#scroll-top {
  position: fixed;
  bottom: 48px;
  right: 48px;
}

#scroll-top button {
  position: relative;
  overflow: hidden;
  height: 48px;
  width: 48px;
  border: none;
  outline: none;
  cursor: pointer;
  color: rgba(0, 0, 0, 0.3);
  font-size: 16px;
  background: #21c984;
  transition: width 0.5s;
  border-radius: 100px;
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.19), 0 6px 6px rgba(0, 0, 0, 0.23);
}

#scroll-top button span {
  display: inline-block;
  transition: opacity 0.3s ease 0s, transform 0.5s ease 0s;
  line-height: 48px;
  font-size: 20px;
  width: 100%;
}

#scroll-top button span::before {
  width: 100%;
  position: absolute;
  left: 0px;
  top: 200%;
  opacity: 0;
  content: attr(data-hover);
  -webkit-transform: translate3d(0, 0, 0);
  -moz-transform: translate3d(0, 0, 0);
  transform: translate3d(0, 0, 0);
  color: #fff;
  font-size: 16px;
  text-transform: uppercase;
}

#scroll-top:hover button {
  width: 120px;
  background: #9b59b6;
}

#scroll-top:hover button span {
  -webkit-transform: translateY(-200%);
  -moz-transform: translateY(-200%);
  transform: translateY(-200%);
}

#scroll-top:hover button span:before {
  opacity: 1;
}

#scroll-top button:active {
  background: #21c984;
}