body {
  margin: 0;
  font-family: 'Segoe UI', sans-serif;
  background: linear-gradient(135deg, #004C97, #FFD700);
  color: #000;
}
.header-img {
  width: 100%;
  max-height: 400px;
  object-fit: cover;
}
.nav {
  list-style: none;
  display: flex;
  justify-content: center;
  padding: 1rem;
  background: rgba(255, 255, 255, 0.9);
  box-shadow: 0 2px 5px rgba(0,0,0,0.2);
}
.nav li {
  margin: 0 1rem;
}
.nav a {
  text-decoration: none;
  color: #004C97;
  font-weight: bold;
}
.nav a:hover {
  color: #FFD700;
}
main {
  padding: 2rem;
}
.book-container a {
  display: inline-block;
  padding: 1rem 2rem;
  background-color: #004C97;
  color: white;
  border-radius: 12px;
  text-decoration: none;
  box-shadow: 0 4px 8px rgba(0,0,0,0.2);
  transition: background 0.3s;
}
.book-container a:hover {
  background-color: #003366;
}