Overleaf/services/web/frontend/stylesheets/app/editor/left-menu.less

#left-menu {
  position: absolute;
  width: @left-menu-width;
  padding: (@line-height-computed / 2);
  top: 0;
  bottom: 0;
  background-color: #f4f4f4;
  z-index: 100;
  overflow-y: auto;
  overflow-x: hidden;
  -webkit-transition: left ease-in-out @left-menu-animation-duration;
  transition: left ease-in-out @left-menu-animation-duration;
  font-size: 14px;
  left: -@left-menu-width;

  &.shown {
    left: 0;
  }

  h4 {
    font-family: @font-family-sans-serif;
    font-weight: 400;
    font-size: 1rem;
    margin: (@line-height-computed / 2) 0;
    padding-bottom: (@line-height-computed / 4);
    color: @neutral-70;
    border-bottom: 1px solid @gray-lighter;
  }

  > h4:first-child {
    margin-top: 0;
  }

  ul.nav {
    .left-menu-button {
      cursor: pointer;
      padding: (@line-height-computed / 4);
      font-weight: 700;
      color: @link-color;
      display: flex;
      align-items: center;
      width: 100%;
      background-color: inherit;
      border: none;

      i {
        margin-right: @margin-sm;
        color: @gray;
      }

      &:hover,
      &:active {
        background-color: @link-color;
        color: white;

        i {
          color: white;
        }
      }
    }

    a {
      cursor: pointer;
      &:hover,
      &:active,
      &:focus {
        background-color: @link-color;
        color: white;
        i {
          color: white;
        }
      }
      i {
        color: @gray;
      }
      padding: (@line-height-computed / 4);
      font-weight: 700;
    }
    .link-disabled {
      color: @gray-light;
    }
  }

  > ul.nav:last-child {
    margin-bottom: @line-height-computed / 2;
  }

  ul.nav-downloads {
    li {
      display: inline-block;
      text-align: center;
      width: 100px;
      a {
        color: @gray-dark;
      }
      i {
        margin: (@line-height-computed / 4) 0;
      }
    }
  }

  form.settings {
    label {
      font-weight: normal;
      color: @gray-dark;
      flex: 1 0 50%;
      margin-bottom: 0;
      margin-top: 9px;
      padding-right: 5px;
      white-space: nowrap;
    }
    button,
    select {
      width: 50%;
      margin: 9px 0;
    }
    .form-controls {
      clear: both;
      padding: 0 9px;
      display: flex;
      flex-wrap: wrap;
      align-items: baseline;
      justify-content: flex-end;
      border-bottom: solid 1px rgba(0, 0, 0, 0.07);
      &:first-child {
        margin-top: -9px;
      }
      &:last-child {
        border-bottom: 0;
      }
      &:hover {
        background-color: @link-color;
        // select.form-control {
        // 	color: white;
        // }
        label,
        i.fa {
          color: white;
        }
      }
      &:after {
        content: '';
        display: table;
        clear: both;
      }
    }
  }

  .left-menu-setting-position {
    position: relative;

    .left-menu-setting {
      margin-top: 0 !important;
    }

    .left-menu-setting-icon {
      position: absolute;
      right: 65%;
      top: 25%;
    }
  }

  .left-menu-setting {
    padding: 0 9px;
    display: flex;
    flex-wrap: wrap;
    align-items: baseline;
    justify-content: flex-end;
    border-bottom: solid 1px rgba(0, 0, 0, 0.07);
    margin-bottom: 0;

    &:first-child {
      margin-top: -9px;
    }

    &:last-child {
      border-bottom: 0;
    }

    &:hover,
    &:focus-within {
      background-color: @link-color;

      label {
        color: @white;
      }
    }

    select.form-control {
      height: 23px;
      padding: 1px @padding-xs;
      font-size: inherit;

      &:hover {
        background-color: @ol-blue-gray-1;
      }
    }
  }
}

#left-menu-mask {
  .full-size;
  opacity: 0.4;
  background-color: #999;
  z-index: 99;
  transition: opacity 0.5s;
}

// Make the Bootstrap Modal behavior as a left sidebar
#left-menu-modal {
  opacity: 1;
  overflow-y: hidden;
  padding-left: 0 !important; // bootstrap modal may randomly give padding-left when zooming in / out in chrome
  .modal-dialog {
    height: 100%;
    margin: 0;
    width: @left-menu-width;
  }

  .modal-content {
    position: initial;
  }
  &.modal.fade .modal-dialog {
    left: -@left-menu-width;
    transition: left ease-in-out @left-menu-animation-duration;
    -webkit-transition: left ease-in-out @left-menu-animation-duration;
    transform: translate(0, 0);
  }
  &.modal.in .modal-dialog {
    left: 0;
    transform: translate(0, 0);
  }
}
// Don't disable backdrop that allows closing the Modal when clicking outside of it,
// But match its background color with the original mask background color.
.left-menu-modal-backdrop {
  background-color: transparent;
}