.book-menu-tree .book-button {
  transition: background-color 0.3s, transform 0.3s;
}

.book-menu-tree .book-button:hover {
  background-color: #0056b3; /* Darker on hover */
  transform: translateY(-3px); /* Lift up */
  text-decoration: none;
}

.book-menu-tree .book-underline {
  width: 60px;
  height: 3px;
  background-color: #0d6efd; /* Bootstrap Primary */
  border-radius: 2px;
  margin-top: 8px;
}

.book-menu-tree .card:hover {
  box-shadow: 0 8px 16px rgba(0,0,0,0.15);
  transition: box-shadow 0.3s ease-in-out;
}