:root {
  --bg-primary: #f8f9fb;
  --bg-secondary: #ffffff;
  --text-primary: #212227;
  --border-color: #d8dce3;
  --accent: #4b8cc8;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Segoe UI", Arial, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
}

.page-shell {
  max-width: 1200px;
  margin: 0 auto;
  padding: 64px 20px;
}

.hero {
  border-left: 8px solid var(--accent);
  padding-left: 24px;
  margin-bottom: 48px;
}

.hero h1 {
  margin: 0;
  font-size: clamp(2.2rem, 7vw, 4rem);
  line-height: 0.9;
  text-transform: uppercase;
  letter-spacing: -0.03em;
  font-weight: 900;
}

.hero h1 span {
  display: inline-block;
  margin-top: 8px;
}

.hero p {
  margin: 16px 0 0;
  max-width: 640px;
  font-size: 1.1rem;
  opacity: 0.75;
}

.books-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 28px;
}

.book-card {
  display: flex;
  flex-direction: column;
  text-decoration: none;
  color: inherit;
  border: 1px solid var(--border-color);
  background: var(--bg-secondary);
  transition: border-color 0.3s ease, transform 0.3s ease;
}

.book-card:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
}

.book-cover {
  width: 100%;
  aspect-ratio: 3 / 4;
  object-fit: cover;
  filter: grayscale(100%);
  transition: transform 0.4s ease, filter 0.4s ease;
}

.book-card:hover .book-cover {
  filter: grayscale(0);
  transform: scale(1.04);
}

.book-card-body {
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 16px;
  min-height: 260px;
}

.book-meta {
  display: flex;
  justify-content: space-between;
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.book-author {
  font-weight: 800;
  color: var(--accent);
}

.book-year {
  opacity: 0.55;
  font-weight: 700;
}

.book-title {
  margin: 0;
  font-size: 1.6rem;
  line-height: 1.08;
  text-transform: uppercase;
  font-weight: 900;
}

.book-description {
  margin: 0;
  font-size: 0.95rem;
  line-height: 1.6;
  opacity: 0.78;
  flex-grow: 1;
}

.book-cta {
  display: inline-block;
  align-self: flex-start;
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  font-weight: 900;
  border-bottom: 2px solid var(--accent);
  padding-bottom: 4px;
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 36px;
  color: var(--accent);
  text-decoration: none;
  font-size: 0.74rem;
  font-weight: 900;
  text-transform: uppercase;
  letter-spacing: 0.2em;
}

.back-link:hover {
  color: var(--text-primary);
}

.arrow {
  font-size: 1.15rem;
}

.book-detail-layout {
  display: grid;
  grid-template-columns: minmax(280px, 360px) 1fr;
  gap: 48px;
}

.book-side-panel {
  background: #212227;
  color: #fff;
  padding: 22px;
}

.book-side-panel h4 {
  margin: 0 0 4px;
  font-size: 0.65rem;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--accent);
}

.book-side-panel p {
  margin: 0 0 16px;
  font-weight: 700;
}

.download-btn {
  width: 100%;
  border: 0;
  background: var(--accent);
  color: #fff;
  padding: 14px 16px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  font-weight: 900;
}

.book-detail-content h1 {
  margin: 0 0 16px;
  font-size: clamp(2rem, 6vw, 4.6rem);
  text-transform: uppercase;
  line-height: 0.92;
}

.title-accent {
  width: 92px;
  height: 8px;
  background: var(--accent);
  margin-bottom: 24px;
}

.lead-quote {
  border-left: 4px solid var(--accent);
  padding-left: 18px;
  font-size: 1.4rem;
  font-style: italic;
  font-weight: 700;
}

.toc-title {
  margin: 34px 0 16px;
  font-size: 1.8rem;
  text-transform: uppercase;
  font-weight: 900;
}

.toc-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.toc-list li {
  display: flex;
  gap: 10px;
  border-bottom: 1px solid var(--border-color);
  padding: 10px 0;
  font-weight: 700;
}

.toc-list span {
  color: var(--accent);
  font-weight: 900;
}

.big-quote {
  margin-top: 36px;
  border-left: 8px solid var(--accent);
  padding: 18px 20px;
  background: var(--bg-secondary);
  font-size: 1.8rem;
  font-style: italic;
  font-weight: 700;
}

@media (max-width: 900px) {
  .book-detail-layout {
    grid-template-columns: 1fr;
  }
}