/* =========================================================
   Variant A — Classic Top Nav (Blue-Purple Accent)
   Swiss Modern · Editorial · Light Neo-Brutalist
   ========================================================= */

:root {
  /* Colors */
  --color-ink: #0a0a0a;
  --color-paper: #ffffff;
  --color-mist: #f4f4f2;
  --color-line: #0a0a0a;
  --color-muted: #5b5b5b;
  --color-accent: #4f46e5;
  --color-accent-deep: #312e81;
  --color-accent-soft: #eef0ff;

  /* Layout */
  --w-max: 920px;
  --w-gutter: 24px;
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 16px;
  --space-4: 24px;
  --space-5: 40px;
  --space-6: 64px;
  --space-7: 96px;
  --space-8: 128px;

  /* Type */
  --font-sans: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", -apple-system, BlinkMacSystemFont, "Helvetica Neue", Arial, sans-serif;
  --font-mono: "JetBrains Mono", "SF Mono", Menlo, Consolas, monospace;

  /* Lines */
  --line-thin: 1px;
  --line-mid: 2px;
  --line-bold: 3px;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-ink);
  background: var(--color-paper);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }

.container {
  max-width: var(--w-max);
  margin: 0 auto;
  padding-left: var(--w-gutter);
  padding-right: var(--w-gutter);
}

/* ===== Skip link ===== */
.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--color-ink);
  color: var(--color-paper);
  padding: 8px 16px;
  z-index: 999;
}
.skip-link:focus { left: 16px; top: 16px; }

/* ===== Header / Nav ===== */
.site-header {
  position: sticky;
  top: 0;
  background: var(--color-paper);
  z-index: 50;
}
.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
  gap: var(--space-4);
}
.nav-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 900;
  font-size: 18px;
  letter-spacing: -0.01em;
}
.nav-brand img {
  width: 28px;
  height: 28px;
  display: block;
}
.nav-list {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav-list a {
  font-size: 14px;
  font-weight: 500;
  padding: 4px 2px;
  border-bottom: 2px solid transparent;
  transition: border-color 0.15s ease;
}
.nav-list a:hover,
.nav-list a:focus-visible { border-bottom-color: var(--color-ink); outline: none; }
.nav-list a[aria-current="page"] { border-bottom-color: var(--color-accent); }

.nav-toggle {
  display: none;
  width: 40px;
  height: 40px;
  background: transparent;
  border: var(--line-mid) solid var(--color-ink);
  cursor: pointer;
  padding: 0;
  position: relative;
}
.nav-toggle span,
.nav-toggle span::before,
.nav-toggle span::after {
  content: "";
  position: absolute;
  left: 8px;
  width: 20px;
  height: 2px;
  background: var(--color-ink);
}
.nav-toggle span { top: 50%; transform: translateY(-50%); }
.nav-toggle span::before { top: -7px; left: 0; }
.nav-toggle span::after { top: 7px; left: 0; }

.site-header::after {
  content: "";
  display: block;
  height: var(--line-bold);
  background: var(--color-line);
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 48px;
  padding: 0 24px;
  font-size: 15px;
  font-weight: 700;
  font-family: inherit;
  border: var(--line-mid) solid var(--color-ink);
  border-radius: 0;
  cursor: pointer;
  letter-spacing: 0.01em;
  transition: background 0.15s ease, color 0.15s ease, border-color 0.15s ease;
  text-align: center;
  line-height: 1;
}
.btn-primary {
  background: var(--color-accent);
  color: var(--color-paper);
  border-color: var(--color-accent);
}
.btn-primary:hover,
.btn-primary:focus-visible {
  background: var(--color-ink);
  border-color: var(--color-ink);
  color: var(--color-paper);
  outline: none;
}
.btn-secondary {
  background: var(--color-paper);
  color: var(--color-ink);
  border-color: var(--color-ink);
}
.btn-secondary:hover,
.btn-secondary:focus-visible {
  background: var(--color-ink);
  color: var(--color-paper);
  outline: none;
}
.btn-small {
  height: 36px;
  padding: 0 16px;
  font-size: 13px;
}

:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 2px;
}

/* ===== Hero ===== */
.hero {
  padding: var(--space-7) 0 var(--space-6);
}
.eyebrow {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-muted);
  margin: 0 0 var(--space-4);
  display: inline-block;
  border-bottom: var(--line-mid) solid var(--color-ink);
  padding-bottom: 6px;
}
.hero-title {
  font-size: clamp(40px, 7.5vw, 84px);
  line-height: 0.95;
  font-weight: 900;
  letter-spacing: -0.03em;
  margin: 0 0 var(--space-4);
}
.hero-title .accent { color: var(--color-accent); }
.hero-lede {
  font-size: clamp(15px, 1.4vw, 17px);
  line-height: 1.7;
  max-width: 56ch;
  color: var(--color-ink);
  margin: 0 0 var(--space-5);
}
.hero-cta {
  display: flex;
  gap: var(--space-3);
  flex-wrap: wrap;
}

/* ===== Section base ===== */
.section {
  padding: var(--space-6) 0;
  border-top: var(--line-bold) solid var(--color-line);
}
.section-head {
  margin-bottom: var(--space-5);
}
.section-eyebrow {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-muted);
  margin: 0 0 var(--space-2);
}
.section-title {
  font-size: clamp(28px, 4vw, 44px);
  line-height: 1.05;
  font-weight: 900;
  letter-spacing: -0.02em;
  margin: 0;
}
.section-title .accent { color: var(--color-accent); }

/* ===== Value bar (3 columns, full accent) ===== */
.value-bar {
  background: var(--color-accent);
  color: var(--color-paper);
  padding: var(--space-5) 0;
  border-top: var(--line-bold) solid var(--color-ink);
  border-bottom: var(--line-bold) solid var(--color-ink);
}
.value-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-5);
}
.value-item h3 {
  font-size: 20px;
  font-weight: 900;
  margin: 0 0 6px;
  letter-spacing: -0.01em;
}
.value-item p {
  margin: 0;
  font-size: 14px;
  line-height: 1.6;
  opacity: 0.95;
}

/* ===== Definition list (features) ===== */
.cap-list {
  list-style: none;
  margin: 0;
  padding: 0;
}
.cap-list li {
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: var(--space-4);
  padding: var(--space-4) 0;
  border-top: var(--line-mid) solid var(--color-ink);
  align-items: baseline;
}
.cap-list li:last-child { border-bottom: var(--line-mid) solid var(--color-ink); }
.cap-list .cap-title {
  font-size: 20px;
  font-weight: 900;
  letter-spacing: -0.01em;
  margin: 0;
}
.cap-list .cap-desc {
  font-size: 15px;
  line-height: 1.6;
  color: var(--color-ink);
  margin: 0;
}

/* ===== Numbered scenes ===== */
.scene-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-4);
}
.scene-item {
  padding: var(--space-4);
  border: var(--line-mid) solid var(--color-ink);
  background: var(--color-paper);
}
.scene-num {
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 700;
  color: var(--color-accent);
  margin: 0 0 var(--space-2);
  letter-spacing: 0.08em;
}
.scene-title {
  font-size: 22px;
  font-weight: 900;
  margin: 0 0 8px;
  letter-spacing: -0.01em;
}
.scene-desc {
  font-size: 14px;
  line-height: 1.6;
  margin: 0;
  color: var(--color-muted);
}

/* ===== Platforms ===== */
.platform-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: var(--space-2);
  border-top: var(--line-mid) solid var(--color-ink);
  border-bottom: var(--line-mid) solid var(--color-ink);
}
.platform-grid.cols-6 {
  grid-template-columns: repeat(6, 1fr);
}
.platform-grid > div {
  padding: var(--space-3) 0;
  border-right: var(--line-thin) solid var(--color-ink);
  text-align: center;
  font-weight: 700;
  font-size: 14px;
}
.platform-grid > div:last-child { border-right: none; }

/* ===== Download CTA ===== */
.cta-dark {
  background: var(--color-ink);
  color: var(--color-paper);
  padding: var(--space-6) 0;
  border-top: var(--line-bold) solid var(--color-ink);
}
.cta-dark h2 {
  font-size: clamp(28px, 4vw, 44px);
  font-weight: 900;
  line-height: 1.05;
  letter-spacing: -0.02em;
  margin: 0 0 var(--space-4);
}
.cta-dark h2 .accent { color: var(--color-accent); }
.cta-dark .btn-primary {
  background: var(--color-accent);
  border-color: var(--color-accent);
  color: var(--color-paper);
}
.cta-dark .btn-primary:hover,
.cta-dark .btn-primary:focus-visible {
  background: var(--color-paper);
  color: var(--color-ink);
  border-color: var(--color-paper);
}

/* ===== Download page cards ===== */
.dl-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-4);
}
.dl-card {
  border: var(--line-mid) solid var(--color-ink);
  padding: var(--space-4);
  background: var(--color-paper);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}
.dl-card h3 {
  font-size: 22px;
  font-weight: 900;
  margin: 0;
  letter-spacing: -0.01em;
}
.dl-meta {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--color-muted);
  letter-spacing: 0.05em;
}
.dl-card .btn { margin-top: auto; }

/* ===== FAQ ===== */
.faq-item {
  border-top: var(--line-mid) solid var(--color-ink);
  padding: var(--space-4) 0;
}
.faq-item:last-child { border-bottom: var(--line-mid) solid var(--color-ink); }
.faq-q {
  font-size: 18px;
  font-weight: 700;
  margin: 0 0 var(--space-2);
}
.faq-a {
  font-size: 15px;
  line-height: 1.7;
  color: var(--color-ink);
  margin: 0;
}

/* ===== Breadcrumb ===== */
.breadcrumb {
  display: flex;
  gap: 8px;
  font-size: 13px;
  color: var(--color-muted);
  padding: var(--space-3) 0;
  border-bottom: var(--line-thin) solid var(--color-ink);
  margin-bottom: var(--space-5);
  flex-wrap: wrap;
}
.breadcrumb a:hover { text-decoration: underline; }

/* ===== Footer ===== */
.site-footer {
  background: var(--color-mist);
  border-top: var(--line-bold) solid var(--color-ink);
  padding: var(--space-6) 0 var(--space-4);
}
.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: var(--space-4);
  margin-bottom: var(--space-5);
}
.footer-grid h4 {
  font-size: 14px;
  font-weight: 900;
  margin: 0 0 var(--space-3);
  letter-spacing: 0.02em;
  text-transform: uppercase;
}
.footer-grid ul {
  list-style: none;
  padding: 0;
  margin: 0;
}
.footer-grid li { margin: 0 0 8px; }
.footer-grid a {
  font-size: 14px;
  color: var(--color-ink);
}
.footer-grid a:hover { color: var(--color-accent); text-decoration: underline; }
.footer-brand p {
  font-size: 14px;
  line-height: 1.6;
  margin: var(--space-2) 0 0;
  color: var(--color-muted);
  max-width: 36ch;
}
.footer-bottom {
  border-top: var(--line-mid) solid var(--color-ink);
  padding-top: var(--space-3);
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-2);
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--color-muted);
  letter-spacing: 0.04em;
}

/* ===== Guide page specifics ===== */
.guide-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-4);
}
.guide-card {
  border: var(--line-mid) solid var(--color-ink);
  padding: var(--space-4);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}
.guide-card h3 {
  font-size: 20px;
  font-weight: 900;
  margin: 0;
  letter-spacing: -0.01em;
}
.guide-card .step {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--color-accent);
  letter-spacing: 0.08em;
  font-weight: 700;
}
.guide-card ol {
  padding-left: 20px;
  margin: 0;
  font-size: 14px;
  line-height: 1.7;
}
.guide-card ol li { margin-bottom: 4px; }

/* ===== Product page specifics ===== */
.product-hero {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-5);
  align-items: center;
}
.product-hero img {
  border: var(--line-mid) solid var(--color-ink);
  width: 100%;
  height: auto;
}

/* ===== Responsive ===== */
@media (max-width: 820px) {
  .nav-list {
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--color-paper);
    flex-direction: column;
    align-items: flex-start;
    padding: var(--space-3) var(--w-gutter) var(--space-4);
    gap: var(--space-3);
    border-bottom: var(--line-bold) solid var(--color-ink);
    display: none;
  }
  .nav-list.show { display: flex; }
  .nav-list .btn { width: 100%; }
  .nav-toggle { display: block; }
  .nav-list a { font-size: 16px; }

  .value-grid { grid-template-columns: 1fr; gap: var(--space-4); }
  .cap-list li { grid-template-columns: 1fr; gap: var(--space-2); }
  .scene-list { grid-template-columns: 1fr; }
  .platform-grid { grid-template-columns: repeat(2, 1fr); }
  .platform-grid > div { border-right: none; }
  .platform-grid > div:nth-child(odd) { border-right: var(--line-thin) solid var(--color-ink); }
  .dl-grid { grid-template-columns: 1fr; }
  .guide-grid { grid-template-columns: 1fr; }
  .product-hero { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr 1fr; }

  .hero { padding: var(--space-5) 0 var(--space-5); }
  .section { padding: var(--space-5) 0; }
}

@media (max-width: 480px) {
  .footer-grid { grid-template-columns: 1fr; }
  .hero-cta .btn { width: 100%; }
}