JSFiddle - React, Tailwind, and code Playground

HTML

<div class="screen">
  <div class="centering-column">
    <div class="centering-row">
        <div class="myContent">
          middle f'diddle!
        </div>
    </div>
  </div>
</div>

CSS

.screen {
  height: 400px;
  width: 400px;
  border: 5px solid black;
}

.centering-column {
  display: flex;
  height: 100%;
  flex-direction: column;
  justify-content: center;
  background-color: green;
}

.centering-row {
  display: flex;
  justify-content: center;
  background-color: blue;
}

.myContent {
  color: white;
}