<a href="#" class="cp_btn"><span>button</span></a>
a.cp_btn {
display: block;
text-decoration:none;
width: 160px;
padding: 0.8em;
text-align: center;
color: #FFF;
border-radius: 4px;
background: #4DD0E1;
overflow: hidden;
}
a.cp_btn span {
display:inline-block;
transition: .5s
}
a.cp_btn:hover span {
transform: rotateX(360deg);
}