discourse/app/assets/stylesheets/common/select-kit/combo-box.scss

.select-kit {
  &.combo-box {
    min-width: auto;
    .select-kit-body {
      width: 100%;
      min-width: 150px;
      border-radius: 0;
      box-shadow: shadow("dropdown");    
    }

    .select-kit-row {
      margin: 0;
      min-height: 1px;
      padding: 6px 10px;
      &.no-content {
        font-weight: normal;
      }
    }

    .select-kit-filter {
      line-height: $line-height-medium;
      padding: $input-padding;
      border-top: 1px solid dark-light-diff($primary, $secondary, 90%, -60%);
      border-bottom: 1px solid dark-light-diff($primary, $secondary, 90%, -60%);

      .filter-input {
        margin-right: 5px;
        width: auto;        
      }
    }
    
    .select-kit-header {
      background: $secondary;
      border: 1px solid $primary-medium;
      padding: $input-padding;
      font-weight: 500;
      font-size: $font-0;
      line-height: $line-height-large;

      &.is-focused {
        border: 1px solid $tertiary;
        box-shadow: shadow("focus");
      }
    }

    .select-kit-collection {
      display: flex;
      flex-direction: column;
      padding: 0;
      min-width: 100px;
      max-height: 200px;
      max-width: 32em;

      .collection-header {
        a {
          white-space: nowrap;
          color: $primary;
          line-height: $line-height-medium;
          font-weight: bold;
          display: block;
          padding: 6px 10px;
          color: $tertiary;

          &:hover {
            text-decoration: underline;
          }
        }
      }
    }

    &.is-disabled {
      .select-kit-header {
        background: #e9e9e9;
        border-color: #ddd;
      }
    }

    &.is-highlighted {
      .select-kit-header {
        border: 1px solid $tertiary;
        box-shadow: shadow("focus");
      }
    }

    &.is-expanded {
      .select-kit-wrapper {
        display: block;
        border: 1px solid $tertiary;
        box-shadow: shadow("focus");
      }

      .select-kit-body {
        border-radius: 0 0 3px 3px ;
      }
    }

    &.is-expanded.is-above {
      .select-kit-header {
        border-radius: 0 0 3px 3px;
      }

      .select-kit-body {
        border-radius: 3px 3px 0 0;
      }
    }

    &.tag-drop, &.group-dropdown {
      min-width: auto;
      .select-kit-row {
        font-weight: bold;
      }

      &.is-expanded .select-kit-wrapper, .select-kit-wrapper {
        display: none;
      }
    }
  }
}