: $white;

    &:after {
      border-right-color: $white
    }
  }
}

.forum-nav-thread.is-unread .forum-nav-thread-comments-count {
  background-color: $blue;
  color: $white;

  &:after {
    border-right-color: $blue;
  }
}

.forum-nav-load-more {
  border-bottom: 1px solid $gray-l3;
  background-color: $gray-l5;
}

%forum-nav-load-more-content {
  display: block;
  padding: $baseline 0;
  text-align: center;
}

.forum-nav-load-more-link {
  @extend %forum-nav-load-more-content;
  color: $link-color;

  &:hover, &:focus {
    color: $link-color;
    background-color: $forum-color-active-thread;
  }
}

.forum-nav-loading {
  @extend %forum-nav-load-more-content;
}