// United States of America
// http://www.crwflags.com/fotw/flags/us.html
@mixin flag-usa() {
  @include ratio(10 / 19);
  $unit: $width / 24700;
  $red: #ba0c2f;
  $blue: #012169;
  $white: #FFF;
  $stripe-size: percentage(1/13);
  $star-size: 800 * $unit;
  $star-margin-left: 1646 * $unit;
  $star-margin-top: 700 * $unit;
  $star-even-offset-left: 823 * $unit;
  $star-even-offset-top: 700 * $unit;
  $star-odd-offset-left: 1646 * $unit;
  $star-odd-offset-top: 1400 * $unit;
  $canton-width: 9876 * $unit;
  $canton-height: 7000 * $unit; 


  @include lines($red, $stripe-size,
                 $white, $stripe-size,
                 $red, $stripe-size,
                 $white, $stripe-size,
                 $red, $stripe-size,
                 $white, $stripe-size,
                 $red, $stripe-size,
                 $white, $stripe-size,
                 $red, $stripe-size,
                 $white, $stripe-size,
                 $red, $stripe-size,
                 $white, $stripe-size,
                 $red, $stripe-size);
  &:before {
    @include rectangle($blue, $canton-width, $canton-height);
  }
  &:after {
    @include symbol($UTF8_BLACK_STAR, transparent, $star-size);
    $shadows: ();
    @for $y from 0 to 9 {
      @for $x from 0 to 6 {
        $is_odd: ($y % 2 == 1);
        $is_last: ($x == 5);

        $offset-left: $star-even-offset-left;
        $offset-top: $star-even-offset-top;
        // Slightly move even rows on the right
        @if ($is_odd) {
          $offset-left: $star-odd-offset-left;
        }

        // Do not display the 6th star of odd lines
        @if (not ($is_odd and $is_last)) {
          $left: ($offset-left + ($x * $star-margin-left));
          $top: ($offset-top + ($y * $star-margin-top));
          $shadows: append($shadows, $left $top 0px $white, comma);
        }
      }
    }
    text-shadow: $shadows;
  }
};