.back-to-toc {
  display: inline-block;
  margin: 20px 0;
  padding: 10px 20px;
  background-color: #3498db;
  color: white;
  text-decoration: none;
  border-radius: 5px;
  font-weight: bold;
  transition: background-color 0.3s ease;
}

.back-to-toc:hover {
  background-color: #2980b9;
}

.back-to-toc::before {
  content: "← ";
}

/* モバイル向け調整 */
@media (max-width: 768px) {
  .back-to-toc {
    display: block;
    text-align: center;
    margin: 15px auto;
    width: 80%;
    max-width: 250px;
  }
}