JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
<head>
<style>
  *
  {
	box-sizing: border-box;
	
}

html, body
{
  height:100%;
  width:100%;
  margin:0;
  padding:0;
  background-color: #2f323f;
}
#pojemnik
{
	width: 70%;
  height:70%;
  background-color: red;
  margin:0 auto;
}

#modul1
{
	width:100%;
  height: 50%;
	background-color: white;
}
  
  
 </style>
</head>
<body>

  <div id="pojemnik">
    <div id="modul1"></div>
  </div>

</body>
</html>