angular-docs-cn/public/resources/css/module/_alert.scss

.alert {
  box-shadow: 0px 2px 5px rgba($coal, 0.3);
  border-width: 2px;
  border-style: solid;
  padding: $unit ($unit * 2);
  line-height: $unit * 4;
  font-size: 14px;
  border-radius: 4px;
  color: $steel;
  margin-bottom: $unit * 3;

  &.is-critical {
    border-color: $cardinal;
    background: $peach;
  }

  &.is-important {
    border-color: $citrus;
    background: $sand;
  }

  &.is-helpful {
    border-color: $blueberry;
    background: $light;
  }
}