Layout Grid (BEM/SMACSS Style)

layout-2col-rendered.html

<div class="l-region-2cols--1-2">

  <div class="panel-pane">
    <h2 class="panel-title">Tardar Sauce</h2>
    <div class="panel-content">Grumpy Cat, real name Tardar Sauce, is a cat and Internet celebrity known for her grumpy facial expression. Her owner Tabatha Bundesen says that her permanently grumpy-looking face is due to feline dwarfism.</div>
  </div>
  
  <div class="panel-pane">
    <h2 class="panel-title">Tardar Sauce</h2>
    <div class="panel-content">Grumpy Cat, real name Tardar Sauce, is a cat and Internet celebrity known for her grumpy facial expression. Her owner Tabatha Bundesen says that her permanently grumpy-looking face is due to feline dwarfism.</div>
  </div>
  
</div>

layout-2col.css

* {
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
}

.l-region-2cols--1-2 {
  margin-bottom: 2em;
}
@media (min-width: 800px) {
  .l-region-2cols--1-2 > .panel-pane {
    width: 50%;
  }
  .l-region-2cols--1-2 > .panel-pane:nth-of-type(2n+1) {
    clear: left;
    float: left;
    padding-right: 1m;
  }
  .l-region-2cols--1-2 > .panel-pane:nth-of-type(2n+2) {
    clear: right;
    float: right;
    padding-left: 1m;
  }
}

.panel-pane {
  padding: 1em;
}

layout-2col.html

<div class="l-region-2cols--1-2">

  <div class="panel-pane">
    <h2 class="panel-title">Tardar Sauce</h2>
    <div class="panel-content">Grumpy Cat, real name Tardar Sauce, is a cat and Internet celebrity known for her grumpy facial expression. Her owner Tabatha Bundesen says that her permanently grumpy-looking face is due to feline dwarfism.</div>
  </div>
  
  <div class="panel-pane">
    <h2 class="panel-title">Tardar Sauce</h2>
    <div class="panel-content">Grumpy Cat, real name Tardar Sauce, is a cat and Internet celebrity known for her grumpy facial expression. Her owner Tabatha Bundesen says that her permanently grumpy-looking face is due to feline dwarfism.</div>
  </div>
  
</div>

layout-2col.scss

// ----
// Sass (v3.3.6)
// Compass (v)
// Breakpoint (v)
// ----

@import "compass";
@import "breakpoint";

$bp-med: 800px;

*{
  @include box-sizing(border-box);
}

// Default - 1 column to 2 cols @ bp-med
%l-region-2cols--1-2,
.l-region-2cols--1-2{
  //@extend %clearfix;
  margin-bottom: 2em;

  >.panel-pane{
    @include breakpoint($bp-med, $no-query: true){
      width: 50%;

      &:nth-of-type(2n+1){
        clear: left;
        float: left;
        padding-right: 1m;
      }

      &:nth-of-type(2n+2){
        clear: right;
        float: right;
        padding-left: 1m;
      }
    }
  }
}

.panel-pane{
  padding: 1em;
}