_rem.scss

$guss-rem-baseline: 10px !default;

// Transform a value into rem
// Assuming baseline is set to 10px on :root or html
@function rem($value, $baseline: $guss-rem-baseline) {
    @if $value == 0 { @return 0; } // 0rem -> 0
    @if type-of($value) == list {
        $result: ();
        @each $e in $value {
            $result: append($result, rem($e, $baseline));
        }
        @return $result;
    } @else {
        @return if(type-of($value) == number and unit($value) == px, $value / $baseline * 1rem, $value);
    }
}


// Output rem units with px fallback
// Expects $properties to be a Sass map
// Usage: http://sassmeister.com/gist/7451284
@mixin rem($properties) {
    @each $property, $value in $properties {
        @if (type-of($value) == number and $value != 0) {
            // Turn any value into pixels
            $value: if(unitless($value), $value * 1px, $value);
        }

        #{$property}: $value;
        #{$property}: rem($value);
    }
}