<div class="container">
  <h1>Pure Css Button Hover effect</h1>
  
  <a href="#" class="button">Hover me</a>
  
<!--  optional  -->
  <span>Made by <a href="http://alticreation.com/en">alticreation.com</a></span>
</div>  

$color: #0cf;

.button {
  display: inline-block;
  padding: .75rem 1.25rem;
  border-radius: 10rem;
  color: #fff;
  text-transform: uppercase;
  font-size: 1rem;
  letter-spacing: .15rem;
  transition: all .3s;
  position: relative;
  overflow: hidden;
  z-index: 1;
  &:after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: $color;
    border-radius: 10rem;
    z-index: -2;
  }
  &:before {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0%;
    height: 100%;
    background-color: darken($color, 15%);
    transition: all .3s;
    border-radius: 10rem;
    z-index: -1;
  }
  &:hover {
    color: #fff;
    &:before {
      width: 100%;
    }
  }
}

/* optional reset for presentation */
* {
  font-family: Arial;
  text-decoration: none;
  font-size: 20px;
}
.container {
  padding-top: 50px;
  margin: 0 auto;
  width: 100%;
  text-align: center;
}
h1 {
  text-transform: uppercase;
  font-size: .8rem;
  margin-bottom: 2rem;
  color: #777;
}
span {
  display: block;
  margin-top: 2rem;
  font-size: .7rem;
  color: #777;
  a {
    font-size: .7rem;
    color: #999;
    text-decoration: underline;
  }
}