Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="container">
<section class="first-section">
    <img src="http://placekitten.com/g/200/200" >
    <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit</p>
</section>

<section class="second-section">
    <img src="http://placekitten.com/g/200/200" >
    <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit</p>
</section>

<section class="third-section">
    <img src="http://placekitten.com/g/200/200" >
    <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit</p>
</section>

<section class="fourth-section">
    <img src="http://placekitten.com/g/200/200" >
    <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit</p>
</section>
</div>

SassMeister-input.scss

// ----
// Sass (v3.3.14)
// Compass (v1.0.1)
// Breakpoint (v2.5.0)
// Toolkit (v2.6.0)
// ----

@import "breakpoint";
@import "singularitygs";
@import "toolkit";
@import "toolkit/kickstart";

@include add-grid(2);
@include add-grid(3 5 at 600px);
@include add-grid(2 8 2 at 1000px);
@include add-gutter(1/3);
@include sgs-change('output', 'isolation');



.container {
  max-width: 65em;
}

@include breakpoint(630px 1079px) {
  .first-section, .fourth-section {
    @include grid-span(1, 2);
  }
  
  .second-section, .third-section {
    @include isolation-span(1, 1, $clear: 'left');
  }
}

@include breakpoint(1080px) {
  .first-section {
    @include grid-span(1, 2);
  }
  
  .second-section, .fourth-section {
    @include isolation-span(1, 1);
  }
  
  .fourth-section {
    clear: left;
  }
  
  .third-section {
    @include grid-span(1, 3);
  }
}

SassMeister-output.css

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

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

.container {
  max-width: 65em;
}

@media (min-width: 630px) and (max-width: 1079px) {
  .first-section, .fourth-section {
    width: 60%;
    float: right;
    margin-left: 0;
    margin-right: 0;
    clear: none;
  }

  .second-section, .third-section {
    width: 36%;
    float: left;
    margin-right: -100%;
    margin-left: 0;
    clear: left;
  }
}
@media (min-width: 1080px) {
  .first-section {
    width: 63.15789%;
    float: left;
    margin-right: -100%;
    margin-left: 18.42105%;
    clear: none;
  }

  .second-section, .fourth-section {
    width: 15.78947%;
    float: left;
    margin-right: -100%;
    margin-left: 0;
    clear: none;
  }

  .fourth-section {
    clear: left;
  }

  .third-section {
    width: 15.78947%;
    float: right;
    margin-left: 0;
    margin-right: 0;
    clear: none;
  }
}

SassMeister-rendered.html

<div class="container">
<section class="first-section">
    <img src="http://placekitten.com/g/200/200" >
    <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit</p>
</section>

<section class="second-section">
    <img src="http://placekitten.com/g/200/200" >
    <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit</p>
</section>

<section class="third-section">
    <img src="http://placekitten.com/g/200/200" >
    <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit</p>
</section>

<section class="fourth-section">
    <img src="http://placekitten.com/g/200/200" >
    <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit</p>
</section>
</div>