body {
  text-align: center;
  margin: 100px;
}
a {
  font-size: 40px;
  display: inline-block;
  position: relative;
  overflow: hidden;
  text-decoration: none;
  
  &:after {
    content: '';
    width: 20%;
    height: 100%;
    position: absolute;
    left: auto;
    top: 0;
    bottom: 0;
    right: -20%;
    background-image: 
      linear-gradient(135deg, 
        rgba(255,255,255,0),
        rgba(255,255,255,.8),
        rgba(255,255,255,0)
      );
  }
  &:hover {
    
    &:after {
    transition: all .4s ease-out;
      right: 100%;
    }
  }
}