Special handling of keyword arguments

keyword-arguments.css

#please-wait {
  background: url(/images/logo.png);
  position: absolute;
  top: 3em;
  right: 0;
  bottom: 3em;
  left: 0;
}

keyword-arguments.scss

@mixin wallpaper($image, $top: 0, $right: 0, $bottom: 0, $left: 0) {
  background: $image;
  position: absolute;
  top: $top;
  right: $right;
  bottom: $bottom;
  left: $left;
}

@mixin logo($offsets...) {
  @include wallpaper(url(/images/logo.png), $offsets...);
}

#please-wait {
  @include logo($top: 3em, $bottom: 3em);
}