/* ── Typography ── */
:root {
  --md-text-font: "Inter", sans-serif;
  --md-code-font: "JetBrains Mono", monospace;
}

/* ── Hero Banner ── */
.hero {
  background: linear-gradient(135deg, #1e3a5f 0%, #2563eb 50%, #0ea5e9 100%);
  border-radius: 16px;
  padding: 64px 48px;
  margin-bottom: 32px;
  color: white;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='60' height='60'%3E%3Ccircle cx='30' cy='30' r='1' fill='rgba(255,255,255,.08)'/%3E%3C/svg%3E");
  pointer-events: none;
}

.hero h1 {
  font-size: 3rem;
  font-weight: 800;
  margin: 0 0 16px;
  line-height: 1.1;
  color: white !important;
}

.hero p {
  font-size: 1.25rem;
  opacity: .85;
  max-width: 600px;
  margin: 0 auto 32px;
}

.hero-badges {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

.hero-badge {
  background: rgba(255,255,255,.15);
  border: 1px solid rgba(255,255,255,.25);
  border-radius: 999px;
  padding: 6px 18px;
  font-size: .875rem;
  font-weight: 600;
  backdrop-filter: blur(8px);
}

/* ── Volume Cards ── */
.volume-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
  margin: 24px 0;
}

.volume-card {
  background: var(--md-default-bg-color);
  border: 1px solid var(--md-default-fg-color--lightest);
  border-radius: 12px;
  padding: 24px;
  transition: box-shadow .2s, transform .2s;
  text-decoration: none !important;
  display: block;
  color: inherit !important;
}

.volume-card:hover {
  box-shadow: 0 8px 24px rgba(0,0,0,.12);
  transform: translateY(-2px);
}

.volume-card .vol-number {
  font-size: .75rem;
  font-weight: 700;
  letter-spacing: .1em;
  text-transform: uppercase;
  color: var(--md-primary-fg-color);
  margin-bottom: 8px;
}

.volume-card h3 {
  font-size: 1.1rem;
  font-weight: 700;
  margin: 0 0 8px;
}

.volume-card p {
  font-size: .9rem;
  color: var(--md-default-fg-color--light);
  margin: 0;
}

/* ── Callout Chips ── */
.chip-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 16px 0;
}

.chip {
  background: var(--md-primary-fg-color--light);
  color: var(--md-primary-fg-color);
  border-radius: 999px;
  padding: 4px 14px;
  font-size: .8rem;
  font-weight: 600;
}

/* ── Learning Path ── */
.learning-path {
  display: flex;
  flex-direction: column;
  gap: 0;
  margin: 24px 0;
}

.path-step {
  display: flex;
  align-items: flex-start;
  gap: 16px;
  padding: 16px 0;
  border-left: 2px solid var(--md-primary-fg-color--light);
  padding-left: 24px;
  position: relative;
}

.path-step::before {
  content: "";
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--md-primary-fg-color);
  position: absolute;
  left: -7px;
  top: 22px;
  flex-shrink: 0;
}

.path-step:last-child {
  border-left-color: transparent;
}

.path-step .step-num {
  font-size: .75rem;
  font-weight: 700;
  color: var(--md-primary-fg-color);
  min-width: 24px;
}

/* ── Stat Tiles ── */
.stats-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 16px;
  margin: 24px 0;
}

.stat-tile {
  background: var(--md-default-bg-color);
  border: 1px solid var(--md-default-fg-color--lightest);
  border-radius: 12px;
  padding: 20px;
  text-align: center;
}

.stat-tile .stat-value {
  font-size: 2rem;
  font-weight: 800;
  color: var(--md-primary-fg-color);
  line-height: 1;
}

.stat-tile .stat-label {
  font-size: .8rem;
  color: var(--md-default-fg-color--light);
  margin-top: 4px;
}

/* ── Chapter header ── */
.chapter-meta {
  background: var(--md-code-bg-color);
  border-radius: 8px;
  padding: 16px 20px;
  margin-bottom: 24px;
  font-size: .875rem;
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
}

.chapter-meta span {
  display: flex;
  align-items: center;
  gap: 6px;
  color: var(--md-default-fg-color--light);
}

/* ── Equation labels ── */
.eq-label {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.eq-label .eq-num {
  font-size: .8rem;
  color: var(--md-default-fg-color--light);
  min-width: 40px;
  text-align: right;
}

/* ── Dark mode overrides ── */
[data-md-color-scheme="slate"] .hero {
  background: linear-gradient(135deg, #0f172a 0%, #1d4ed8 50%, #0284c7 100%);
}

[data-md-color-scheme="slate"] .volume-card {
  border-color: rgba(255,255,255,.08);
}

[data-md-color-scheme="slate"] .volume-card:hover {
  box-shadow: 0 8px 24px rgba(0,0,0,.4);
}