demo.css

html {
	background:#222;
	margin:auto;
	width:80%;
}

body{
	background: linear-gradient(#aaa 0, #ddd 10px, #fff 55px);
	border: 1px solid black;
	padding: 10px 20px;
	box-shadow: 5px 0px 30px #000;
	border-radius: 8px;
}

h1 {
	text-align: center;
	color: #222;
	margin: 0 0 30px;
}

.button {
	color: #333;
	background: linear-gradient(#eee, #ddd);
	border: 1px solid #222;
	border-radius: 3px;
	padding: 7px;
	margin-right: 5px;
	transition: .3s;
	font-family: ubuntu, sans-serif;
	font-size: 1em;
}

.button:active {
	background: linear-gradient(#ddd, #eee);
}

.button:hover, button:focus {
	box-shadow: 0 0 2px #222;
}

#execute {
	margin-top: 5px;;
	width: 10%;
	min-width:100px;
}

.CodeMirror {
  border: 1px solid #222;
  height: auto;
}
.CodeMirror-scroll {
  overflow-y: hidden;
  overflow-x: auto;
}

.error {
	color:red;
	transition:.5s;
	overflow:hidden;
	margin: 15px;
}

#output {
	overflow: auto;
}

table {
	width:auto;
	margin:auto;
	border:1px solid black;
 	border-collapse:collapse;
 	margin-bottom:10px;
}

th, td {
	border:1px solid #777;
}

footer {
	font-size:.8em;
	color: #222;
}