.w3-btn.w3-ripple {position:relative;overflow:hidden}
.w3-btn.w3-ripple:after {content:"";background:#90EE90;display:block;position:absolute;padding-top:250%;padding-left:250%;margin-left:-20px !important;margin-top:-100%;opacity:0;transition:all 1s}
.w3-btn.w3-ripple:active:after {padding:0;margin:0;opacity:1;transition:0s}