.wrap {
	display: flex;
	justify-content: center;
	align-items: center;
	height: 100vh;
	flex-direction: column;
}

.btn {
	border: 1px solid #ddd;
	padding: 5px;
	display: inline-block;
	position: relative;
	text-decoration: none;
	font-size: 1em;
	color: black;
}

.btn-slack:before {
	content: '';
	display: inline-block;
	background-image: url('images/slack.png');
	background-repeat: no-repeat;
	background-size: cover;
	vertical-align: middle;
	width: 30px;
	height: 30px;
}

pre {
	background-color: #ddd;
	display: inline-block;
	border: 1px solid #000;
}