popup.css

/* import font */
@import url('https://fonts.googleapis.com/css?family=Roboto:300,400,500,700');

* {
	box-sizing: border-box;
	font-family: 'Roboto', sans-serif;
}

body {
	width: 300px;
	height: 200px;
	background-color: #f0f0f0;
	padding: 0;
	margin: 0;
	display: flex;
	justify-content: center;
	align-items: center;
}

.center {
	position: relative;
	text-align: center;
}

#btn {
	background-color: #4CAF50;
	/* Green */
	border: none;
	color: white;
	padding: 15px 32px;
	text-align: center;
	text-decoration: none;
	display: inline-block;
	font-size: 16px;
	margin: 4px 2px;
	cursor: pointer;
	border-radius: 4px;
}

#btn:hover {
	background-color: #45a049;
}

.social-media {
	margin-top: 20px;
}

.social-media a {
	color: #333;
	text-decoration: none;
	margin-right: 10px;
	font-size: 17px;
}

.social-media a i {
	font-size: 20px;
}

.social-media a i.fa-github:hover {
	color: #4078c0;
}