@mixin breakpoint( $size, $width-type: min-width) {
  @if type-of( $size ) != 'string' {
    @error 'NSW-DS Breakpoint mixin accepts only strings';
  }

  @if $size != 'xs' and $size != 'sm' and $size != 'md' and $size != 'lg' and $size != 'xl' {
    @error 'NSW-DS Breakpoint mixin allows the following breakpoint sizes xs, sm, md, lg';
  } @else {
    $px-size: map-get($breakpoints, $size);
    $em-size: em($px-size);

    @media ($width-type: $em-size) {
      @content;
    }
  }
}