/* ========== Design tokens ========== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --bg: #f6f4f0;
  --bg-card: #fffcf7;
  --bg-tint: #efebe3;
  --text: #1c1917;
  --text-soft: #57534e;
  --text-faint: #a8a29e;
  --line: #e7e2d9;
  --accent: #0d9488;
  --accent-deep: #0f766e;
  --accent-soft: #ccfbf1;
  --gold: #b45309;
  --gold-soft: #fef3c7;
  --radius: 16px;
  --radius-sm: 10px;
  --shadow: 0 1px 2px rgba(28,25,23,0.04), 0 8px 24px rgba(28,25,23,0.04);
  --shadow-lift: 0 4px 20px rgba(28,25,23,0.08);
  --font: 'DM Sans', system-ui, sans-serif;
  --serif: 'Instrument Serif', Georgia, serif;
}

[data-theme="dark"] {
  --bg: #0c0b0a;
  --bg-card: #161412;
  --bg-tint: #121110;
  --text: #f5f5f4;
  --text-soft: #a8a29e;
  --text-faint: #57534e;
  --line: #292524;
  --accent: #2dd4bf;
  --accent-deep: #5eead4;
  --accent-soft: #134e4a;
  --gold: #fbbf24;
  --gold-soft: #422006;
  --shadow: 0 1px 2px rgba(0,0,0,0.3), 0 8px 24px rgba(0,0,0,0.25);
  --shadow-lift: 0 8px 32px rgba(0,0,0,0.4);
}

html { scroll-behavior: smooth; }

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
  min-height: 100vh;
  transition: background 0.3s ease, color 0.3s ease;
  overflow-x: hidden;
}

a { color: inherit; text-decoration: none; }

.container {
  width: 100%;
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ========== Ambient maths field ========== */
.ambient {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  overflow: hidden;
}

/* Soft colour orbs — slow drift */
.orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(80px);
  will-change: transform;
}

.orb-1 {
  width: 480px;
  height: 480px;
  background: var(--accent);
  top: -140px;
  right: -100px;
  opacity: 0.11;
  animation: orbDrift1 28s ease-in-out infinite alternate;
}

.orb-2 {
  width: 380px;
  height: 380px;
  background: var(--gold);
  bottom: 18%;
  left: -120px;
  opacity: 0.07;
  animation: orbDrift2 34s ease-in-out infinite alternate;
}

.orb-3 {
  width: 280px;
  height: 280px;
  background: var(--accent);
  bottom: -60px;
  right: 15%;
  opacity: 0.06;
  animation: orbDrift3 22s ease-in-out infinite alternate;
}

[data-theme="dark"] .orb-1 { opacity: 0.07; }
[data-theme="dark"] .orb-2 { opacity: 0.05; }
[data-theme="dark"] .orb-3 { opacity: 0.04; }

@keyframes orbDrift1 {
  0%   { transform: translate(0, 0) scale(1); }
  100% { transform: translate(-40px, 50px) scale(1.08); }
}
@keyframes orbDrift2 {
  0%   { transform: translate(0, 0) scale(1); }
  100% { transform: translate(55px, -35px) scale(1.12); }
}
@keyframes orbDrift3 {
  0%   { transform: translate(0, 0) scale(1); }
  100% { transform: translate(-30px, -45px) scale(0.92); }
}

/* Faint coordinate grid (fades toward edges) */
.math-grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(color-mix(in srgb, var(--text) 6%, transparent) 1px, transparent 1px),
    linear-gradient(90deg, color-mix(in srgb, var(--text) 6%, transparent) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: radial-gradient(ellipse 75% 65% at 50% 28%, black 15%, transparent 72%);
  -webkit-mask-image: radial-gradient(ellipse 75% 65% at 50% 28%, black 15%, transparent 72%);
  opacity: 0.5;
  animation: gridPulse 12s ease-in-out infinite alternate;
}

[data-theme="dark"] .math-grid {
  opacity: 0.32;
  background-image:
    linear-gradient(color-mix(in srgb, var(--text) 11%, transparent) 1px, transparent 1px),
    linear-gradient(90deg, color-mix(in srgb, var(--text) 11%, transparent) 1px, transparent 1px);
}

@keyframes gridPulse {
  0%   { opacity: 0.4; }
  100% { opacity: 0.58; }
}
[data-theme="dark"] .math-grid {
  animation-name: gridPulseDark;
}
@keyframes gridPulseDark {
  0%   { opacity: 0.26; }
  100% { opacity: 0.4; }
}

/* Floating maths symbols */
.math-symbols {
  position: absolute;
  inset: 0;
  font-family: var(--serif);
  color: var(--text);
  user-select: none;
}

.math-sym {
  position: absolute;
  font-style: italic;
  line-height: 1;
  opacity: 0.07;
  will-change: transform, opacity;
}

[data-theme="dark"] .math-sym {
  opacity: 0.095;
}

/* Base positions + staggered float animations */
.math-sym.s1  { font-size: 3.2rem; top: 8%;  left: 5%;  animation: floatA 18s ease-in-out infinite; }
.math-sym.s2  { font-size: 2.4rem; top: 14%; right: 11%; opacity: 0.055; animation: floatB 22s ease-in-out infinite 1.2s; }
.math-sym.s3  { font-size: 4.4rem; top: 40%; left: 2%;  animation: floatC 26s ease-in-out infinite 0.5s; }
.math-sym.s4  { font-size: 2rem;   top: 26%; left: 20%; opacity: 0.05; animation: floatA 20s ease-in-out infinite 2s; }
.math-sym.s5  { font-size: 3.5rem; top: 16%; right: 26%; animation: floatB 24s ease-in-out infinite 0.8s; }
.math-sym.s6  { font-size: 2.7rem; bottom: 26%; right: 7%; animation: floatC 19s ease-in-out infinite 1.5s; }
.math-sym.s7  { font-size: 4.8rem; bottom: 10%; left: 16%; opacity: 0.048; animation: floatA 28s ease-in-out infinite 0.3s; }
.math-sym.s8  { font-size: 2.1rem; top: 52%;  right: 20%; animation: floatB 21s ease-in-out infinite 2.4s; }
.math-sym.s9  { font-size: 2.9rem; top: 66%;  left: 7%;  animation: floatC 23s ease-in-out infinite 1s; }
.math-sym.s10 { font-size: 2.5rem; top: 7%;   left: 46%; opacity: 0.05; animation: floatA 17s ease-in-out infinite 3s; }
.math-sym.s11 { font-size: 3.3rem; bottom: 20%; left: 40%; animation: floatB 25s ease-in-out infinite 0.6s; }
.math-sym.s12 { font-size: 1.9rem; top: 36%;  right: 5%;  opacity: 0.055; animation: floatC 16s ease-in-out infinite 2.8s; }
.math-sym.s13 { font-size: 2.4rem; bottom: 7%;  right: 32%; animation: floatA 20s ease-in-out infinite 1.8s; }
.math-sym.s14 { font-size: 3.8rem; top: 70%;  right: 12%; opacity: 0.045; animation: floatB 27s ease-in-out infinite 0.4s; }

[data-theme="dark"] .math-sym.s2,
[data-theme="dark"] .math-sym.s4,
[data-theme="dark"] .math-sym.s7,
[data-theme="dark"] .math-sym.s10,
[data-theme="dark"] .math-sym.s14 { opacity: 0.075; }

/* Three float patterns: vertical + slight rotate, diagonal, horizontal sway */
@keyframes floatA {
  0%, 100% { transform: translate(0, 0) rotate(-8deg); }
  33%      { transform: translate(12px, -18px) rotate(-14deg); }
  66%      { transform: translate(-8px, 10px) rotate(-4deg); }
}
@keyframes floatB {
  0%, 100% { transform: translate(0, 0) rotate(6deg); }
  40%      { transform: translate(-16px, -12px) rotate(12deg); }
  70%      { transform: translate(10px, 16px) rotate(2deg); }
}
@keyframes floatC {
  0%, 100% { transform: translate(0, 0) rotate(4deg); }
  25%      { transform: translate(14px, 8px) rotate(-2deg); }
  50%      { transform: translate(-6px, -20px) rotate(10deg); }
  75%      { transform: translate(-12px, 6px) rotate(0deg); }
}

/* Soft equation fragments — slow drift + opacity pulse */
.math-eq {
  position: absolute;
  font-family: var(--serif);
  font-size: 0.92rem;
  letter-spacing: 0.03em;
  color: var(--text);
  opacity: 0.042;
  white-space: nowrap;
  will-change: transform, opacity;
}

[data-theme="dark"] .math-eq { opacity: 0.055; }

.math-eq.e1 {
  top: 21%; left: 56%;
  animation: eqDrift 30s ease-in-out infinite, eqFade 8s ease-in-out infinite;
}
.math-eq.e2 {
  bottom: 30%; left: 26%;
  animation: eqDrift 36s ease-in-out infinite reverse, eqFade 10s ease-in-out infinite 2s;
}
.math-eq.e3 {
  top: 46%; right: 38%; font-size: 1rem;
  animation: eqDrift 32s ease-in-out infinite 1s, eqFade 9s ease-in-out infinite 4s;
}

@keyframes eqDrift {
  0%, 100% { transform: translate(0, 0) rotate(-3deg); }
  50%      { transform: translate(20px, -14px) rotate(2deg); }
}
@keyframes eqFade {
  0%, 100% { opacity: 0.03; }
  50%      { opacity: 0.07; }
}
[data-theme="dark"] .math-eq.e1,
[data-theme="dark"] .math-eq.e2,
[data-theme="dark"] .math-eq.e3 {
  animation-name: eqDrift, eqFadeDark;
}
@keyframes eqFadeDark {
  0%, 100% { opacity: 0.04; }
  50%      { opacity: 0.09; }
}

/* Content above ambient */
.header, .hero, .section, .footer {
  position: relative;
  z-index: 1;
}

/* Respect reduced motion */
@media (prefers-reduced-motion: reduce) {
  .orb, .math-sym, .math-eq, .math-grid {
    animation: none !important;
  }
}

/* ========== Header ========== */
.header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in srgb, var(--bg) 80%, transparent);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--line);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
  gap: 10px;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 6px;
  margin-left: auto;
  position: relative;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 1.15rem;
  letter-spacing: -0.03em;
}

.logo-mark {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  background: var(--accent);
  color: #fff;
  border-radius: 10px;
}

[data-theme="dark"] .logo-mark {
  color: #0c0b0a;
}

.nav {
  display: flex;
  align-items: center;
  gap: 2px;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.nav-link {
  padding: 7px 10px;
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--text-soft);
  border-radius: 8px;
  transition: color 0.15s, background 0.15s;
  white-space: nowrap;
}

.nav-link:hover,
.nav-link.active {
  color: var(--text);
  background: var(--bg-tint);
}

/* Mobile menu button — hidden on desktop */
.nav-toggle {
  display: none;
  margin-left: 6px;
  width: 42px;
  height: 42px;
  border: 1px solid var(--line);
  background: var(--bg-card);
  border-radius: 10px;
  cursor: pointer;
  align-items: center;
  justify-content: center;
  color: var(--text);
  flex-shrink: 0;
  transition: background 0.15s;
}

.nav-toggle:hover {
  background: var(--bg-tint);
}

.nav-toggle-icon {
  display: flex;
  flex-direction: column;
  gap: 5px;
  width: 18px;
}

.nav-toggle-icon span {
  display: block;
  height: 2px;
  width: 100%;
  background: currentColor;
  border-radius: 1px;
  transition: transform 0.2s, opacity 0.2s;
}

.nav-toggle[aria-expanded="true"] .nav-toggle-icon span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}
.nav-toggle[aria-expanded="true"] .nav-toggle-icon span:nth-child(2) {
  opacity: 0;
}
.nav-toggle[aria-expanded="true"] .nav-toggle-icon span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

.theme-toggle {
  margin-left: 6px;
  width: 38px;
  height: 38px;
  border: 1px solid var(--line);
  background: var(--bg-card);
  border-radius: 10px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-soft);
  transition: background 0.15s, color 0.15s;
}

.theme-toggle:hover {
  background: var(--bg-tint);
  color: var(--text);
}

[data-theme="dark"] .icon-sun { display: block; }
[data-theme="dark"] .icon-moon { display: none; }
:root:not([data-theme="dark"]) .icon-sun { display: none; }
:root:not([data-theme="dark"]) .icon-moon { display: block; }

/* ========== Hero ========== */
.hero {
  position: relative;
  z-index: 1;
  padding: 40px 0 28px;
}

.hero-row {
  display: grid;
  grid-template-columns: 1.3fr 0.9fr;
  gap: 28px 40px;
  align-items: start;
  margin-bottom: 24px;
}

.hero-content {
  max-width: 520px;
  margin-bottom: 0;
}

.hero-side {
  display: flex;
  flex-direction: column;
  gap: 16px;
  padding: 18px 20px;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: var(--bg-card);
  box-shadow: var(--shadow);
}

.hero-benefits {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.hero-benefits li {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.88rem;
  color: var(--text-soft);
  line-height: 1.35;
}

.hero-benefits li span {
  font-family: var(--serif);
  font-size: 1.05rem;
  color: var(--text);
  width: 1.4em;
  text-align: center;
  flex-shrink: 0;
}

.path-strip {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 10px;
  padding: 12px 14px;
  border-radius: 14px;
  border: 1px solid var(--line);
  background: var(--bg-tint, var(--bg-card));
}

.path-label {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-faint);
  margin-right: 4px;
}

.path-strip a {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text);
  text-decoration: none;
  padding: 6px 12px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--bg-card);
  transition: border-color 0.15s, background 0.15s;
}

.path-strip a:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: 12px;
  letter-spacing: 0.02em;
}

.dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.hero h1 {
  font-family: var(--serif);
  font-size: clamp(2.1rem, 4.5vw, 2.9rem);
  font-weight: 400;
  line-height: 1.12;
  letter-spacing: -0.02em;
  margin-bottom: 12px;
}

.hero-sub {
  font-size: 1rem;
  color: var(--text-soft);
  max-width: 420px;
  margin-bottom: 20px;
  line-height: 1.55;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 13px 22px;
  font-size: 0.925rem;
  font-weight: 600;
  font-family: inherit;
  border-radius: 12px;
  border: none;
  cursor: pointer;
  transition: transform 0.12s, background 0.15s, box-shadow 0.15s;
}

.btn-primary {
  background: var(--accent);
  color: #fff;
}

[data-theme="dark"] .btn-primary {
  color: #0c0b0a;
}

.btn-primary:hover {
  background: var(--accent-deep);
  transform: translateY(-1px);
  box-shadow: 0 6px 20px color-mix(in srgb, var(--accent) 35%, transparent);
}

.btn-ghost {
  background: transparent;
  color: var(--text);
  border: 1px solid var(--line);
}

.btn-ghost:hover {
  background: var(--bg-card);
  border-color: var(--text-faint);
}

.hero-metrics {
  display: flex;
  align-items: center;
  gap: 18px;
  flex-wrap: wrap;
}

.metric {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.metric-value {
  font-family: var(--serif);
  font-size: 1.85rem;
  letter-spacing: -0.02em;
}

.metric-label {
  font-size: 0.8rem;
  color: var(--text-faint);
  font-weight: 500;
}

.metric-divider {
  width: 1px;
  height: 36px;
  background: var(--line);
}

/* ========== Pulse bar ========== */
.pulse-bar {
  position: relative;
  z-index: 1;
  background: var(--accent-soft);
  border-top: 1px solid color-mix(in srgb, var(--accent) 20%, transparent);
  border-bottom: 1px solid color-mix(in srgb, var(--accent) 20%, transparent);
  padding: 13px 0;
}

.pulse-inner {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 0.875rem;
  color: var(--text-soft);
}

.pulse-badge {
  font-size: 0.65rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  padding: 3px 8px;
  background: var(--accent);
  color: #fff;
  border-radius: 6px;
}

[data-theme="dark"] .pulse-badge {
  color: #0c0b0a;
}

/* ========== Sections ========== */
.section {
  position: relative;
  z-index: 1;
  padding: 44px 0;
}

.section-tint {
  background: var(--bg-tint);
}

.section-head {
  display: flex;
  gap: 16px;
  align-items: flex-start;
  margin-bottom: 22px;
}

.section-tag {
  font-family: var(--serif);
  font-size: 1.4rem;
  color: var(--text-faint);
  line-height: 1;
  padding-top: 4px;
}

.section-head h2 {
  font-family: var(--serif);
  font-size: 1.85rem;
  font-weight: 400;
  letter-spacing: -0.02em;
  margin-bottom: 6px;
}

.section-head p {
  color: var(--text-soft);
  font-size: 1rem;
}

/* ========== Pill tabs ========== */
.pill-tabs {
  display: flex;
  gap: 6px;
  margin-bottom: 18px;
  flex-wrap: wrap;
}

.pill {
  padding: 9px 16px;
  font-size: 0.85rem;
  font-weight: 600;
  font-family: inherit;
  background: transparent;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--text-soft);
  cursor: pointer;
  transition: all 0.15s;
}

.pill:hover {
  color: var(--text);
  border-color: var(--text-faint);
}

.pill.active {
  background: var(--text);
  border-color: var(--text);
  color: var(--bg);
}

/* ========== Cards ========== */
.module-panel { display: none; }
.module-panel.active {
  display: block;
  animation: rise 0.3s ease;
}

@keyframes rise {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
  gap: 14px;
}

.card {
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 22px 20px;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  gap: 6px;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
  text-decoration: none;
  color: inherit;
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lift);
  border-color: color-mix(in srgb, var(--accent) 45%, var(--line));
}

.card:hover .card-glyph {
  background: var(--accent);
  color: #fff;
}

[data-theme="dark"] .card:hover .card-glyph {
  color: #0c0b0a;
}

.card-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  margin-bottom: 2px;
}

.live-badge {
  font-size: 0.65rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 3px 8px;
  border-radius: 6px;
  background: var(--accent);
  color: #fff;
}

[data-theme="dark"] .live-badge {
  color: #0c0b0a;
}

.card-glyph {
  width: 42px;
  height: 42px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--accent-soft);
  color: var(--accent);
  border-radius: 12px;
  margin-bottom: 8px;
}

.card-glyph svg {
  width: 22px;
  height: 22px;
}

.card h3 {
  font-size: 1.02rem;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.card p {
  font-size: 0.85rem;
  color: var(--text-soft);
  flex: 1;
  line-height: 1.45;
}

.card-count {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--accent);
  margin-top: 6px;
  letter-spacing: 0.01em;
}

.card-gold {
  border-color: color-mix(in srgb, var(--gold) 35%, var(--line));
  background: linear-gradient(145deg, var(--bg-card), var(--gold-soft));
}

.card-gold .card-glyph {
  background: var(--gold-soft);
  color: var(--gold);
}

.card-gold .card-count {
  color: var(--gold);
}

/* ========== Placeholder ========== */
.placeholder {
  padding: 56px 24px;
  text-align: center;
  color: var(--text-faint);
  background: var(--bg-card);
  border: 1px dashed var(--line);
  border-radius: var(--radius);
}

.placeholder-icon {
  font-family: "Instrument Serif", Georgia, serif;
  font-size: 2rem;
  color: var(--text-faint);
  margin-bottom: 8px;
}

/* ========== Papers ========== */
.paper-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 14px;
}

a.paper {
  text-decoration: none;
  color: inherit;
}

.paper {
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 28px 24px;
  box-shadow: var(--shadow);
  transition: transform 0.18s, box-shadow 0.18s;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.paper:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lift);
}

.paper-num {
  font-family: var(--serif);
  font-size: 1.3rem;
  color: var(--text-faint);
}

.paper h3 {
  font-size: 1.1rem;
  font-weight: 600;
}

.paper p {
  font-size: 0.875rem;
  color: var(--text-soft);
}

.paper-accent {
  border-color: color-mix(in srgb, var(--gold) 40%, var(--line));
  background: linear-gradient(150deg, var(--bg-card), var(--gold-soft));
}

.paper-accent .paper-num {
  color: var(--gold);
}


/* ========== Books ========== */
.book-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
}

.book-card {
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: transform 0.18s, box-shadow 0.18s;
}

.book-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lift);
}

.book-cover {
  height: 120px;
  background: linear-gradient(145deg, color-mix(in srgb, var(--accent) 25%, var(--bg-card)), var(--bg-card));
  display: flex;
  align-items: center;
  justify-content: center;
  border-bottom: 1px solid var(--line);
}

.book-cover-alt {
  background: linear-gradient(145deg, color-mix(in srgb, #6366f1 30%, var(--bg-card)), var(--bg-card));
}

.book-cover-gold {
  background: linear-gradient(145deg, color-mix(in srgb, var(--gold) 35%, var(--bg-card)), var(--bg-card));
}

.book-cover-mark {
  font-family: var(--serif);
  font-size: 2.4rem;
  color: var(--text-faint);
  opacity: 0.85;
}

.book-body {
  padding: 20px 22px 24px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  flex: 1;
}

.book-body h3 {
  font-size: 1.15rem;
  font-weight: 600;
  margin: 0;
}

.book-meta {
  font-size: 0.8rem;
  color: var(--text-faint);
  margin: 0;
}

.book-desc {
  font-size: 0.9rem;
  color: var(--text-soft);
  margin: 0 0 8px;
  flex: 1;
}

.book-buy {
  display: inline-flex;
  align-self: flex-start;
  margin-top: auto;
  text-decoration: none;
}

.books-note {
  margin-top: 24px;
  font-size: 0.85rem;
  color: var(--text-faint);
  max-width: 640px;
}

.books-note code {
  font-size: 0.8em;
  padding: 1px 5px;
  border-radius: 4px;
  background: var(--bg-muted, color-mix(in srgb, var(--line) 40%, transparent));
}

/* ========== Footer ========== */
.footer {
  position: relative;
  z-index: 1;
  border-top: 1px solid var(--line);
  padding: 28px 0;
}

.footer-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
}

.footer-brand {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 600;
  font-size: 0.95rem;
}

.footer-brand .logo-mark {
  width: 26px;
  height: 26px;
  border-radius: 7px;
}

.footer-brand .logo-mark svg {
  width: 14px;
  height: 14px;
}

.footer-note {
  font-size: 0.8rem;
  color: var(--text-faint);
}

.visit-count {
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}


.footer-links {
  display: flex;
  gap: 18px;
}

.footer-links a {
  font-size: 0.8rem;
  color: var(--text-soft);
}

.footer-links a:hover {
  color: var(--text);
}

.footer-disclaimer {
  margin: 18px 0 0;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  font-size: 0.72rem;
  line-height: 1.55;
  color: var(--text-faint);
  max-width: 720px;
}

.footer-disclaimer strong {
  color: var(--text-soft);
  font-weight: 600;
}

/* ========== Responsive ========== */
@media (max-width: 960px) {
  .nav-link {
    padding: 6px 8px;
    font-size: 0.78rem;
  }
}

@media (max-width: 800px) {
  .hero-row {
    grid-template-columns: 1fr;
    gap: 18px;
  }

  .hero-actions {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
  }

  .hero-actions .btn {
    justify-content: center;
    text-align: center;
  }
}

@media (max-width: 900px) {
  .nav-toggle {
    display: flex;
  }

  .header-inner {
    position: relative;
  }

  .header-actions .nav {
    display: none;
    position: absolute;
    top: calc(100% + 8px);
    right: 0;
    left: auto;
    width: min(320px, calc(100vw - 24px));
    flex-direction: column;
    align-items: stretch;
    gap: 2px;
    padding: 12px;
    background: var(--bg-card);
    border: 1px solid var(--line);
    border-radius: 14px;
    box-shadow: var(--shadow-lift);
    z-index: 60;
  }

  .header-actions .nav.is-open {
    display: flex;
  }

  .header-actions .nav .nav-link {
    display: block;
    padding: 12px 14px;
    font-size: 1rem;
    border-radius: 10px;
  }

  .path-strip {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    flex-wrap: nowrap;
    scrollbar-width: none;
  }

  .path-strip::-webkit-scrollbar {
    display: none;
  }

  .path-strip a {
    flex-shrink: 0;
  }
}

@media (max-width: 640px) {
  .hero { padding: 28px 0 20px; }
  .section { padding: 36px 0; }
  .section-head { flex-direction: column; gap: 8px; }
  .card-grid, .paper-grid, .book-grid { grid-template-columns: 1fr; }
  .metric-divider { display: none; }
  .hero-metrics { gap: 16px; }
  .path-strip { gap: 6px; }
  .path-label { width: 100%; margin-bottom: 2px; }
  .pill-tabs {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    flex-wrap: nowrap;
    scrollbar-width: none;
    padding-bottom: 4px;
  }
  .pill-tabs::-webkit-scrollbar { display: none; }
  .pill { flex-shrink: 0; }
}

.why-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 42px;
  height: 42px;
  border-radius: 12px;
  background: var(--line);
  font-family: "Instrument Serif", Georgia, "Times New Roman", serif;
  font-size: 1.35rem;
  line-height: 1;
  color: var(--text);
}