Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="container">
  <div class="col1">
    Left column
  </div>
  <div class="col2">
    Right column
  </div>
</div>

SassMeister-input.scss

// ----
// Sass (v3.4.7)
// Compass (v1.0.1)
// Susy (v2.1.3)
// ----

@import "susy";
@import 'compass/utilities/general/clearfix';

* {
  margin: 0;
  padding: 0;
}

$susy: (
  flow: ltr,
  math: fluid,
  output: inside,
  gutter-position: after,
  container: auto,
  container-position: center,
  columns: 2,
  gutters: 1/12,
  column-width: false,
  global-box-sizing: border-box,
  last-flow: to,
  debug: (
    image: show,
    color: rgba(#66f, .25),
    output: background,
    toggle: top right,
  ),
  use-custom: (
    background-image: true,
    background-options: false,
    box-sizing: true,
    clearfix: true,
    rem: true,
  )
);

.container {
  @include container(show overlay);
  @include clearfix;
  background: grey;
}

.col1 {
  @include span(1 of 2);
  background-color: red;
  @include gutters(8% 2 before);
}
.col2 {
  @include span(1 of 2 last);
  background-color: blue;
}

SassMeister-output.css

* {
  margin: 0;
  padding: 0;
}

.container {
  overflow: hidden;
  *zoom: 1;
  max-width: 100%;
  margin-left: auto;
  margin-right: auto;
  overflow: hidden;
  *zoom: 1;
  background: grey;
}
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 ~ .container, head:hover ~ body .container {
  position: relative;
}
head:hover ~ .container:before, head:hover ~ body .container: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) 92.30769%, transparent 92.30769%);
  background-size: 52.0%;
  background-origin: content-box;
  background-clip: content-box;
  background-position: left top;
}

.col1 {
  width: 48%;
  float: left;
  margin-right: 4.0%;
  background-color: red;
  margin-left: 8%;
}

.col2 {
  width: 48%;
  float: right;
  margin-right: 0;
  background-color: blue;
}

SassMeister-rendered.html

<div class="container">
  <div class="col1">
    Left column
  </div>
  <div class="col2">
    Right column
  </div>
</div>