tweet css grid

HTML

<div>
  <div class="_">6</div>
  <div>
    <div class="_1">1</div>
    <div class="_2">2</div>
    <div class="_3">3</div>
  </div>
  <div>
    <div class="_2">2</div>
    <div class="_2">2</div>
    <div class="_2">2</div>
  </div>
  <div>
    <div class="_3">3</div>
    <div class="_3">3</div>
  </div>
  <div>
    <div class="_4">4</div>
    <div class="_2">2</div>
  </div>
  <div>
    <div class="_5">5</div>
    <div class="_1">1</div>
  </div>
</div>

CSS

* {
  margin: 0;
  padding: 0;
}

/* grid */
[class*=_]{float:left;box-sizing:border-box}._{width:100%}._1{width:16.67%}._2{width:33.33%}._3{width:50%}._4{width:66.67%}._5{width:83.33%}

/* visual styles */
body{background: orange;}
[class*=_]{border: solid 1px white;}