Animated CSS Gradient Complete

button-animated.less

.button {
  background-size: 100%;
  background-image: linear-gradient(#fff, #ccc);
  border-radius: 0.45rem;
  border: 1px solid #ddd;
  cursor: pointer;
  color: #333;
  display: inline-block;
  font-size: 1.25rem;
  font-weight: 300;
  padding: 1rem 1.5rem;
  position: relative;
  z-index: 100;
  
  &:before {
    border-radius: inherit;
    background-image: linear-gradient(#ccc, #fff);
    content: '';    
    display: block;
    height: 100%;
    position: absolute;
    top: 0; left: 0;
    opacity: 0;
    width: 100%;
    z-index: -100;
    transition: opacity 0.45s;
  }
  
  &:hover {
    &:before {
      opacity: 1;
    }
  }
}