<div class="element no1">
  <div class="element no2">
    <div class="element no3">3</div>
  </div>
</div>



.element {
  display: block;
  width: 75%;
  height: 75%;
  padding: 0;
}

.no1 {
  width: 100vmin;
  height: 100vmin;
}

.no3 { display: flex; }

External CSS

  1. https://tim-montmorency.com/timdoc/shared/styles/codepen.css
  2. https://tim-montmorency.com/timdoc/shared/styles/codepen-position.css

External JavaScript

This Pen doesn't use any external JavaScript resources.