.chapters-shell {
  background: var(--page-bg);
}

.chapters-main {
  width: min(72rem, calc(100% - 2.5rem));
  margin: 0 auto;
  padding: 3rem 0 4.75rem;
}

.chapters-hero {
  width: min(48rem, 100%);
  margin-bottom: 3rem;
}

.chapters-hero h1 {
  margin: 0;
  font-family: "Manrope", "Inter", sans-serif;
  font-size: clamp(2.2rem, 4vw, 2.75rem);
  font-weight: 700;
  line-height: 1.15;
  letter-spacing: -0.02em;
  color: var(--text);
}

.chapters-intro {
  max-width: 46rem;
  margin: 1rem 0 0;
  color: var(--text-muted);
  font-size: 1.125rem;
  line-height: 1.7;
}

.chapters-sections {
  display: grid;
  gap: 2rem;
}

.chapter-library-section {
  display: grid;
  gap: 1rem;
}

.chapter-library-heading h2 {
  margin: 0;
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 1.25rem;
  font-weight: 500;
  line-height: 1.35;
  color: var(--ink-primary);
}

.chapter-library-list {
  display: grid;
  gap: 1rem;
}

.chapter-card {
  display: grid;
  gap: 0;
  padding: 1.5rem;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: var(--surface);
  box-shadow: 0 1px 2px rgba(15, 23, 42, 0.04);
  text-decoration: none;
  transition: transform 140ms ease, box-shadow 140ms ease, border-color 140ms ease;
}

.chapter-card:hover,
.chapter-card:focus-visible {
  transform: translateY(-2px);
  border-color: rgba(43, 91, 166, 0.18);
  box-shadow: 0 10px 24px rgba(15, 23, 42, 0.08);
}

.chapter-card-header {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 0.7rem;
}

.chapter-card-number {
  font-size: 0.82rem;
  line-height: 1.2;
}

.chapter-card-number {
  color: var(--brand-blue);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.chapter-card-status {
  display: inline-flex;
  flex: 0 0 auto;
  width: 1rem;
  height: 1rem;
  color: #16a34a;
}

.chapter-card-body {
  display: grid;
  gap: 0.65rem;
  margin-bottom: 1rem;
}

.chapter-card-reading {
  position: relative;
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  color: var(--text-muted);
  font-size: 0.8rem;
  font-weight: 500;
  line-height: 1.2;
  cursor: help;
}

.chapter-card-reading-icon {
  display: inline-flex;
  flex: 0 0 auto;
  width: 1.1rem;
  height: 1.1rem;
}

.chapter-card-reading::before,
.chapter-card-reading::after {
  position: absolute;
  left: 0;
  opacity: 0;
  pointer-events: none;
  transform: translateY(0.25rem);
  transition: opacity 140ms ease, transform 140ms ease;
  z-index: 2;
}

.chapter-card-reading::before {
  content: "";
  top: calc(100% + 0.2rem);
  border-width: 0 0.45rem 0.45rem;
  border-style: solid;
  border-color: transparent transparent rgba(15, 23, 42, 0.92);
}

.chapter-card-reading::after {
  content: attr(data-tooltip);
  top: calc(100% + 0.6rem);
  min-width: 16rem;
  max-width: min(26rem, 80vw);
  padding: 0.75rem 0.85rem;
  border-radius: 0.5rem;
  background: rgba(15, 23, 42, 0.92);
  color: #f8fafc;
  font-size: 0.78rem;
  font-weight: 400;
  line-height: 1.55;
  box-shadow: 0 16px 32px rgba(15, 23, 42, 0.2);
  white-space: normal;
}

.chapter-card-reading:hover::before,
.chapter-card-reading:hover::after,
.chapter-card:focus-visible .chapter-card-reading::before,
.chapter-card:focus-visible .chapter-card-reading::after {
  opacity: 1;
  transform: translateY(0);
}

.chapter-card h3 {
  margin: 0;
  color: var(--text);
  font-size: 1.5rem;
  font-weight: 500;
  line-height: 1.25;
  letter-spacing: -0.02em;
  transition: color 140ms ease;
}

.chapter-card:hover h3,
.chapter-card:focus-visible h3 {
  color: var(--brand-blue);
}

.chapter-card p {
  margin: 0;
  color: var(--text-muted);
  font-size: 0.95rem;
  line-height: 1.7;
}

.chapter-card-tags {
  display: flex;
  gap: 0.55rem;
  flex-wrap: wrap;
}

.chapter-card-footer {
  display: flex;
  align-items: center;
  gap: 0.75rem 0.9rem;
  flex-wrap: wrap;
}

.chapter-card-tag {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  min-height: 1.9rem;
  padding: 0.28rem 0.7rem;
  border-radius: 0.375rem;
  background: var(--surface-muted);
  color: var(--text);
  font-size: 0.78rem;
  font-weight: 500;
}

.chapter-card-tag-icon {
  display: inline-flex;
  flex: 0 0 auto;
  width: 0.95rem;
  height: 0.95rem;
  color: var(--text-muted);
}

.chapter-card-status svg {
  display: block;
  width: 1rem;
  height: 1rem;
}

.chapter-card-reading-icon svg {
  display: block;
  width: 1.1rem;
  height: 1.1rem;
}

.chapter-card-tag-icon svg {
  display: block;
  width: 0.95rem;
  height: 0.95rem;
}

.additional-resources {
  margin-top: 4rem;
  padding: 1.5rem;
  border-radius: 0.5rem;
  background: var(--surface-muted);
}

.additional-resources h3 {
  margin: 0 0 1rem;
  color: var(--text);
  font-size: 1.125rem;
  font-weight: 500;
}

.additional-resources-grid {
  display: grid;
  gap: 1rem;
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.additional-resource-card {
  display: grid;
  gap: 0.35rem;
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 0.375rem;
  background: var(--surface);
  color: inherit;
  text-decoration: none;
  transition: box-shadow 140ms ease, transform 140ms ease, border-color 140ms ease;
}

.additional-resource-card:hover,
.additional-resource-card:focus-visible {
  transform: translateY(-1px);
  border-color: rgba(43, 91, 166, 0.18);
  box-shadow: 0 10px 20px rgba(15, 23, 42, 0.06);
}

.additional-resource-title {
  color: var(--text);
  font-size: 0.95rem;
  font-weight: 500;
}

.additional-resource-card p {
  margin: 0;
  color: var(--text-muted);
  font-size: 0.78rem;
  line-height: 1.6;
}

@media (max-width: 980px) {
  .chapters-main {
    padding-top: 3rem;
  }

  .additional-resources-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 640px) {
  .chapters-main {
    width: min(100% - 2rem, 76rem);
    padding: 3rem 0 4rem;
  }

  .chapters-hero h1 {
    font-size: 2.2rem;
  }

  .chapter-card {
    padding: 1.5rem;
  }

  .chapter-card h3 {
    font-size: 1.3rem;
  }

  .chapter-card p {
    font-size: 0.92rem;
  }

  .chapter-card-reading::after {
    min-width: 13rem;
    max-width: min(20rem, calc(100vw - 3rem));
  }
}