@function deep-map-merge($map, $maps...) {
  $last: nth($maps, -1);
  $deep: $last == true;
  $max: if($deep, length($maps) - 1, length($maps));

  // Loop through all maps in $maps...
  @for $i from 1 through $max {
    // Store current map
    $current: nth($maps, $i);

    // If not in deep mode, simply merge current map with map
    @if not $deep {
      $map: map-merge($map, $current);
    } @else {
      // If in deep mode, loop through all tuples in current map
      @each $key, $value in $current {
        // If value is a nested map and same key from map is a nested map as well
        @if type-of($value) == "map" and type-of(map-get($map, $key)) == "map" {
          // Recursive extend
          $value: deep-map-merge(map-get($map, $key), $value, true);
        }

        // Merge current tuple with map
        $map: map-merge(
          $map,
          (
            $key: $value
          )
        );
      }
    }
  }

  @return $map;
}