// Focus state mixin
@mixin focus-outline(
  $width: $theme-focus-width,
  $style: $theme-focus-style,
  $color: $theme-focus-color,
  $offset: $theme-focus-offset
) {
  $width: if($width == null, $theme-focus-width, $width);
  $style: if($style == null, $theme-focus-style, $style);
  $color: if($color == null, $theme-focus-color, $color);
  $offset: if($offset == null, $theme-focus-offset, $offset);
  outline: units($width) $style color($color);
  outline-offset: units($offset);
}