Light highlight effect

#code/css

https://codepen.io/makzan/details/GoBLBP

a.box {
  padding: 3em;
  display: inline-block;
  color: white;
  font-weight: bolder;
  text-decoration: none;
  text-shadow: 0 1px 1px rgba(0,0,0,.9);
  background: gray;
  background-position: center center;
  background-size: cover;
  position: relative;
  overflow: hidden;
  letter-spacing: -0.02em;
  text-rendering: optimizeLegibility;
  margin: .3em;
  
  border-radius: 3px;
  
  transition: all 0.3s ease-out;
  
  /* shadow */
  &:before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    // border: 1px solid red;

  }
  
  /* highlight */
  &:after {
    content: '';
    position: absolute;
    top: -60%;
    left: 0%;
    width: 60%;
    height: 100%;
    background-image: linear-gradient(to bottom, rgba(255,255,255,0.6) 0%, rgba(255,255,255,0) 100%);
    transform: translate3d(-50%, 0, 0) rotateZ(45deg);
    
    opacity: 0;
    transition: all 0.3s ease-out;
  }
  
  &:hover {
    // transform: scale3d(1.09,1.09,1);
    transition-duration: 0.3s;
    box-shadow: 0 1px 1px rgba(0,0,0,.5);
    z-index: 99;
    
    &:after {
      opacity: 1;
      transform: translate3d(0, 0, 0) rotateZ(45deg);
    }
  }
}