sliding underline on links

/*SLIDE IN FROM LEFT*/
a {
color:#6d7fff;
text-decoration:none;
position:relative;
-webkit-transition: all 0.4s ease-in-out;
-moz-transition: all 0.4s ease-in-out;
-o-transition: all 0.4s ease-in-out;
transition: all 0.4s ease-in-out;
}
a:hover {
color:#000;
}
a:after {
content:'';
position:absolute;
bottom:0;
left:0;
width:0%;
border-bottom:1px solid #000;
transition:0.4s;
}
a:hover:after {
width:100%;
}

/*SLIDE IN FROM RIGHT*/
a {
color:#6d7fff;
display: inline-block;
position: relative;
text-decoration:none;
-webkit-transition: all 0.4s ease-in-out;
-moz-transition: all 0.4s ease-in-out;
-o-transition: all 0.4s ease-in-out;
transition: all 0.4s ease-in-out;
}
a:hover {
color:#000;
}
a:after {
content: '';
display: block;
position: absolute;
right: 0;
bottom: 0;
height: 1px;
width: 0;
background: transparent;
transition: width .5s ease, background-color .5s ease;
}
a:hover:after {
width: 100%;
background:#000;
}

/*SLIDE IN AND OFF*/
a {
color:#6d7fff;
text-decoration:none;
position:relative;
-webkit-transition: all 0.4s ease-in-out;
-moz-transition: all 0.4s ease-in-out;
-o-transition: all 0.4s ease-in-out;
transition: all 0.4s ease-in-out;
}
a:hover {
color:#000;
}
a:before {
content: '';
display: block;
position: absolute;
left: 0;
bottom: 0;
height: 3px;
width: 0;
transition: width 0s ease, border-bottom .5s ease;
}
a:after {
content: '';
display: block;
position: absolute;
right: 0;
bottom: 0;
height: 3px;
width: 0;
border-bottom: 1px solid #000;
transition: width .5s ease;
}
a:hover:before {
width: 100%;
border-bottom: 1px solid #000;
transition: width .5s ease;
}
a:hover:after {
width: 100%;
border-bottom: transparent;
transition: all 0s ease;
}

/*SLIDE MIDDLE OUT*/
a {
color:#6d7fff;
display: inline-block;
position: relative;
text-decoration:none;
}
a:hover {
color:#000;
}
a:after {
content: '';
display: block;
margin: auto;
height: 1px;
width: 0px;
background: transparent;
transition: width .5s ease, background-color .5s ease;
}
a:hover:after {
width: 100%;
background: #000;
}