.to-top-btn {
  position: fixed;
  bottom: 20px;
  right: 20px;
  width: 70px;
  height: 70px;
  border: none;
  border-radius: 50%;
  background-color: rgba(255, 255, 255, 0.9);
  box-shadow: 0 0 5px rgba(0, 0, 0, 0.17);
  font-size: 22px;
  font-weight: 700;
  color: #333333;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s ease, visibility 0.3s ease, box-shadow 0.9s ease,
    background 0.9s ease;
  z-index: 999;
}

.to-top-btn:hover {
  background-color: #ffffffcc;
  box-shadow: 0 0 25px rgba(0, 0, 0, 0.17);
}

.to-top-btn.active {
  opacity: 1;
  visibility: visible;
}