JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div class="column">
    50%
  </div>
  <div class="column">
    50%
  </div>
  <div class="column">
    50%
  </div>
  <div class="column">
    50%
  </div>
</div>

CSS

html, body {
  height: 100%;
  margin: 0;
}
.container {
  height: 100%;
}
.column {
  height: 25%;  
  display: flex;                         /*  added  */
  justify-content: center;               /*  hor. center  */
  align-items: center;                   /*  ver. center  */
}

@media screen and (min-width: 600px) {
  .container {
    display: flex;
    flex-wrap: wrap;
  }
  .column {
    flex-basis: 50%;
    height: 50%;
  }
}


/* general styles */
body {
  font-family: 'Lato', sans-serif;
  font-size: 1.3em;
  color: #ccc;
  background: #000;
  /*margin-bottom: 70px;*/
}

.column {
  padding: 15px;
  /*border: 1px solid #666;*/
  box-sizing: border-box;
}

.column:nth-child(1) {
  background: #5c9;
}
.column:nth-child(2) {
  background: #fb0;
}
.column:nth-child(3) {
  background: #39f;
}
.column:nth-child(4) {
  background: #f33;
}

main {
  max-width: 1200px;
  margin: 0 auto;
}

h1,
h2 {
  text-align: center;
}