Defaults for margins on mixin square-image.
@import 'sizing-utils';
-@mixin square-image($size, $margin-top, $margin-right, $margin-bottom, $margin-left) {
+@mixin square-image($size, $margin-top: 0, $margin-right: 0, $margin-bottom: 0, $margin-left: 0) {
won-square-image {
display: block;
