a{
  padding: 0 10px;
  background-image: linear-gradient(to right, rgba(0, 0, 0, 0) 50%, rgb(49, 170, 226) 50%);
  background-position: 0 0;
  background-size: 200% auto;
  transition: .3s;
}

a:hover{
  background-position: -100% 0;
  color: #fff;
}
a:visited{
  color : #000;
}
a:hover{
  color : #000;
}
a:active{
  color : #000;
}
a{
  text-decoration: none;
}