JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container clearfix">
  <div class="block">1</div>
  <div class="block">2</div>
  <div class="block">3</div>
  <div class="block">4</div>
  <div class="block">5</div>
  <div class="block">6</div>
  <div class="block">7</div>
  <div class="block">8</div>
  <div class="block">9</div>
  <div class="block">10</div>
  <div class="block">11</div>
  <div class="block">12</div>
  <div class="block">13</div>
  <div class="block">14</div>
</div>

CSS

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

.clearfix:after {
  content: '';
  dispaly: table;
  clear: both;
}

.block {
  float: left;
  width: 50%;
  padding: 15px;
  background: #eee;
  border: 1px solid #333;
  text-align: center;
}
.block:nth-child(4n+3) {
  float: right;
}