<div class="wrapper">
  <a href="#">Hover Me!</a>
</div>

.wrapper{
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

a{
  display: block;
  font-size: 24px;
  font-family: sans-serif;
  text-decoration: none;
  color: #333;
  border-top: 2px solid #333;
  border-bottom: 2px solid #333;
  padding: 10px;
  letter-spacing: 2px;
  transition: all .25s;
}

a:hover{
  letter-spacing: 15px;
}