// list-separator polyfill by Hugo Giraudel (https://sass-compatibility.github.io/#list_separator_function)
@function em-separator($list) {
  @if function-exists("list-separator") == true {
    @return list-separator($list);
  }

  $test-list: ();
  @each $item in $list {
    $test-list: append($test-list, $item, space);
  }

  @return if($test-list == $list, space, comma);
}

@function em($values...) {
  $context: nth($values, length($values));
  $result: ();
  $separator: em-separator($values);

  @for $i from 1 through length($values) - 1 {
    $value: nth($values, $i);
    @if type-of($value) == "number" and unit($value) == "px" {
      $result: append($result, $value / $context * 1em, $separator);
    } @else if type-of($value) == "list" {
      $result: append($result, em(append($value, $context)...), $separator);
    } @else {
      $result: append($result, $value, $separator);
    }
  }

  @return if(length($result) == 1, nth($result, 1), $result);
}

@mixin em($properties, $context) {
  @each $property in map-keys($properties) {
    #{$property}: em(append(map-get($properties, $property), $context)...);
  }
}