/* Reset */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Inter', sans-serif;
}

body {
  background: #ffffff;
  color: #333;
  font-size: 16px;
  line-height: 1.6;
}

/* Navbar */
.navbar {
  background: #007BFF;
  padding: 1rem 2rem;
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.navbar .logo {
  text-decoration: none;
  color: white;
  font-size: 1rem;
  font-weight: bold;
}

.navbar h1 {
  margin: 0;
  display: inline-block;
  cursor: pointer;
}

/* Header */
header {
  background: #f7f9fc;
  padding: 2rem 2rem;
  text-align: center;
  border-bottom: 2px solid #e6e6e6;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
  margin-bottom: 3rem;
}

header .container h1 {
  font-size: 2.5rem;
  color: #0056b3;
  margin-bottom: 0.5rem;
}

header .container p {
  font-size: 1.1rem;
  color: #666;
  margin-bottom: 1.5rem;
}

/* Main Content */
main {
  max-width: 1200px;
  margin: 3rem auto;
  padding: 0 2rem;
}

.chapters h2 {
  display: grid;
  font-size: 2rem;
  color: #007BFF;
  margin-bottom: 1.5rem;
  animation: fadeUp 1s ease-out;
}

.chapter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 2rem;
  margin-bottom: 3rem;
}

.chapter-card {
  display: block;
  background: #f0f8ff;
  padding: 1.5rem;
  text-align: center;
  border-radius: 10px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
  font-weight: 600;
  font-size: 1.1rem;
  color: #0056b3;
  text-decoration: none;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.chapter-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 18px rgba(0, 0, 0, 0.2);
}

.chapter-card:active {
  transform: translateY(2px);
}

/* Footer */
footer {
  background: #f0f0f0;
  padding: 1.5rem 2rem;
  text-align: center;
  margin-top: 4rem;
  font-size: 1rem;
  color: #666;
  border-top: 2px solid #e6e6e6;
}

footer p {
  margin: 0;
}

/* Animations */
@keyframes fadeUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Responsive Design */
@media (max-width: 768px) {
  header .container h1 {
    font-size: 2rem;
  }

  header .container p {
    font-size: 1rem;
  }

  .chapter-grid {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  .chapter-card {
    font-size: 1rem;
    padding: 1.2rem;
  }
}