.book-container {
  position: relative;
  max-width: 1000px;
  margin: auto;
  perspective: 1500px;
  transition: height 0.3s ease;
  overflow: hidden;
  min-height: 400px; /* wichtig: Mindesthöhe */
}
.book-page {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  background: white;
  padding: 20px;
  transform-origin: left;
  transform: rotateY(0deg);
  transition: transform 0.7s ease, opacity 0.7s ease, visibility 0.7s ease;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15); /* sanfter Schatten */
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  z-index: 0;
  border-radius: 8px;
  background: white;
  transform-style: preserve-3d;
  backface-visibility: hidden;
}
.book-page.active {
  position: relative;
  transform: rotateY(0deg);
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
  z-index: 2;
}
.book-page.prev {
  transform: rotateY(-180deg);
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  z-index: 1;
}

.next-btn,
.prev-btn {
  margin-top: 30px;
  padding: 10px 20px;
  font-weight: bold;
  border: none;
  background: #007bff;
  color: white;
  border-radius: 4px;
}

@media (max-width: 768px) {
  .content {
    max-height: unset;
  }

  .book-page {
    padding: 15px;
  }

  .next-btn,
  .prev-btn {
    width: 100%;
    margin-top: 20px;
  }
}