.book-hero {
  padding: 2.5rem 2rem;
}

.book-hero__layout {
  display: grid;
  gap: 2rem;
  align-items: center;
}

@media (min-width: 768px) {
  .book-hero__layout {
    grid-template-columns: minmax(220px, 320px) minmax(0, 1fr);
    gap: 3rem;
  }
}

.book-cover {
  display: flex;
  justify-content: center;
  margin: 0 auto;
  max-width: 280px;
}

@media (min-width: 768px) {
  .book-cover {
    max-width: none;
    margin: 0;
    justify-content: flex-start;
  }
}

.book-cover__frame {
  position: relative;
  width: min(100%, 260px);
  max-height: min(68vh, 420px);
  border-radius: 4px 10px 10px 4px;
  overflow: hidden;
  background: #0f1f3d;
  box-shadow:
    0 2px 4px rgba(15, 31, 61, 0.12),
    0 12px 28px rgba(15, 31, 61, 0.18),
    4px 0 12px rgba(15, 31, 61, 0.08);
  transform: perspective(900px) rotateY(-4deg);
  transition: transform 0.25s ease, box-shadow 0.25s ease;
}

@media (min-width: 768px) {
  .book-cover__frame {
    width: min(100%, 300px);
  }
}

.book-cover__frame:hover {
  transform: perspective(900px) rotateY(0deg);
  box-shadow:
    0 4px 8px rgba(15, 31, 61, 0.14),
    0 20px 40px rgba(15, 31, 61, 0.22);
}

.book-cover__frame::before {
  content: "";
  position: absolute;
  inset: 0 auto 0 0;
  width: 6px;
  z-index: 1;
  background: linear-gradient(
    to right,
    rgba(0, 0, 0, 0.35),
    rgba(255, 255, 255, 0.08) 40%,
    transparent
  );
  pointer-events: none;
}

.book-cover__frame img {
  display: block;
  width: 100%;
  height: auto;
  max-height: min(68vh, 420px);
  object-fit: contain;
  object-position: center center;
}

.book-hero__content {
  text-align: center;
}

@media (min-width: 768px) {
  .book-hero__content {
    text-align: left;
  }
}

.book-title {
  font-size: clamp(1.5rem, 2.8vw, 2.15rem);
  margin-bottom: 0.5rem;
  line-height: 1.2;
}

.book-subtitle {
  margin: 0 0 0.85rem;
  font-size: 1.05rem;
  color: var(--sk-link);
  font-weight: 500;
  line-height: 1.45;
}

.book-tagline {
  margin: 0 0 1.25rem;
  font-size: 0.95rem;
  font-style: italic;
  color: var(--sk-muted);
  letter-spacing: 0.02em;
}

.book-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  justify-content: center;
}

@media (min-width: 768px) {
  .book-chips {
    justify-content: flex-start;
  }
}

.book-chip {
  display: inline-block;
  padding: 0.35rem 0.75rem;
  border-radius: 999px;
  font-size: 0.78rem;
  font-weight: 600;
  background: var(--sk-surface-muted);
  border: 1px solid var(--sk-border);
  color: var(--sk-muted);
}

.book-hero__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 1.5rem;
  justify-content: center;
}

@media (min-width: 768px) {
  .book-hero__actions {
    justify-content: flex-start;
  }
}

.section-intro {
  margin: -0.5rem 0 1.25rem;
}

.book-framework,
.book-audience {
  display: grid;
  gap: 1rem;
}

@media (min-width: 640px) {
  .book-framework {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .book-audience {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (min-width: 960px) {
  .book-framework {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

.book-framework__item,
.book-audience__item {
  padding: 1.25rem;
  background: var(--sk-surface);
  border: 1px solid var(--sk-border);
  border-radius: 12px;
}

.book-framework__item h3,
.book-audience__item h3 {
  margin: 0 0 0.35rem;
  font-size: 1.1rem;
}

.book-framework__item p,
.book-audience__item p {
  margin: 0;
  color: var(--sk-muted);
  font-size: 0.92rem;
}

.book-download {
  padding: 2rem;
}

.book-download__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 1.25rem 0;
}

.book-feedback {
  margin: 0 0 1.5rem;
}

.book-citation {
  margin: 0 0 1rem;
  padding: 1.25rem 1.5rem;
  background: var(--sk-surface-muted);
  border-left: 3px solid var(--sk-primary);
  border-radius: 0 8px 8px 0;
}

.book-citation p {
  margin: 0;
  font-size: 0.92rem;
  color: var(--sk-muted);
  line-height: 1.55;
}

.book-footer-tagline {
  margin: 0;
  font-size: 0.88rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--sk-link);
}

@media (max-width: 767px) {
  .book-hero,
  .book-download {
    padding: 1.75rem 1.25rem;
  }

  .book-cover__frame {
    transform: none;
    max-height: 360px;
  }

  .book-cover__frame:hover {
    transform: none;
  }
}