Material Design ripple effect Sass mixin

ripple.scss

@mixin ripple($color: rgba(#fff, .2)) {
  position: relative;
  overflow: hidden;

  &::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 5px;
    height: 5px;
    background: $color;
    opacity: 0;
    border-radius: 100%;
    transform: scale(1, 1) translate(-50%);
    transform-origin: 50% 50%;
    transition: .3s;
  }

  &:focus::after {
    animation: ripple .7s ease-out;
  }
}

@keyframes ripple {
  0% {
    transform: scale(0, 0);
    opacity: 1;
  }
  20% {
    transform: scale(25, 25);
    opacity: 1;
  }
  100% {
    opacity: 0;
    transform: scale(40, 40);
  }
}