/* 回到顶部按钮 */
#back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 2.8rem;
  height: 2.8rem;
  background-color: #f0f0f0;
  border: 1px solid #e0e0e0;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  opacity: 0;
  transform: translateY(10px);
  transition: all 0.25s ease-in-out;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
  z-index: 1000;
}

#back-to-top:hover {
  background-color: #e8e8e8;
  border-color: #d0d0d0;
  transform: translateY(-1px);
  box-shadow: 0 3px 12px rgba(0, 0, 0, 0.1);
}

#back-to-top.show {
  opacity: 1;
  transform: translateY(0);
}

#back-to-top i {
  font-size: 1rem;
  color: #333333;
  margin-top: -1px;
}

.dark #back-to-top {
  background-color: #262626;
  border-color: #333333;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
}

.dark #back-to-top:hover {
  background-color: #2d2d2d;
  border-color: #404040;
  box-shadow: 0 3px 12px rgba(0, 0, 0, 0.3);
}

.dark #back-to-top i {
  color: #e0e0e0;
}

@media (max-width: 768px) {
  #back-to-top {
    bottom: 1.25rem;
    right: 1.25rem;
    width: 2.25rem;
    height: 2.25rem;
    border-radius: 6px;
  }

  #back-to-top i {
    font-size: 0.85rem;
  }
}