@mixin border($color: null, $style: null, $width: null, $thin-width: false, $important: false)
  &
    border-color: $color if($important, !important, null)
    border-style: $style if($important, !important, null)
    border-width: $width if($important, !important, null)

  @if $thin-width
    &--border
      border-width: $thin-width
      box-shadow: none