limistah/index.html

## index.html
<html>

  <head>
    <link href="./program.css" rel="stylesheet" />
  </head>

  <body>
    <div class="app"> </div>
  </body>

</html>

## program.css
* {
  box-sizing: border-box;
}
html, body, .app {
 height: 100vh;
  width: 100vh;
  position: relative;
}
.app {
  background: linear-gradient()
}
.app::after {
  content: "Hello world!";
  position: absolute;
  width: 100%;
  height: 90vh;
  margin: auto 0;
  font-size: 2em;
  background: tomato;
  color: lightgrey;
  left: 0;
  right: 0;
}
	<html>

	<head>
	<link href="./program.css" rel="stylesheet" />
	</head>

	<body>
	<div class="app"> </div>
	</body>

	</html>
	* {
	box-sizing: border-box;
	}
	html, body, .app {
	height: 100vh;
	width: 100vh;
	position: relative;
	}
	.app {
	background: linear-gradient()
	}
	.app::after {
	content: "Hello world!";
	position: absolute;
	width: 100%;
	height: 90vh;
	margin: auto 0;
	font-size: 2em;
	background: tomato;
	color: lightgrey;
	left: 0;
	right: 0;
	}