#backToTop {
  position: fixed;
  bottom: 20px;
  right: 20px;
  background-color: #cde3fc7d;
  color: #ffffff64;
  border: none;
  border-radius: 50%;
  width: 50px;
  height: 50px;
  font-size: 18px;
  font-weight: bold;
  text-align: center;
  line-height: 50px;
  cursor: pointer;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  z-index: 1000;
  opacity: 0; /* 初始透明度 */
  visibility: hidden; 
  transition: opacity 0.3s ease, visibility 0.3s ease;
}

#backToTop.show {
  opacity: 1; /* 顯示時透明度為 1 */
  visibility: visible; /* 顯示時設定可見 */
}

#backToTop:hover {
  background-color: #150801;
  color: #fefefede;
  transform: scale(1.1);
}

@media (max-width: 768px) {
  #backToTop {
    width: 40px;
    height: 40px;
    font-size: 16px;
    line-height: 40px;
    bottom: 15px;
    right: 15px;
  }
}