Generated by SassMeister.com.

SassMeister-input-HTML.haml

%header.site-header
  .wrap
    .logo
      %a{ href: "#" }
        Logo
    %nav
      %ul
        - 5.times do | i |
          %a{ href: "#" }
            item0#{i}
.wrap
  %main.content
    %h2 Gallery Content
    %ul.gallery
      - 15.times do | i | 
        %li.gallery__item
          %img{ src: "http://www.placehold.it/250x250&text=item#{i}" }
  %aside.sidebar
    %h2 
      Sidebar
    %ul
      - 5.times do 
        %li
          %a{ href: "#" } A link to someplace else

.site-footer
  .wrap
    - 4.times do |i|
      .widget
        %h2 
          Widget
  

SassMeister-input.scss

// ----
// Sass (v3.4.14)
// Compass (v1.0.3)
// Breakpoint (v2.5.0)
// Susy (v2.2.5)
// Toolkit (v2.9.0)
// ----

// Second edition after review feedback from me & others; practice makes perfect
@import "susy";
@import "toolkit";
@import "toolkit/kickstart";
@import "breakpoint";

//Variables
$breakpoint-to-ems: true;
$susy: ( columns: 8, debug: (image: show, color: rgba(#66f, .25), output: overlay), global-box-sizing: border-box, container: 1140px);
$tablet: 600px;
$desktop: 980px;

// Mixins
@mixin cf {
  &:after {
    content: " ";
    display: block;
    clear: both;
  }
}


:root {
  font-family: sans-serif;
}
ul, ol, li {
  margin: 0;
  padding: 0;
}

li {
  list-style: none;
}

.wrap {
  @include container();
  padding: {
  };
  
  @include breakpoint($tablet) {
    @include show-grid(9);
  }
  
  @include breakpoint($desktop){
    @include show-grid(16)
  }
}

.site-header, .site-footer {
  background: rgba(234, 159, 195, 0.8);
}

.site-header {
  a { 
    color: #555;
    text-decoration: none;
  }
}

.logo {
  float: left;
  line-height: 2rem;
  font-size: 1.5rem;
}

nav {
  float: right;
  
  li {
    list-style: none;
    float: left;
    margin-left: 1em;
    line-height: 2rem;
  }
}

.content {
  margin-top: 10vh;
  background: rgba(113, 218, 210, 0.8);
  @include susy-breakpoint($desktop, 16){
    @include span(12 of 16);
  }
}

.sidebar {
  margin-top: 10vh;
  background: rgba(250, 231, 179, 0.8);
  @include susy-breakpoint($desktop, 16) {
    @include span(4 of 16 last);
  }
  a {
    color: #666;
    padding-left: 1rem;
    line-height: 2;
    text-decoration: none;
  }
}

.widget {
  background: rgba(240, 150, 113, 0.8);
}

h2 { 
  padding: 1rem 0;
  text-align: center;
  color: #555;
}

.gallery {
  background: rgb(200, 200, 2);
  @include cf;
  @include susy-breakpoint($desktop, 12){
    width: span(10 of 12);
    margin-left: span(1 wide of 12);
  }
  // === margin-left: span(1 of 12) + gutter(12)
  @include susy-breakpoint(max-width $tablet, 8) {
    
    @include nested(8){
      &__item {
        margin-bottom: gutter();
        @include gallery(4)
      }
    }
  }
  
  @include susy-breakpoint(max-width $desktop, 9){
    &__item {
      margin-bottom: gutter();
      @include gallery(3 of 9);
    }
  }
  
  @include susy-breakpoint($desktop, 16) {
    @include nested(10){
      &__item {
        margin-bottom: gutter();
        @include gallery(2);
      }
    }
  }
  
  &__item {
    /*
    @include span( 2 of 10);
    margin-bottom: gutter(10);
    &:nth-child(5n) {
      @include last
    }
    */
  }
}

.widget {
  @include gallery( 4 of 16 )
}

SassMeister-output.css

html {
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

*, *:before, *:after {
  box-sizing: inherit;
}

embed,
img,
object,
video {
  max-width: 100%;
  height: auto;
}

:root {
  font-family: sans-serif;
}

ul, ol, li {
  margin: 0;
  padding: 0;
}

li {
  list-style: none;
}

.wrap {
  max-width: 1140px;
  margin-left: auto;
  margin-right: auto;
}
.wrap:after {
  content: " ";
  display: block;
  clear: both;
}
head {
  display: block;
  position: fixed;
  right: 10px;
  top: 10px;
  z-index: 999;
  color: #333;
  background: rgba(255, 255, 255, 0.25);
}
head:before {
  content: "|||";
  display: block;
  padding: 5px 10px;
  font-family: sans-serif;
  font-size: 16px;
  font-weight: bold;
}
head:hover {
  background: rgba(255, 255, 255, 0.5);
  color: red;
}
head:hover ~ .wrap, head:hover ~ body .wrap {
  position: relative;
}
head:hover ~ .wrap:before, head:hover ~ body .wrap:before {
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  content: " ";
  z-index: 998;
  background-image: linear-gradient(to right, rgba(102, 102, 255, 0.25), rgba(179, 179, 255, 0.25) 80%, transparent 80%);
  background-size: 12.82051%;
  background-origin: content-box;
  background-clip: content-box;
  background-position: left top;
}
@media (min-width: 37.5em) {
  head:hover ~ .wrap, head:hover ~ body .wrap {
    position: relative;
  }
  head:hover ~ .wrap:before, head:hover ~ body .wrap:before {
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
    content: " ";
    z-index: 998;
    background-image: linear-gradient(to right, rgba(102, 102, 255, 0.25), rgba(179, 179, 255, 0.25) 80%, transparent 80%);
    background-size: 11.36364%;
    background-origin: content-box;
    background-clip: content-box;
    background-position: left top;
  }
}
@media (min-width: 61.25em) {
  head:hover ~ .wrap, head:hover ~ body .wrap {
    position: relative;
  }
  head:hover ~ .wrap:before, head:hover ~ body .wrap:before {
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
    content: " ";
    z-index: 998;
    background-image: linear-gradient(to right, rgba(102, 102, 255, 0.25), rgba(179, 179, 255, 0.25) 80%, transparent 80%);
    background-size: 6.32911%;
    background-origin: content-box;
    background-clip: content-box;
    background-position: left top;
  }
}

.site-header, .site-footer {
  background: rgba(234, 159, 195, 0.8);
}

.site-header a {
  color: #555;
  text-decoration: none;
}

.logo {
  float: left;
  line-height: 2rem;
  font-size: 1.5rem;
}

nav {
  float: right;
}
nav li {
  list-style: none;
  float: left;
  margin-left: 1em;
  line-height: 2rem;
}

.content {
  margin-top: 10vh;
  background: rgba(113, 218, 210, 0.8);
}
@media (min-width: 61.25em) {
  .content {
    width: 74.68354%;
    float: left;
    margin-right: 1.26582%;
  }
}

.sidebar {
  margin-top: 10vh;
  background: rgba(250, 231, 179, 0.8);
}
@media (min-width: 61.25em) {
  .sidebar {
    width: 24.05063%;
    float: right;
    margin-right: 0;
  }
}
.sidebar a {
  color: #666;
  padding-left: 1rem;
  line-height: 2;
  text-decoration: none;
}

.widget {
  background: rgba(240, 150, 113, 0.8);
}

h2 {
  padding: 1rem 0;
  text-align: center;
  color: #555;
}

.gallery {
  background: #c8c802;
}
.gallery:after {
  content: " ";
  display: block;
  clear: both;
}
@media (min-width: 61.25em) {
  .gallery {
    width: 83.05085%;
    margin-left: 8.47458%;
  }
}
@media (max-width: 37.5em) {
  .gallery__item {
    margin-bottom: 2.5641%;
    width: 48.71795%;
    float: left;
  }
  .gallery__item:nth-child(2n + 1) {
    margin-left: 0;
    margin-right: -100%;
    clear: both;
    margin-left: 0;
  }
  .gallery__item:nth-child(2n + 2) {
    margin-left: 51.28205%;
    margin-right: -100%;
    clear: none;
  }
}
@media (max-width: 61.25em) {
  .gallery__item {
    margin-bottom: 2.27273%;
    width: 31.81818%;
    float: left;
  }
  .gallery__item:nth-child(3n + 1) {
    margin-left: 0;
    margin-right: -100%;
    clear: both;
    margin-left: 0;
  }
  .gallery__item:nth-child(3n + 2) {
    margin-left: 34.09091%;
    margin-right: -100%;
    clear: none;
  }
  .gallery__item:nth-child(3n + 3) {
    margin-left: 68.18182%;
    margin-right: -100%;
    clear: none;
  }
}
@media (min-width: 61.25em) {
  .gallery__item {
    margin-bottom: 2.04082%;
    width: 18.36735%;
    float: left;
  }
  .gallery__item:nth-child(5n + 1) {
    margin-left: 0;
    margin-right: -100%;
    clear: both;
    margin-left: 0;
  }
  .gallery__item:nth-child(5n + 2) {
    margin-left: 20.40816%;
    margin-right: -100%;
    clear: none;
  }
  .gallery__item:nth-child(5n + 3) {
    margin-left: 40.81633%;
    margin-right: -100%;
    clear: none;
  }
  .gallery__item:nth-child(5n + 4) {
    margin-left: 61.22449%;
    margin-right: -100%;
    clear: none;
  }
  .gallery__item:nth-child(5n + 5) {
    margin-left: 81.63265%;
    margin-right: -100%;
    clear: none;
  }
}
.gallery__item {
  /*
  @include span( 2 of 10);
  margin-bottom: gutter(10);
  &:nth-child(5n) {
    @include last
  }
  */
}

.widget {
  width: 24.05063%;
  float: left;
}
.widget:nth-child(4n + 1) {
  margin-left: 0;
  margin-right: -100%;
  clear: both;
  margin-left: 0;
}
.widget:nth-child(4n + 2) {
  margin-left: 25.31646%;
  margin-right: -100%;
  clear: none;
}
.widget:nth-child(4n + 3) {
  margin-left: 50.63291%;
  margin-right: -100%;
  clear: none;
}
.widget:nth-child(4n + 4) {
  margin-left: 75.94937%;
  margin-right: -100%;
  clear: none;
}

SassMeister-rendered.html

<header class='site-header'>
  <div class='wrap'>
    <div class='logo'>
      <a href='#'>
        Logo
      </a>
    </div>
    <nav>
      <ul>
        <a href='#'>
          item00
        </a>
        <a href='#'>
          item01
        </a>
        <a href='#'>
          item02
        </a>
        <a href='#'>
          item03
        </a>
        <a href='#'>
          item04
        </a>
      </ul>
    </nav>
  </div>
</header>
<div class='wrap'>
  <main class='content'>
    <h2>Gallery Content</h2>
    <ul class='gallery'>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item0'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item1'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item2'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item3'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item4'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item5'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item6'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item7'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item8'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item9'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item10'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item11'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item12'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item13'>
      </li>
      <li class='gallery__item'>
        <img src='http://www.placehold.it/250x250&amp;text=item14'>
      </li>
    </ul>
  </main>
  <aside class='sidebar'>
    <h2>
      Sidebar
    </h2>
    <ul>
      <li>
        <a href='#'>A link to someplace else</a>
      </li>
      <li>
        <a href='#'>A link to someplace else</a>
      </li>
      <li>
        <a href='#'>A link to someplace else</a>
      </li>
      <li>
        <a href='#'>A link to someplace else</a>
      </li>
      <li>
        <a href='#'>A link to someplace else</a>
      </li>
    </ul>
  </aside>
</div>
<div class='site-footer'>
  <div class='wrap'>
    <div class='widget'>
      <h2>
        Widget
      </h2>
    </div>
    <div class='widget'>
      <h2>
        Widget
      </h2>
    </div>
    <div class='widget'>
      <h2>
        Widget
      </h2>
    </div>
    <div class='widget'>
      <h2>
        Widget
      </h2>
    </div>
  </div>
</div>