Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="wrapper">
  
  <div class="a1"></div>
  
  <div class="a2"></div>
  <div class="a3"></div>
  
  <div class="two-third"></div>
  <div class="one-third"></div>
  
  <div class="centered">
    <div class="c1"></div>
    <div class="c2"></div>
  </div>
</div>

SassMeister-input.scss

// ----
// Sass (v3.3.5)
// Compass (v1.0.0.alpha.18)
// Susy (v)
// ----

@import "susy";

$susy: (
  columns: 12,
  gutter-position: split,
  debug: (
    image: show,
    color: rgba(255,255,0, 0.5),
    output: overlay,
    toggle: top right,
  ),
);

.wrapper {
  @include container;
  border: 1px dotted black;
  margin: 20px auto;
  width: 80%;
  
  div {
    height: 50px;
  }
  
}

.a1 {
  @include span(full);
  background-color: cyan;
}

.a2 {
  @include span(6);
  background-color: lightblue;
}

.a3 {
  @include span(last 4);
  background-color: lightblue;
}

.two-third {
  @include span(8 wide);
  background-color: cyan;
  margin-right: 0;
}

.one-third {
  @include span(4);
  background-color: Aquamarine;
  margin: 0;
}

.centered {
  @include span(6);
  @include push(3);
  background-color: pink;
}

.c1 {
  @include span(3 of 6);
  background-color: Fuchsia;
}

.c2 {
  @include span(3 of 6);
  background-color: Fuchsia;
}

SassMeister-output.css

.wrapper {
  max-width: 100%;
  margin-left: auto;
  margin-right: auto;
  border: 1px dotted black;
  margin: 20px auto;
  width: 80%;
}
.wrapper::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 ~ .wrapper, head:hover ~ body .wrapper {
  position: relative;
}
head:hover ~ .wrapper::before, head:hover ~ body .wrapper::before {
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  content: " ";
  z-index: 998;
  background-image: linear-gradient(to right, transparent 10%, rgba(255, 255, 0, 0.5) 10%, rgba(255, 255, 77, 0.5) 90%, transparent 90%);
  background-size: 8.33333%;
  background-origin: content-box;
  background-clip: content-box;
  background-position: left top;
}
.wrapper div {
  height: 50px;
}

.a1 {
  width: 98.33333%;
  float: left;
  margin-left: 0.83333%;
  margin-right: 0.83333%;
  background-color: cyan;
}

.a2 {
  width: 48.33333%;
  float: left;
  margin-left: 0.83333%;
  margin-right: 0.83333%;
  background-color: lightblue;
}

.a3 {
  width: 31.66667%;
  float: right;
  margin-left: 0.83333%;
  margin-right: 0.83333%;
  background-color: lightblue;
}

.two-third {
  width: 66.66667%;
  float: left;
  margin-left: 0.83333%;
  margin-right: 0.83333%;
  background-color: cyan;
  margin-right: 0;
}

.one-third {
  width: 31.66667%;
  float: left;
  margin-left: 0.83333%;
  margin-right: 0.83333%;
  background-color: Aquamarine;
  margin: 0;
}

.centered {
  width: 48.33333%;
  float: left;
  margin-left: 0.83333%;
  margin-right: 0.83333%;
  margin-left: 25.83333%;
  background-color: pink;
}

.c1 {
  width: 46.66667%;
  float: left;
  margin-left: 1.66667%;
  margin-right: 1.66667%;
  background-color: Fuchsia;
}

.c2 {
  width: 46.66667%;
  float: left;
  margin-left: 1.66667%;
  margin-right: 1.66667%;
  background-color: Fuchsia;
}

SassMeister-rendered.html

<div class="wrapper">
  
  <div class="a1"></div>
  
  <div class="a2"></div>
  <div class="a3"></div>
  
  <div class="two-third"></div>
  <div class="one-third"></div>
  
  <div class="centered">
    <div class="c1"></div>
    <div class="c2"></div>
  </div>
</div>