notifications-admin/app/assets/stylesheets/components/textbox.scss

.textbox-highlight {

  $tag-background: rgba($light-blue, 0.6);

  &-wrapper {
    position: relative;
  }

  &-textbox {
    resize: none;
    z-index: 20;
    background: none;
  }

  &-textbox,
  &-background,
  &-foreground,
  &-mask {
    font-size: 19px;
    display: block;
    box-sizing: border-box;
    position: relative;
    margin: 0;
    padding: 4px;
    overflow: hidden;
    line-height: 1.6;
  }

  &-background {
    position: absolute;
    top: 0;
    left: 0;
    pointer-events: none;
    color: transparent;
    white-space: pre-wrap;
    overflow-wrap: break-word;
    word-wrap: break-word;
    border: 2px solid transparent;
    padding-bottom: $gutter-half;
    z-index: 10;

    .placeholder,
    .placeholder-conditional {
      color: transparent;
    }

  }

}

.textbox-help-link {
  margin: 10px 0 0 0;
}

.textbox-right-aligned {
  text-align: right;
}

.extra-tracking .form-control {
  @include core-19($tabular-numbers: true);
  padding-left: 5px;
  letter-spacing: 0.04em;
}

.textbox-colour-preview {
  @include media(desktop) {
    width: 38px;
    height: 38px;
    margin-left: 5px;
    border-radius: 50%;
    box-shadow: inset 0 0 0 1px rgba($black, 0.2);
    display: inline-block;
    vertical-align: top;
    transition: background 0.3s ease-out;
  }
}