JSFiddle - React, Tailwind, and code Playground

HTML

<body class="app">
<section>
  <h2>
  Hello
  </h2>
</section>
</body>

CSS

html{
height:100%; 
}

body.app {
  height:100%;
  margin:0;
  padding:0;
  background-color:#00aa00;
}

section {
  margin:0;
  padding:0;
  background-color:#aa0000;
}

h2 {
  margin-top:0px;
  margin-top:50px;
}