JSFiddle - React, Tailwind, and code Playground

by Valentin Sarychev

HTML

<div class="container">
  <div class="block">
  
  </div>
</div>

CSS

.container {
  display: flex;
  justify-content: center;
  align-items: center;
  background: blue;
  border: 5px solid green;
  width: 480px;
  min-height: 250px;
  height: 0; /* это важно */
  box-sizing: border-box;
}

.block {
  background: red;
  border: 5px solid yellow;
  width: 100%;
  height: 100%;
  box-sizing: border-box;
}