#backToTop {
  width: 50px;
  height: 50px;
  padding: 0;
  display: flex;
  align-items: center;
  justify-content: center;

  opacity: 0;
  transform: translateY(20px);
  visibility: hidden;
  transition: opacity 0.4s ease, transform 0.4s ease;

  position: fixed;
  bottom: 40px;
  right: 40px;
  z-index: 100;
  background-color: red;
  color: white;
  border: none;
  border-radius: 50%;
  cursor: pointer;
  font-size: 20px;
  box-shadow: 0 4px 6px rgba(0,0,0,0.3);
}

#backToTop.show {
  opacity: 1;
  transform: translateY(0);
  visibility: visible;
}

#backToTop:hover {
  background-color: darkred;
}
@keyframes pulse {
  0% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.15);
  }
  100% {
    transform: scale(1);
  }
}

#backToTop.pulsing {
  animation: pulse 0.3s ease;
}