* {
	box-sizing: border-box;
}

body {
	margin: 0;
	padding: 0;
	font-family: helvetica, arial, sans-serif;
}

.wrapper {
	margin: 0 auto;
	background-color: #f1f1f1;
	width: 100%;
	font-size: 0px;
}

.c {
	padding: 0 15px 0px 15px;
	margin: 0 0 50px 0;
	background-color: #ffa;
	display: inline-block;
	font-size: 15px;
}

.c1 { width: 25%; }

.c2 { width: 50%; }

.c3 { width: 75%; }

.c4 { width: 100%; }

.button-wrapper {
	position: fixed;
	top: 50%;
	left: 50%;
	transform: translate(-50%, -50%);
}

.button {
	display: block;
	width: 175px;
	height: 175px;
	background: black;
	color: #fff;
	border-radius: 50%;
	font-size: 15px;
	text-decoration: none;
	transition: all 500ms ease;

}

.button-text {
	position: absolute;
	top: 50%;
	left: 50%;
	transform: translate(-50%, -50%);
}

.button:hover {
	background: #ff0;
	transform: rotate(90deg);
}