.yyui-ripple:before {
    content: "";
    position: absolute;
    left: 0;
    right: 0;
    top: 0;
    bottom: 0;
    margin: auto;
    min-width: 40px;
    width:100%;
    height: auto;
    border-radius: 50%;
    background: #aaa;
    opacity: 0;
}
.yyui-ripple.clicked:before {
    animation: ripple-click .5s ease-out 0s 1 alternate forwards;
}
@keyframes ripple-click {
    0% {
        transform: scale(1);
        opacity: .7;
    }
    100% {
        transform: scale(3);
        opacity: 0;
    }
}