<a href="#" class="cp_btn">button</a>

a.cp_btn {
	position: relative;
	width: 160px;
	padding: 0.8em;
	text-align: center;
	font-weight: bold;
	text-decoration: none;
	color: #2196F3;
	transition: .4s;
}
a.cp_btn:before {
	position: absolute;
	display: inline-block;
	content: '';
	width: 4px;
	height: 100%;
	top: 0;
	left: 0;
	border-radius: 3px;
	background:#2196F3;
	transition: .2s;
}
a.cp_btn:after {
	position: absolute;
	display: inline-block;
	content: '';
	width: 4px;
	height: 100%;
	top:0;
	left: 100%;
	border-radius: 3px;
	background:#2196F3;
	transition: .2s;
}
a.cp_btn:hover:before,a.cp_btn:hover:after {
	transform: rotate(20deg);
}