// rem fallback - credits: http://zerosixthree.se/
  
  @function calculateRem($size) {
    $remSize: $size / 16px;
    @return $remSize * 1rem;
  }
  
  @mixin font-size($size) {
    font-size: $size;
    font-size: calculateRem($size);
  }
  
  // border radius
  
  @mixin border-radius($radius:.25em) {
    border-radius: $radius;
  }