#scrollTopBtn {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 55px;
  height: 55px;
  border-radius: 50%;
  border: 2px solid #000;
  background-color: #fff;
  color: #000;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transition: all 0.3s ease;
  z-index: 9999;
}

#scrollTopBtn:hover {
  background-color: #000;
  color: #fff;
}

#scrollTopBtn.show {
  opacity: 1;
  visibility: visible;
}