Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="parent">
  <div class="child">
    <p>child 1</p>
    <div class="grandchild">Grandchild 1</div>
    <div class="grandchild last">Grandchild 2</div>
  </div>  
  <div class="child last">child 2</div>  
</div>

SassMeister-input.scss

// ----
// Sass (v3.3.12)
// Compass (v1.0.0.alpha.21)
// Susy (v2.1.3)
// ----

@import "compass";
@import "susy";

*, *:before, *:after {
  -moz-box-sizing: border-box; -webkit-box-sizing: border-box; box-sizing: border-box;
}

$susy: (
  columns: 12,
  column-width: 4em,
  gutters: 1/4,
  math: fluid,
  output: float,
  gutter-position:inside,
  global-box-sizing: border-box,
  debug: (
    image: show,
    color: rgba(200,100,100,.3),
    output: overlay,
    toggle: top right,
  ),
);

.parent {
  @include container();
  @include show-grid(background);
  padding:0;
  @include clearfix;
  }
  
.child {
  background-color: rgba(100,100,200, 0.5);
  @include span(first 6 of 12);
  &.last {
    @include span(last 6 of 12);
  }
}

.grandchild {
  background-color: rgba(100,100,200, 0.5);
  @include span(first 3 of 6);
  &.last {
    @include span(last 3 of 6);
  }
}

SassMeister-output.css

.parent {
  max-width: 60em;
  margin-left: auto;
  margin-right: auto;
  background-image: url('data:image/svg+xml;base64,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'), url('data:image/svg+xml;base64,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');
  background-size: 100%;
  background-image: -moz-linear-gradient(left, rgba(200, 100, 100, 0.3), rgba(220, 156, 156, 0.3)), -moz-linear-gradient(top, rgba(0, 0, 0, 0.5) 1px, rgba(0, 0, 0, 0) 1px);
  background-image: -webkit-linear-gradient(left, rgba(200, 100, 100, 0.3), rgba(220, 156, 156, 0.3)), -webkit-linear-gradient(top, rgba(0, 0, 0, 0.5) 1px, rgba(0, 0, 0, 0) 1px);
  background-image: linear-gradient(to right, rgba(200, 100, 100, 0.3), rgba(220, 156, 156, 0.3)), linear-gradient(to bottom, rgba(0, 0, 0, 0.5) 1px, rgba(0, 0, 0, 0) 1px);
  background-size: 8.33333%, 100% 24px;
  background-origin: content-box, border-box;
  background-clip: content-box, border-box;
  background-position: left top;
  padding: 0;
  overflow: hidden;
  *zoom: 1;
}
.parent: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 ~ .parent, head:hover ~ body .parent {
  position: relative;
}
head:hover ~ .parent:before, head:hover ~ body .parent:before {
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  content: " ";
  z-index: 998;
  background-image: url('data:image/svg+xml;base64,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'), url('data:image/svg+xml;base64,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');
  background-size: 100%;
  background-image: -moz-linear-gradient(left, rgba(200, 100, 100, 0.3), rgba(220, 156, 156, 0.3)), -moz-linear-gradient(top, rgba(0, 0, 0, 0.5) 1px, rgba(0, 0, 0, 0) 1px);
  background-image: -webkit-linear-gradient(left, rgba(200, 100, 100, 0.3), rgba(220, 156, 156, 0.3)), -webkit-linear-gradient(top, rgba(0, 0, 0, 0.5) 1px, rgba(0, 0, 0, 0) 1px);
  background-image: linear-gradient(to right, rgba(200, 100, 100, 0.3), rgba(220, 156, 156, 0.3)), linear-gradient(to bottom, rgba(0, 0, 0, 0.5) 1px, rgba(0, 0, 0, 0) 1px);
  background-size: 8.33333%, 100% 24px;
  background-origin: content-box, border-box;
  background-clip: content-box, border-box;
  background-position: left top;
}

.child {
  background-color: rgba(100, 100, 200, 0.5);
  width: 50%;
  float: left;
  padding-left: 0.83333%;
  padding-right: 0.83333%;
}
.child.last {
  width: 50%;
  float: right;
  padding-left: 0.83333%;
  padding-right: 0.83333%;
}

.grandchild {
  background-color: rgba(100, 100, 200, 0.5);
  width: 50%;
  float: left;
  padding-left: 1.66667%;
  padding-right: 1.66667%;
}
.grandchild.last {
  width: 50%;
  float: right;
  padding-left: 1.66667%;
  padding-right: 1.66667%;
}

SassMeister-rendered.html

<div class="parent">
  <div class="child">
    <p>child 1</p>
    <div class="grandchild">Grandchild 1</div>
    <div class="grandchild last">Grandchild 2</div>
  </div>  
  <div class="child last">child 2</div>  
</div>