compass/doc-src/content/stylesheets/partials/_theme.scss

@mixin site-theme($theme, $page-bg, $text, $strong-text, $heading, $link, $code, $search, $nav-link, $main-nav, $main-nav-selected, $docs-nav-selected, $module-nav-selected, $option-panel-text, $option-panel-border, $option-panel-bg){
  body {background: $page-bg; color: $text;
    a { color: $link; } }
  #page { @extend .horizontal-rule-#{$theme}; }
  header { @extend .horizontal-rule-#{$theme}; border-width: 4px; }
  #main-nav a[rel=home] { @include replace-text-with-dimensions("compass-logo-small-#{$theme}.png"); display: inline-block; }
  nav a { color: $nav-link; }
  
  #main-nav a { color: $main-nav;}
  body.home #main-nav a[rel=home],
  body.help #main-nav a[rel=help],
  body.docs #main-nav a[rel=documentation],
  body.get-involved #main-nav a[rel=get-involved]{ color: $main-nav-selected; }
  
  #sub-nav { @extend .horizontal-rule-#{$theme}; }
  #docs-nav { @extend .vertical-rule-#{$theme}; }
  body.core a[rel=core], body.blueprint a[rel=blueprint]{ @extend .inset-panel-#{$theme}; color: $docs-nav-selected; @extend .round-corners-4;}
  #module-nav {
    ul { overflow: visible; }
    li.selected { @extend .selected-marker-#{$theme};
      a { color: $module-nav-selected; } } }
  
  #search-docs {
    input::-webkit-input-placeholder { color: $search; }
    input { @extend .inset-panel-#{$theme}; color: $search;}}
  
  aside { @extend .vertical-rule-#{$theme};
    h2 { @extend .horizontal-rule-#{$theme};
      a { color: $strong-text; } } }
  
  #docs_panel > div {
    @include round-bottom-corners;
    background: $option-panel-bg; border: 1px solid $option-panel-border; border-top: 0;
    
    a[rel=theme] { @extend .theme-switch-#{$theme}; } }
  
  a[rel=sass], a[rel=scss] { @extend .syntax-switch-#{$theme} }
  
  #version { color: $option-panel-text; a { color: rgba($nav-link, .7); } }
  
  body.sass a[rel=sass], body.scss a[rel=scss] { color: rgba($heading, .7); @extend .round-corners-em; @extend .inset-panel-#{$theme}; }
  
  
  #page > article {
    #{headings()}{ color: $heading; }
    h1, h2 { @extend .horizontal-rule-#{$theme}; }
    h3 { @extend .heading-panel-#{$theme}; }
    h2 a.help { color: $heading;}
    .source-documentation { @extend .doc-panel-#{$theme}; }
  }
  
  footer .links li { @extend .vertical-rule-#{$theme}; }
  
  code { @extend .code-block-#{$theme}; color: $code; }
  .arg { color: $code; }
  .arg[data-default-value] { color: rgba($code, .7); }
  a[rel="view source"]{ color: rgba($heading, .5); &:hover{ color: rgba($heading, .8);} }
}

// Dark theme
.inset-panel-dark {
  @include box-shadow(rgba(#fff, .1) 0 1px 0, rgba(#000, .8) 0 1px 7px 0px inset);
  background-color: rgba(#000, .3); }
  
.horizontal-rule-dark {  
  @include box-shadow(rgba(#fff, .07) 0 1px 0);
  border-bottom: 1px solid #121212; }
  
.vertical-rule-dark {
  @include box-shadow(rgba(#fff, .07) 1px 0 0);
  border-right: 1px solid #121212; }
  
.code-block-dark { @extend .code-block; @extend .inset-panel-dark; }

.heading-panel-dark {
  background: rgba(#000, .2);
  @include box-shadow(rgba(#000, .2) 0 0 0 1px inset);
  a:hover { color: #fff;
    .arg { color: rgba(#fff, .6);}
  }
}
.doc-panel-dark {
  background: rgba(#000, .1);
  @include box-shadow(rgba(#000, .2) 0 0 0 1px inset);
}

.syntax-switch-dark {
  color: #000; text-shadow: rgba(#fff, .08) 0 1px 0;
  &:hover { color: #fff; text-shadow: #000 0 1px 0; } }

.theme-switch-dark {
  color: rgba(#000, .8); text-shadow: rgba(#fff, .08) 0 1px 0;
  &:hover { color: #eee; text-shadow: #000 0 1px 0; } }

.selected-marker-dark {
  a:before{ border-bottom-color: #121212; }
  &:before { border-bottom-color: #414141; }
  &:after { border-bottom-color: #323232; }
}

@mixin dark-theme {
  $page-bg: #343434;

  $text: #c6c6c6;
  $heading: white;
  $strong-text: #dbdbdb;

  $search: #6e6e6e;
  
  $link: #dadbb1;
  $nav-link: #bfbfbf;
  $code: #85AFC9;

  $main-nav: $strong-text;
  $main-nav-selected: #fb292d;
  $docs-nav-selected: $strong-text;
  $module-nav-selected: $link;

  $option-panel-text: rgba(#fff, .2);
  $option-panel-border: rgba(#000, .3);
  $option-panel-bg: rgba(#fff, .03);

  @include site-theme(dark, $page-bg, $text, $strong-text, $heading, $link, $code, $search, $nav-link, $main-nav, $main-nav-selected, $docs-nav-selected, $module-nav-selected, $option-panel-text, $option-panel-border, $option-panel-bg);
}

// Light Theme
.inset-panel-light {
  @include box-shadow(rgba(#fff, 1) 0 1px 0, rgba(#000, .5) 0 1px 3px 0px inset);
  text-shadow: 0 1px 1px #fff;
  background-color: rgba(#000, .04); }
  
.horizontal-rule-light {  
  @include single-box-shadow(rgba(#fff, 1), 0, 1px, 0);
  border-bottom: 1px solid #bbb; }
  
.vertical-rule-light {
  @include single-box-shadow(rgba(#fff, 1), 1px, 0, 0);
  border-right: 1px solid #bbb; }
  
.code-block-light { @extend .code-block; @extend .inset-panel-light;}

.syntax-switch-light {
  color: rgba(#000, .3); text-shadow: rgba(#fff, .08) 0 1px 0;
  &:hover { color: #000; text-shadow: #fff 0 1px 0; }}

.theme-switch-light {
  color: rgba(#000, .2); text-shadow: rgba(#fff, 1) 0 1px 0;
  &:hover { color: #000; } }

.heading-panel-light {
  background: #fff;
  @include box-shadow(rgba(#000, .2) 0 0 0 1px inset);
  a:hover { color: #000;
    .arg { color: rgba(#000, .6); } }
}

.selected-marker-light {
  a:before{ border-bottom-color: #bbbbbb; }
  &:before { border-bottom-color: #fff; }
  &:after { border-bottom-color: #e5e5e5; }
}

.doc-panel-light {
  background: rgba(#fff, .5);
  @include box-shadow(rgba(#000, .15) 0 0 0 1px inset);
}

@mixin light-theme {
  $page-bg: #ececec; // image-url('bg-light.jpg');

  $text: #222 ;
  $heading: black;
  $strong-text: #000;

  $search: #666;

  $link: #307eb6;
  $nav-link: #555;
  $code: #222;

  $main-nav: #555;
  $main-nav-selected: darken(#fb292d, 15);
  $docs-nav-selected: $strong-text;
  $module-nav-selected: $link;

  $option-panel-text: rgba(#000, .3);
  $option-panel-border: rgba(#000, .2);
  $option-panel-bg: #fff;

  @include site-theme(light, $page-bg, $text, $strong-text, $heading, $link, $code, $search, $nav-link, $main-nav, $main-nav-selected, $docs-nav-selected, $module-nav-selected, $option-panel-text, $option-panel-border, $option-panel-bg);
}

html.dark { @include dark-theme; }
html.light { @include light-theme; }