Pixel to REM Fallback Mixin

_rem-fallback.scss

// My modified version of Karl Merkli's rem mixin from http://css-tricks.com/snippets/css/less-mixin-for-rem-font-sizing/.

// Pass in a property name and the target pixel values and the mixin will spit out the pixel fallback version and the rem version.

@function strip-unit($num) {
  @return $num / ($num * 0 + 1);
}

@mixin rem-fallback($property, $values...) {
  $max: length($values);
  $pxValues: '';
  $remValues: '';

  @for $i from 1 through $max {
    $value: strip-unit(nth($values, $i));

    // If the value is '0' don't output the unit.
    @if $value == 0 {
      $pxValues: #{$pxValues + $value*1};
      $remValues: #{$remValues + $value/16};
    }

    // Else do output the unit.
    @else {
      $pxValues: #{$pxValues + $value*1}px;
      $remValues: #{$remValues + $value/16}rem;
    }

    @if $i < $max {
      $pxValues: #{$pxValues + " "};
      $remValues: #{$remValues + " "};
    }
  }

  #{$property}: $pxValues;
  #{$property}: $remValues;
}

//Example usage
h3 {
  display: inline-block;
  background-color: red;
  @include rem-fallback(padding, 16, 32, 48, 64);
}