SCSS font-size mixin for using rems with fallback

_font-size.scss

// strip-unit function courtest of Karl Merkli http://css-tricks.com/snippets/css/less-mixin-for-rem-font-sizing/
@function strip-unit($num) {
	@return $num / ($num * 0 + 1);
}

// $size arg is the desired font size in pixels (e.g. @include font-size(16px);)
// Requires a $base-font-size variable be set and used like so:
//
// $base-font-size: 16px;
//
// // Later...
//
// html {
//     font-size: $base-font-size;
// }
@mixin font-size($size) {
	$raw-value: strip-unit($size);
	$raw-base-value: strip-unit($base-font-size);
	font-size: $raw-value + px;
	font-size: ($raw-value / $raw-base-value) + rem;
}