@mixin side-radius($direction, $radius) {
  @if ($direction == left) {
    border-top-left-radius: $radius;
    border-bottom-left-radius: $radius;
  } @else if($direction == right) {
    border-top-right-radius: $radius;
    border-bottom-right-radius: $radius;
  } @else if($direction == top) {
    border-top-left-radius: $radius;
    border-top-right-radius: $radius;
  } @else if($direction == bottom) {
    border-bottom-left-radius: $radius;
    border-bottom-right-radius: $radius;
  }
}