<style>
.links {
display:block;
}
.links a {
display:inline;
width: 150px;
box-shadow: inset 0 0 0 0 #000;
overflow: visible;
-webkit-transition: all ease 0.5s;
-moz-transition: all ease 0.5s;
transition: all ease 0.5s;}
.links a:hover {
box-shadow: inset 0 50px 0 0 #000;}
</style>