:root {
  --primary-color: #2c3e50; /* Deep, trustworthy navy */
  --secondary-color: #f8f9fa; /* Soft, warm off-white */
  --accent-color: #1abc9c;   /* Hopeful teal */
  --accent-hover: #16a085;
  --text-color: #34495e;
  --light-gray: #ecf0f1;
  --white: #ffffff;
}

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  line-height: 1.6;
  color: var(--text-color);
  background-color: var(--secondary-color);
  padding: 0;
  margin: 0;
}

.back-button {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  margin: 1.5rem;
  color: var(--primary-color);
  text-decoration: none;
  font-weight: 500;
  border: 1px solid var(--primary-color);
  border-radius: 4px;
  transition: all 0.3s ease;
}

.back-button:hover {
  background-color: var(--primary-color);
  color: var(--white);
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1rem;
}

.section-title {
  text-align: center;
  color: var(--primary-color);
  margin-bottom: 2.5rem;
  font-size: 2.25rem;
}

.book-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 2rem;
  padding-bottom: 3rem;
}

.book-card {
  background: var(--white);
  border-radius: 8px;
  overflow: hidden;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.book-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
}

.book-card img {
  width: 100%;
  height: 200px;
  object-fit: cover;
}

.book-content {
  padding: 1.5rem;
}

.book-content h3 {
  margin-top: 0;
  color: var(--primary-color);
  font-size: 1.25rem;
}

.book-content p {
  color: var(--text-color);
  margin-bottom: 1.25rem;
}

.book-meta {
  display: flex;
  gap: 1rem;
  font-size: 0.875rem;
  color: var(--text-color);
  opacity: 0.8;
  margin-bottom: 1.5rem;
}

.btn-download {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  background-color: var(--accent-color);
  color: var(--white);
  text-decoration: none;
  border-radius: 4px;
  font-weight: 500;
  transition: background-color 0.3s ease;
}

.btn-download:hover {
  background-color: var(--accent-hover);
}

@media (max-width: 768px) {
  .book-grid {
    grid-template-columns: 1fr;
  }
  
  .section-title {
    font-size: 1.75rem;
  }
}