.back-btn {
  display: inline-block;
  padding: 12px 24px;
  font-size: 1rem;
  color: #ffffff;
  background: linear-gradient(to bottom, #87ceeb, #00008b);
  text-decoration: none;
  border-radius: 25px;
  transition: all 0.3s ease;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
  margin-bottom: 20px;
}

.back-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.3);
  background: linear-gradient(to bottom, #6a9eda, #00006a);
}

.chapters-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 2rem;
  padding: 2rem;
  perspective: 1000px;
}

.chapter-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 2rem 1rem;
  font-size: 1.1rem;
  font-weight: 600;
  color: #ffffff;
  text-decoration: none;
  text-align: center;
  border-radius: 15px;
  background: linear-gradient(to bottom, #87ceeb, #00008b);
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.2), 0 6px 6px rgba(0, 0, 0, 0.2);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
  position: relative;
  overflow: hidden;
  border: none;
  cursor: pointer;
}

.chapter-btn h2,
.chapter-btn h4,
.chapter-btn h5,
.chapter-btn h6,
.chapter-btn marquee {
  margin: 0;
  color: #ffffff;
  text-shadow: 1px 1px 3px rgba(0, 0, 0, 0.3);
}

.chapter-btn:hover {
  transform: translateY(-5px) scale(1.03);
  box-shadow: 0 15px 30px rgba(0, 0, 0, 0.3), 0 10px 10px rgba(0, 0, 0, 0.25);
  background: linear-gradient(to bottom, #6a9eda, #00006a);
}

.chapter-btn::after {
  content: "";
  position: absolute;
  top: 50%;
  left: 50%;
  width: 5px;
  height: 5px;
  background: rgba(0, 0, 0, 0.1);
  border-radius: 50%;
  transform: scale(0) translate(-50%, -50%);
  transition: width 0.5s ease, height 0.5s ease, opacity 0.5s ease;
  opacity: 0;
}

.chapter-btn:hover::after {
  left: 100%;
}

.chapter-btn:active {
  background: linear-gradient(to bottom, #003399, #000d26);
  box-shadow: inset 0 5px 8px rgba(0, 0, 0, 0.6), 0 2px 5px rgba(0, 0, 0, 0.3);
  transform: translateY(2px);
}

/* Submenu Styling */
.submenu-container {
  cursor: pointer;
  position: relative;
}

.submenu-arrow {
  position: absolute;
  right: 1rem;
  top: 50%;
  transform: translateY(-50%);
  transition: transform 0.3s ease;
  font-size: 1.2rem;
}

.submenu-container.active .submenu-arrow {
  transform: translateY(-50%) rotate(180deg);
}

.submenu {
  grid-column: 1 / -1;
  display: none;
  background: rgba(255, 255, 255, 0.1);
  border-radius: 10px;
  padding: 1rem;
  margin-top: 0.5rem;
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(255, 255, 255, 0.2);
}

.submenu.active {
  display: block;
}

.submenu-item {
  display: flex;
  align-items: center;
  padding: 0.8rem 1rem;
  margin: 0.5rem 0;
  background: rgba(255, 255, 255, 0.1);
  border-radius: 8px;
  color: #ffffff;
  text-decoration: none;
  transition: all 0.3s ease;
  border: 1px solid rgba(255, 255, 255, 0.1);
}

.submenu-item:hover {
  background: rgba(255, 255, 255, 0.2);
  transform: translateX(5px);
  border-color: rgba(255, 255, 255, 0.3);
}

.submenu-item i {
  margin-right: 0.8rem;
  font-size: 1.1rem;
  color: #ff6b6b;
}

.submenu-item span {
  font-weight: 500;
  font-size: 0.95rem;
}

/* Section Divider Styling */
.section-divider {
  grid-column: 1 / -1;
  text-align: center;
  margin: 3rem 0 2rem 0;
  padding: 1rem;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  border-radius: 15px;
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
}

.section-divider h2 {
  color: #ffffff;
  font-size: 2rem;
  margin: 0;
  text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
  font-weight: 600;
}

/* Coming Soon Styling */
.coming-soon {
  display: inline-block;
  animation: pulse 2s infinite;
  font-weight: bold;
  color: #ffeb3b;
  text-shadow: 1px 1px 2px rgba(0, 0, 0, 0.5);
}

@keyframes pulse {
  0% {
    opacity: 1;
  }
  50% {
    opacity: 0.5;
  }
  100% {
    opacity: 1;
  }
}

/* Coming Soon Page Styling */
.chapters-grid .coming-soon {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 3rem 2rem;
  text-align: center;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  border-radius: 15px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
}

.coming-soon i {
  font-size: 3rem;
  margin-bottom: 1rem;
  opacity: 0.8;
}

.coming-soon h2 {
  font-size: 2rem;
  margin-bottom: 1rem;
  text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
}

.coming-soon p {
  font-size: 1.1rem;
  opacity: 0.9;
  max-width: 400px;
  line-height: 1.6;
}

@media screen and (max-width: 768px) {
  .chapters-grid {
    grid-template-columns: 1fr;
    gap: 1.2rem;
    padding: 1rem;
  }

  .chapter-btn {
    padding: 1.5rem;
    font-size: 1rem;
  }

  .chapter-btn h2 {
    font-size: 1.2em;
    margin-bottom: 0.3rem;
  }

  .chapter-btn h4,
  .chapter-btn h5,
  .chapter-btn h6 {
    font-size: 0.9em;
  }

  .back-btn {
    padding: 0.4rem 0.8rem;
    font-size: 0.9rem;
  }

  .chapters-grid .coming-soon {
    padding: 2rem 1rem;
  }

  .coming-soon i {
    font-size: 2.5rem;
  }

  .coming-soon h2 {
    font-size: 1.5rem;
  }

  .coming-soon p {
    font-size: 1rem;
  }
}