@function px2em($px, $base-font-size: 16px) {
  @if (unitless($px)) {
    @warn "Assuming #{$px} to be in pixels, attempting to convert it into pixels for you";
    @return px2em($px + 0px);
  } @else if (unit($px) == em) {
    @return $px;
  }
  @return ($px / $base-font-size) * 1em;
}