/* 喻晓数学 · 数学几何风格
 * "ink & geometry" — 暖白纸，深靛蓝 + 暖琥珀 + 青绿
 * axes: graph-paper / geometric-illustration / multi-accent
 */

:root {
  --font-display: "Playfair Display", "Noto Serif SC", "Songti SC", serif;
  --font-body: "Source Serif 4", "Noto Serif SC", "Songti SC", serif;
  --font-mono: "JetBrains Mono", monospace;

  /* base */
  --color-paper: oklch(98% 0.005 95);
  --color-paper-2: oklch(95% 0.008 95);
  --color-paper-3: oklch(91% 0.012 95);
  --color-ink: oklch(16% 0.01 260);
  --color-ink-2: oklch(40% 0.02 260);
  --color-ink-3: oklch(58% 0.015 260);

  /* accents */
  --color-blue: oklch(48% 0.19 265);
  --color-blue-soft: oklch(58% 0.15 265);
  --color-blue-dim: oklch(80% 0.10 260);
  --color-amber: oklch(60% 0.19 75);
  --color-amber-soft: oklch(70% 0.16 75);
  --color-amber-dim: oklch(82% 0.12 75);
  --color-teal: oklch(50% 0.17 190);
  --color-teal-dim: oklch(80% 0.10 190);
  --color-rose: oklch(50% 0.19 10);
  --color-rose-dim: oklch(80% 0.12 10);

  /* grade tints */
  --grade-p1: oklch(96% 0.06 265);
  --grade-p2: oklch(96% 0.06 190);
  --grade-p3: oklch(96% 0.06 140);
  --grade-p4: oklch(96% 0.06 75);
  --grade-p5: oklch(96% 0.06 25);
  --grade-p6: oklch(96% 0.06 320);

  --color-accent: var(--color-blue);
  --color-accent-soft: var(--color-blue-soft);
  --color-accent-dim: var(--color-blue-dim);
  --color-focus: oklch(52% 0.18 265);
  --color-divider: oklch(84% 0.015 260);
  --color-divider-strong: oklch(72% 0.03 260);
  --color-success: oklch(50% 0.17 160);
  --color-error: oklch(48% 0.20 25);

  --text-3xs: clamp(0.625rem, 0.6vw + 0.5rem, 0.7rem);
  --text-2xs: clamp(0.7rem, 0.65vw + 0.5rem, 0.82rem);
  --text-xs: clamp(0.78rem, 0.7vw + 0.5rem, 0.92rem);
  --text-sm: clamp(0.9rem, 0.75vw + 0.5rem, 1.05rem);
  --text-base: clamp(1rem, 0.85vw + 0.5rem, 1.2rem);
  --text-md: clamp(1.15rem, 0.95vw + 0.5rem, 1.4rem);
  --text-lg: clamp(1.35rem, 1.1vw + 0.5rem, 1.7rem);
  --text-xl: clamp(1.6rem, 1.3vw + 0.5rem, 2.1rem);
  --text-2xl: clamp(1.9rem, 1.6vw + 0.5rem, 2.6rem);
  --text-3xl: clamp(2.3rem, 2vw + 0.5rem, 3.3rem);
  --text-4xl: clamp(2.8rem, 2.5vw + 0.5rem, 4.2rem);
  --text-display-s: clamp(3.4rem, 3.2vw + 0.5rem, 5.5rem);
  --text-display: clamp(4.2rem, 4.5vw + 0.5rem, 7.5rem);

  --space-2xs: 0.25rem; --space-xs: 0.5rem; --space-sm: 0.75rem;
  --space-md: 1rem; --space-lg: 1.5rem; --space-xl: 2rem;
  --space-2xl: 3rem; --space-3xl: 4rem; --space-4xl: 6rem;
  --space-5xl: 9rem; --space-6xl: 14rem;

  --radius-xs: 2px; --radius-sm: 4px; --radius-md: 8px; --radius-lg: 16px;
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --dur-fast: 150ms; --dur-normal: 300ms; --dur-slow: 500ms;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { overflow-x: clip; -webkit-font-smoothing: antialiased; background: var(--color-paper); }
body {
  font-family: var(--font-body);
  font-size: var(--text-base); line-height: 1.75;
  color: var(--color-ink); background: var(--color-paper);
  overflow-x: clip;
}

strong { font-weight: 600; color: var(--color-ink); }
h1, h2, h3, h4 { font-style: normal; }
.display {
  font-family: var(--font-display);
  font-size: var(--text-display); line-height: 1.08; font-weight: 500;
  letter-spacing: -0.02em; color: var(--color-ink);
}
.display em {
  font-family: inherit; font-style: italic; font-weight: 700;
  background: linear-gradient(135deg, var(--color-blue), var(--color-teal));
  -webkit-background-clip: text; -webkit-text-fill-color: transparent;
  background-clip: text;
}
h2 { font-family: var(--font-display); font-size: var(--text-3xl); line-height: 1.18; color: var(--color-ink); letter-spacing: -0.01em; font-weight: 600; }
h3 { font-family: var(--font-display); font-size: var(--text-xl); line-height: 1.25; color: var(--color-ink); font-weight: 500; }

/* Nav — glass */
.nav {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  padding: var(--space-lg) var(--space-xl);
  background: oklch(98% 0.005 95 / 0.9);
  backdrop-filter: blur(16px); -webkit-backdrop-filter: blur(16px);
  border-bottom: 0.5px solid var(--color-divider);
}
.nav-inner { max-width: 1440px; margin: 0 auto; display: flex; flex-direction: column; align-items: center; gap: var(--space-sm); }
.nav-brand { font-family: var(--font-display); font-size: var(--text-xl); font-weight: 700; color: var(--color-ink); text-decoration: none; letter-spacing: 0.06em; }
.nav-links { display: flex; gap: var(--space-2xl); align-items: center; list-style: none; }
.nav-links a { font-size: var(--text-sm); color: var(--color-ink-2); text-decoration: none; transition: color var(--dur-fast) var(--ease-out); }
.nav-links a:hover { color: var(--color-blue); }
.nav-cta {
  display: inline-block; padding: var(--space-2xs) var(--space-md);
  font-size: var(--text-xs); border: 1px solid var(--color-blue-dim); border-radius: var(--radius-sm);
  color: var(--color-blue); text-decoration: none;
  transition: background var(--dur-fast) var(--ease-out), color var(--dur-fast) var(--ease-out);
}
.nav-cta:hover { background: var(--color-blue); color: #fff; }
@media (max-width: 768px) { .nav-links { gap: var(--space-lg); } .nav-brand { font-size: var(--text-lg); } }

/* Hero — with geometric background */
.hero {
  min-height: 100vh; display: flex; align-items: center; justify-content: center;
  padding: var(--space-xl); text-align: center;
  background: var(--color-paper);
  position: relative; overflow: hidden;
}
.hero-inner { max-width: 900px; position: relative; z-index: 2; }
.hero .display { margin-bottom: var(--space-2xl); }
.hero-sub {
  font-size: var(--text-md); line-height: 1.7; color: var(--color-ink-2);
  max-width: 520px; margin: 0 auto var(--space-2xl);
}
.hero-actions { display: flex; gap: var(--space-md); justify-content: center; flex-wrap: wrap; }

/* Hero geometric illustration */
.hero-geo { position: absolute; inset: 0; z-index: 0; pointer-events: none; }
.hero-geo svg { width: 100%; height: 100%; }

.btn-primary {
  display: inline-block; padding: var(--space-sm) var(--space-2xl);
  font-family: var(--font-body); font-size: var(--text-sm); font-weight: 600;
  background: var(--color-blue); color: #fff;
  border-radius: var(--radius-sm); text-decoration: none; border: none; cursor: pointer;
  transition: filter var(--dur-fast) var(--ease-out);
}
.btn-primary:hover { filter: brightness(1.2); }
.btn-primary:focus-visible { outline: 2px solid var(--color-focus); outline-offset: 2px; }

.btn-ghost {
  display: inline-block; padding: var(--space-sm) var(--space-2xl);
  font-family: var(--font-body); font-size: var(--text-sm);
  background: transparent; color: var(--color-ink);
  border: 0.5px solid var(--color-divider-strong); border-radius: var(--radius-sm);
  text-decoration: none; cursor: pointer;
  transition: border-color var(--dur-fast) var(--ease-out), color var(--dur-fast) var(--ease-out);
}
.btn-ghost:hover { border-color: var(--color-blue); color: var(--color-blue); }
.btn-ghost:focus-visible { outline: 2px solid var(--color-focus); outline-offset: 2px; }

/* Sections */
.wide { max-width: 1280px; margin: 0 auto; padding: 0 var(--space-xl); }
.narrow { max-width: 680px; margin: 0 auto; padding: 0 var(--space-xl); }
.section-tight { padding: var(--space-5xl) var(--space-xl); }
.section-label {
  font-family: var(--font-mono); font-size: var(--text-3xs); font-weight: 600;
  text-transform: uppercase; letter-spacing: 0.16em;
  color: var(--color-blue); margin-bottom: var(--space-md);
}
.section-head { margin-bottom: var(--space-4xl); }
.section-head h2 { margin-bottom: var(--space-sm); }
.section-head p { font-size: var(--text-md); color: var(--color-ink-2); max-width: 520px; }

/* Grade Cards — each with distinct tint */
.grades-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: var(--space-lg); }
.grade-card {
  padding: var(--space-2xl) var(--space-xl);
  border: 0.5px solid var(--color-divider); border-radius: var(--radius-sm);
  transition: border-color var(--dur-fast) var(--ease-out), box-shadow var(--dur-fast) var(--ease-out);
  position: relative; overflow: hidden;
}
.grade-card::before {
  content: ""; position: absolute; left: 0; top: 0; bottom: 0; width: 3px;
  transition: width var(--dur-normal) var(--ease-out);
}
.grade-card:nth-child(1) { background: var(--grade-p1); }
.grade-card:nth-child(1)::before { background: var(--color-blue); }
.grade-card:nth-child(2) { background: var(--grade-p2); }
.grade-card:nth-child(2)::before { background: var(--color-teal); }
.grade-card:nth-child(3) { background: var(--grade-p3); }
.grade-card:nth-child(3)::before { background: oklch(52% 0.17 140); }
.grade-card:nth-child(4) { background: var(--grade-p4); }
.grade-card:nth-child(4)::before { background: var(--color-amber); }
.grade-card:nth-child(5) { background: var(--grade-p5); }
.grade-card:nth-child(5)::before { background: var(--color-rose); }
.grade-card:nth-child(6) { background: var(--grade-p6); }
.grade-card:nth-child(6)::before { background: oklch(50% 0.17 320); }
.grade-card:hover { border-color: var(--color-divider-strong); box-shadow: 0 2px 12px oklch(0% 0 0 / 0.04); }
.grade-card:hover::before { width: 5px; }
.grade-num { font-family: var(--font-display); font-size: var(--text-4xl); line-height: 1; font-weight: 700; margin-bottom: var(--space-xs); }
.grade-card:nth-child(1) .grade-num { color: var(--color-blue); }
.grade-card:nth-child(2) .grade-num { color: var(--color-teal); }
.grade-card:nth-child(3) .grade-num { color: oklch(52% 0.17 140); }
.grade-card:nth-child(4) .grade-num { color: var(--color-amber); }
.grade-card:nth-child(5) .grade-num { color: var(--color-rose); }
.grade-card:nth-child(6) .grade-num { color: oklch(50% 0.17 320); }
.grade-name { font-family: var(--font-display); font-size: var(--text-lg); font-weight: 600; color: var(--color-ink); margin-bottom: var(--space-md); }
.grade-list { list-style: none; padding: 0; margin: 0; }
.grade-list li { font-size: var(--text-sm); color: var(--color-ink-2); line-height: 2; padding-left: var(--space-md); position: relative; }
.grade-list li::before { content: "·"; position: absolute; left: 0; color: var(--color-ink-3); }
@media (max-width: 768px) { .grades-grid { grid-template-columns: 1fr; } }

/* Stats — with colored background strip */
.stats-strip { background: linear-gradient(135deg, var(--grade-p1), var(--grade-p2), var(--grade-p4)); padding: var(--space-4xl) 0; }
.stats-row { display: grid; grid-template-columns: repeat(4, 1fr); gap: var(--space-2xl); text-align: center; }
.stat-num { font-family: var(--font-display); font-size: var(--text-4xl); line-height: 1; font-weight: 700; margin-bottom: var(--space-xs); position: relative; display: inline-block; }
.stat-num::after { content: ""; position: absolute; bottom: -6px; left: 50%; transform: translateX(-50%); width: 24px; height: 2px; border-radius: 1px; }
.stats-row > div:nth-child(1) .stat-num { color: var(--color-blue); }
.stats-row > div:nth-child(1) .stat-num::after { background: var(--color-blue-dim); }
.stats-row > div:nth-child(2) .stat-num { color: var(--color-teal); }
.stats-row > div:nth-child(2) .stat-num::after { background: var(--color-teal-dim); }
.stats-row > div:nth-child(3) .stat-num { color: var(--color-amber); }
.stats-row > div:nth-child(3) .stat-num::after { background: var(--color-amber-dim); }
.stats-row > div:nth-child(4) .stat-num { color: var(--color-rose); }
.stats-row > div:nth-child(4) .stat-num::after { background: var(--color-rose-dim); }
.stat-label { font-size: var(--text-xs); color: var(--color-ink-3); margin-top: var(--space-sm); }
@media (max-width: 768px) { .stats-row { grid-template-columns: repeat(2, 1fr); gap: var(--space-xl); } }

/* Samples — 3-col, clean cards */
.samples-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: var(--space-lg); }
.sample-card {
  display: block; text-decoration: none; color: inherit; cursor: pointer;
  padding: var(--space-xl); background: var(--color-paper-2);
  border: 0.5px solid var(--color-divider); border-radius: var(--radius-sm);
  transition: border-color var(--dur-fast) var(--ease-out), box-shadow var(--dur-fast) var(--ease-out), transform var(--dur-fast) var(--ease-out);
}
.sample-card:hover { border-color: var(--color-blue-dim); box-shadow: 0 2px 16px oklch(0% 0 0 / 0.05); transform: translateY(-2px); }
.sample-badge {
  display: inline-block; padding: var(--space-2xs) var(--space-sm);
  font-family: var(--font-mono); font-size: var(--text-3xs); font-weight: 600;
  text-transform: uppercase; letter-spacing: 0.1em;
  border: 0.5px solid var(--color-blue-dim); color: var(--color-blue);
  background: var(--color-paper-3); border-radius: var(--radius-xs); margin-bottom: var(--space-md);
}
.sample-card:nth-child(2) .sample-badge { color: var(--color-teal); border-color: var(--color-teal-dim); }
.sample-card:nth-child(3) .sample-badge { color: oklch(52% 0.17 140); border-color: oklch(80% 0.08 140); }
.sample-card:nth-child(4) .sample-badge { color: var(--color-amber); border-color: var(--color-amber-dim); }
.sample-card:nth-child(5) .sample-badge { color: var(--color-rose); border-color: var(--color-rose-dim); }
.sample-card:nth-child(6) .sample-badge { color: oklch(50% 0.17 320); border-color: oklch(80% 0.10 320); }
.sample-card h3 { color: var(--color-ink); margin-bottom: var(--space-xs); font-weight: 600; }
.sample-card p { font-size: var(--text-sm); color: var(--color-ink-2); }
.card-arrow { display: block; margin-top: var(--space-sm); font-family: var(--font-mono); font-size: var(--text-3xs); color: var(--color-blue); letter-spacing: 0.06em; opacity: 0; transform: translateX(-4px); transition: opacity var(--dur-fast) var(--ease-out), transform var(--dur-fast) var(--ease-out); }
.sample-card:hover .card-arrow { opacity: 1; transform: translateX(0); }
@media (max-width: 768px) {
  .card-arrow { opacity: 0.7; transform: translateX(0); font-size: 0.6rem; }
}
@media (max-width: 768px) { .samples-grid { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 414px) { .samples-grid { grid-template-columns: 1fr; } }

/* Features — with alternating accent numbers */
.features-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: var(--space-2xl); }
.feature-item { padding: var(--space-lg) 0; border-top: 0.5px solid var(--color-divider); }
.feature-link { display: block; text-decoration: none !important; color: inherit; cursor: pointer; transition: border-color var(--dur-fast) var(--ease-out), background var(--dur-fast) var(--ease-out); padding: var(--space-lg); margin: 0 calc(-1 * var(--space-lg)); border-radius: var(--radius-sm); }
.feature-link:hover, .feature-link h3, .feature-link p, .feature-link .feature-num { text-decoration: none; }
.feature-link:hover { background: var(--color-paper-2); }
.feature-link .card-arrow { display: block; margin-top: var(--space-sm); font-family: var(--font-mono); font-size: var(--text-3xs); color: var(--color-blue); letter-spacing: 0.06em; opacity: 0; transform: translateX(-4px); transition: opacity var(--dur-fast) var(--ease-out), transform var(--dur-fast) var(--ease-out); }
.feature-link:hover .card-arrow { opacity: 1; transform: translateX(0); }
@media (max-width: 768px) {
  .feature-link { padding: var(--space-md); margin: 0 calc(-1 * var(--space-md)); }
  .feature-link .card-arrow { opacity: 0.7; transform: translateX(0); }
}
.feature-num { font-family: var(--font-mono); font-size: var(--text-3xs); font-weight: 700; text-transform: uppercase; letter-spacing: 0.12em; margin-bottom: var(--space-md); }
.feature-item:nth-child(1) .feature-num { color: var(--color-blue); }
.feature-item:nth-child(2) .feature-num { color: var(--color-teal); }
.feature-item:nth-child(3) .feature-num { color: var(--color-amber); }
.feature-item:nth-child(4) .feature-num { color: var(--color-rose); }
.feature-item:nth-child(5) .feature-num { color: oklch(52% 0.17 140); }
.feature-item:nth-child(6) .feature-num { color: oklch(50% 0.17 320); }
.feature-item h3 { margin-bottom: var(--space-sm); font-weight: 600; }
.feature-item p { font-size: var(--text-sm); color: var(--color-ink-2); line-height: 1.7; }
@media (max-width: 768px) { .features-grid { grid-template-columns: 1fr; } }

/* CTA */
.cta-section {
  text-align: center; padding: var(--space-5xl) var(--space-xl);
  background: linear-gradient(135deg, var(--grade-p1), var(--grade-p4), oklch(96% 0.02 320));
  border-radius: var(--radius-sm);
  border: 0.5px solid var(--color-divider);
  position: relative; overflow: hidden;
}
.cta-section::before {
  content: ""; position: absolute; top: 0; left: 50%; transform: translateX(-50%);
  width: 60px; height: 2px;
  background: linear-gradient(to right, var(--color-blue), var(--color-teal));
  border-radius: 1px;
}
.cta-section .display-s { font-family: var(--font-display); font-size: var(--text-display-s); color: var(--color-ink); margin-bottom: var(--space-md); }
.cta-section p { font-size: var(--text-md); color: var(--color-ink-2); max-width: 460px; margin: 0 auto var(--space-2xl); }

/* Footer */
.footer { padding: var(--space-3xl) var(--space-xl); text-align: center; border-top: 0.5px solid var(--color-divider); background: var(--color-paper-2); }
.footer-brand { font-family: var(--font-display); font-size: var(--text-lg); font-weight: 600; color: var(--color-ink); margin-bottom: var(--space-sm); }
.footer p { font-size: var(--text-2xs); color: var(--color-ink-3); }

/* ===== ORNAMENT ===== */

/* Graph paper texture — more visible */
body::before {
  content: ""; position: fixed; inset: 0; z-index: 0; pointer-events: none; opacity: 0.04;
  background-image:
    linear-gradient(var(--color-divider) 1px, transparent 1px),
    linear-gradient(90deg, var(--color-divider) 1px, transparent 1px);
  background-size: 40px 40px;
}
.wide, .narrow, .hero, .nav, .footer, .stats-strip { position: relative; z-index: 1; }

/* Section rule */
.section-rule { max-width: 1280px; margin: 0 auto; padding: 0 var(--space-xl); }
.section-rule-inner { height: 0.5px; background: var(--color-divider); }

/* Ornament */
.ornament {
  display: flex; align-items: center; justify-content: center; gap: var(--space-md);
  height: 32px; border: none; background: none; margin: 0;
}
.ornament::before, .ornament::after {
  content: ""; flex: 1; height: 0.5px;
  background: linear-gradient(to right, transparent, var(--color-divider-strong), transparent);
}
.ornament-dot {
  width: 3px; height: 3px; border-radius: 50%;
  background: var(--color-blue); flex-shrink: 0;
}

/* Motion */
@keyframes fade-up {
  from { opacity: 0; transform: translateY(28px); }
  to { opacity: 1; transform: translateY(0); }
}
.animate-in { animation: fade-up 0.6s var(--ease-out) both; }
.delay-1 { animation-delay: 0.1s; }
.delay-2 { animation-delay: 0.2s; }
.delay-3 { animation-delay: 0.3s; }
@media (prefers-reduced-motion: reduce) { .animate-in { animation: none; opacity: 1; } }

/* ===== MOBILE (≤768px) ===== */
@media (max-width: 768px) {
  :root {
    --text-display: clamp(2.4rem, 8vw + 0.5rem, 3.8rem);
    --text-display-s: clamp(1.8rem, 6vw + 0.5rem, 3rem);
    --text-3xl: clamp(1.6rem, 5vw + 0.5rem, 2.4rem);
  }
  .nav { padding: var(--space-sm) var(--space-md); }
  .nav-inner { gap: var(--space-2xs); }
  .nav-brand { font-size: var(--text-md); letter-spacing: 0.04em; }
  .nav-links { gap: var(--space-md); flex-wrap: wrap; justify-content: center; }
  .nav-links a { font-size: var(--text-2xs); }
  .nav-cta { padding: var(--space-2xs) var(--space-sm); font-size: var(--text-3xs); }

  .hero { min-height: 80vh; padding: var(--space-5xl) var(--space-md) var(--space-2xl); }
  .hero .display { margin-bottom: var(--space-lg); }
  .hero-sub { font-size: var(--text-sm); max-width: 300px; }
  .hero-actions { flex-direction: column; align-items: center; gap: var(--space-sm); }
  .hero-geo { opacity: 0.5; }
  .btn-primary, .btn-ghost { width: 100%; max-width: 280px; text-align: center; padding: var(--space-md) var(--space-xl); font-size: var(--text-base); }

  .section-tight { padding: var(--space-3xl) var(--space-md); }
  .wide, .narrow { padding: 0 var(--space-md); }
  .section-head { margin-bottom: var(--space-2xl); }
  .section-head h2 { font-size: var(--text-2xl); }
  .section-head p { font-size: var(--text-sm); }

  .grades-grid { grid-template-columns: 1fr; gap: var(--space-md); }
  .grade-card { padding: var(--space-lg) var(--space-md); }
  .grade-num { font-size: var(--text-2xl); }
  .grade-name { font-size: var(--text-md); }
  .grade-list li { font-size: var(--text-xs); line-height: 1.8; }

  .samples-grid { grid-template-columns: repeat(2, 1fr); gap: var(--space-sm); }
  .sample-card { padding: var(--space-md); }
  .sample-card h3 { font-size: var(--text-md); }
  .sample-card p { font-size: var(--text-2xs); }

  .features-grid { grid-template-columns: 1fr; gap: var(--space-xl); }
  .feature-item h3 { font-size: var(--text-lg); }

  .stats-strip { padding: var(--space-2xl) 0; }
  .stats-row { grid-template-columns: repeat(2, 1fr); gap: var(--space-lg); }
  .stat-num { font-size: var(--text-2xl); }

  .cta-section { padding: var(--space-3xl) var(--space-md); }
  .cta-section p { font-size: var(--text-sm); }

  .ornament { height: 24px; }
  .footer { padding: var(--space-2xl) var(--space-md); }

  .sample-nav { padding: var(--space-sm) var(--space-md); }
  .sample-nav .title { font-size: var(--text-sm); }
  .sample-container { padding: var(--space-xl) var(--space-md) var(--space-3xl); }
  .sample-header h1 { font-size: var(--text-2xl); }
  .sample-header .meta { gap: var(--space-md); font-size: var(--text-2xs); }
  .concept h2 { font-size: var(--text-lg); }
  .steps li { font-size: var(--text-xs); padding-left: var(--space-xl); }
  .steps li::before { width: 18px; height: 18px; font-size: 0.6rem; }
}

/* ===== SMALL PHONE (≤414px) ===== */
@media (max-width: 414px) {
  :root { --text-display: clamp(2rem, 7vw + 0.5rem, 2.8rem); }
  .hero { min-height: 75vh; padding-top: var(--space-6xl); }
  .samples-grid { grid-template-columns: 1fr; }
  .stats-row { grid-template-columns: 1fr 1fr; gap: var(--space-md); }
}

/* Sample page nav (desktop) */
.sample-nav { position: sticky; top: 0; z-index: 100; padding: var(--space-md) var(--space-xl); background: oklch(98% 0.005 95 / 0.9); backdrop-filter: blur(16px); border-bottom: 0.5px solid var(--color-divider); display: flex; align-items: center; justify-content: space-between; }
.sample-nav a { font-size: var(--text-sm); color: var(--color-ink-2); text-decoration: none; transition: color var(--dur-fast) var(--ease-out); }
.sample-nav a:hover { color: var(--color-blue); }
.sample-nav .back { font-family: var(--font-mono); font-size: var(--text-2xs); }
.sample-nav .title { font-family: var(--font-display); font-size: var(--text-md); color: var(--color-ink); }