@if $font-size {
  html {
    font-size: $font-size;
  }
}

body {
  line-height: $line-height;
}

@function font-size-from-ratio($ratio) {
  $numerator: nth($ratio, 1);
  $denumerator: nth($ratio, 2);
  @return calc(1em * (#{$numerator} / #{$denumerator}));
}

@mixin header($ratio) {
  $numerator: nth($ratio, 1);
  $denumerator: nth($ratio, 2);
  font-size: font-size-from-ratio($ratio);
  $leading-multiplier: ceil($numerator / $denumerator);
  line-height: calc(#{$leading-multiplier} * #{$leading-height});
}

$double-great-primer-ratio: 36, 12;
$double-pica-ratio: 24, 12;
$double-small-pica-ratio: 21, 12;
$great-primer-ratio: 18, 12;
$english-ratio: 14, 12;
$pica-ratio: 12, 12;
$small-pica-ratio: 11, 12;
$long-primer-ratio: 10, 12;
$bourgeois-ratio: 9, 12;
$brevier-ratio: 8, 12;
$minion-ratio: 7, 12;
$nonpareil-ratio: 6, 12;

$double-great-primer: font-size-from-ratio($double-great-primer-ratio);
$double-pica: font-size-from-ratio($double-pica-ratio);
$double-small-pica: font-size-from-ratio($double-small-pica-ratio);
$great-primer: font-size-from-ratio($great-primer-ratio);
$english: font-size-from-ratio($english-ratio);
$pica: font-size-from-ratio($pica-ratio);
$small-pica: font-size-from-ratio($small-pica-ratio);
$long-primer: font-size-from-ratio($long-primer-ratio);
$bourgeois: font-size-from-ratio($bourgeois-ratio);
$brevier: font-size-from-ratio($brevier-ratio);
$minion: font-size-from-ratio($minion-ratio);
$nonpareil: font-size-from-ratio($nonpareil-ratio);

h1 {
  @include header($double-great-primer-ratio);
}

h2 {
  @include header($double-pica-ratio);
}

h3 {
  @include header($double-small-pica-ratio);
}

h4 {
  @include header($great-primer-ratio);
}

h5 {
  @include header($english-ratio);
}

h6 {
  @include header($pica-ratio);
}

h1, h2 {
  margin-bottom: $line-height;
  margin-top: $line-height * 2;
}

p,
ul,
ol {
  margin-bottom: $leading-height;
}

ul ol,
ol ol,
ul ul,
ol ul {
  margin-bottom: 0;
}

ul {
  list-style-type: disc;
  margin-left: $indent-width;
}

ol {
  list-style-type: decimal;
  margin-left: $indent-width;
}

sub {
  line-height: 0;
  vertical-align: sub;
  font-size: $long-primer;
}

sup {
  line-height: 0;
  vertical-align: super;
  font-size: $long-primer;
}