:root {
  --bg: #f2f5f8;
  --surface: #ffffff;
  --surface-alt: #e9f3fa;
  --text: #172431;
  --muted: #5d6b78;
  --line: #d7e0e8;
  --accent: #0d6b9f;
  --accent-dark: #084d74;
  --warning: #fff7df;
  --warning-line: #e7bd45;
  --radius: 20px;
  --shadow: 0 14px 40px rgba(24, 48, 70, .08);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--text);
  background: var(--bg);
  font-family: Inter, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Arial, sans-serif;
  font-size: 18px;
  line-height: 1.68;
}
a { color: var(--accent); text-underline-offset: 3px; }
a:hover { color: var(--accent-dark); }
img { max-width: 100%; height: auto; }

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  border-bottom: 1px solid rgba(215, 224, 232, .9);
  background: rgba(255, 255, 255, .94);
  backdrop-filter: blur(14px);
}
.header-inner, .container { width: min(1160px, calc(100% - 32px)); margin-inline: auto; }
.header-inner { display: flex; align-items: center; justify-content: space-between; gap: 24px; min-height: 72px; }
.brand { color: var(--text); font-weight: 800; font-size: 22px; text-decoration: none; letter-spacing: -.02em; }
.brand span { color: var(--accent); }
.header-nav { display: flex; align-items: center; gap: 22px; font-size: 15px; font-weight: 700; }
.header-nav a { color: var(--text); text-decoration: none; }
.header-nav a:hover { color: var(--accent); }
.header-actions { display: flex; align-items: center; gap: 18px; }
.quiet-link { color: var(--text); font-size: 15px; font-weight: 700; text-decoration: none; }
.quiet-link:hover { color: var(--accent); }
.language-menu { position: relative; }
.language-menu summary { cursor: pointer; list-style: none; padding: 8px 12px; border: 1px solid var(--line); border-radius: 10px; background: #fff; font-size: 14px; font-weight: 800; }
.language-menu summary::-webkit-details-marker { display: none; }
.language-menu summary::after { content: " ▾"; color: var(--muted); }
.language-panel { position: absolute; right: 0; top: calc(100% + 9px); width: 230px; padding: 14px; border: 1px solid var(--line); border-radius: 12px; background: #fff; box-shadow: var(--shadow); }
.language-panel a, .language-panel span { display: block; padding: 7px 9px; border-radius: 7px; font-size: 14px; text-decoration: none; }
.language-panel a { color: var(--accent); font-weight: 800; background: var(--surface-alt); }
.language-panel span { color: #89939c; }
.language-panel p { margin: 10px 9px 3px; color: var(--muted); font-size: 12px; line-height: 1.4; }

.start-hero { padding: 76px 0 32px; }
.start-hero h1 { max-width: 850px; }
.start-card { display: grid; grid-template-columns: 74px minmax(0, 1fr); gap: 26px; align-items: start; max-width: 920px; margin-top: 44px; padding: clamp(26px, 5vw, 48px); border: 1px solid #bad7e8; border-radius: 24px; background: linear-gradient(145deg, #fff, #eaf6fd); box-shadow: var(--shadow); }
.guide-icon { display: grid; place-items: center; width: 64px; height: 64px; border: 1px solid #b9d7e8; border-radius: 18px; background: #fff; font-size: 32px; box-shadow: 0 8px 18px rgba(24, 48, 70, .08); }
.start-label { margin: 0 0 5px !important; color: var(--accent) !important; font-size: 14px; font-weight: 900; letter-spacing: .07em; text-transform: uppercase; }
.start-copy h2 { margin: 0 0 12px; font-size: clamp(30px, 4vw, 44px); }
.start-copy p { max-width: 690px; margin: 0 0 24px; color: var(--muted); }
.primary-button { display: inline-flex; align-items: center; justify-content: center; min-height: 54px; padding: 13px 22px; border-radius: 12px; color: #fff; background: var(--accent); font-weight: 850; text-decoration: none; box-shadow: 0 10px 22px rgba(13, 107, 159, .18); }
.primary-button:hover { color: #fff; background: var(--accent-dark); }
.top-notice-wrap { padding-top: 28px; }
.top-notice-wrap .notice { max-width: 920px; margin-bottom: 0; }
.article-top-notice { margin: 24px 0 0; }
.learning-path { max-width: 920px; padding: 45px 0 80px; }
.learning-path h2 { margin: 0 0 20px; font-size: clamp(29px, 4vw, 40px); }
.path-list { margin: 0; padding: 0; list-style: none; border-top: 1px solid var(--line); }
.path-list li { display: grid; grid-template-columns: 42px minmax(0, 1fr) auto; gap: 15px; align-items: center; padding: 20px 4px; border-bottom: 1px solid var(--line); }
.path-list li > span { display: grid; place-items: center; width: 34px; height: 34px; border-radius: 10px; background: #e5edf2; color: var(--muted); font-size: 14px; font-weight: 900; }
.path-list strong, .path-list small { display: block; }
.path-list small { margin-top: 2px; color: var(--muted); font-size: 14px; }
.path-list em { color: #8a959e; font-size: 12px; font-style: normal; font-weight: 800; text-transform: uppercase; letter-spacing: .05em; }

.hero { padding: 72px 0 38px; }
.eyebrow { margin: 0 0 12px; color: var(--accent); font-size: 14px; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
h1, h2, h3 { line-height: 1.18; letter-spacing: -.025em; }
h1 { margin: 0; max-width: 980px; font-size: clamp(38px, 6vw, 68px); }
.lead { max-width: 830px; margin: 24px 0 0; color: var(--muted); font-size: clamp(20px, 2.2vw, 25px); line-height: 1.5; }
.meta { display: flex; flex-wrap: wrap; gap: 10px 22px; margin: 24px 0 0; color: var(--muted); font-size: 15px; }

.notice {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 14px;
  margin: 0 0 32px;
  padding: 20px 22px;
  border: 1px solid var(--warning-line);
  border-radius: 16px;
  background: var(--warning);
}
.notice-icon { display: grid; place-items: center; width: 30px; height: 30px; border-radius: 50%; color: #765900; background: #ffe08a; font-size: 18px; font-weight: 900; line-height: 1; }
.notice strong { display: block; margin-bottom: 3px; }
.notice p { margin: 0; }

.card-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; padding: 10px 0 72px; }
.card {
  display: flex;
  flex-direction: column;
  min-height: 280px;
  padding: 28px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: var(--shadow);
}
.card.featured { grid-column: span 2; background: linear-gradient(145deg, #fff, #edf8ff); }
.card h2, .card h3 { margin: 10px 0 12px; font-size: 27px; }
.card p { margin: 0 0 22px; color: var(--muted); }
.card-link { margin-top: auto; font-weight: 800; }
.status { align-self: flex-start; padding: 5px 10px; border-radius: 999px; background: #eaf1f5; color: var(--muted); font-size: 12px; font-weight: 800; text-transform: uppercase; letter-spacing: .04em; }
.status.ready { color: #075b41; background: #dff5ec; }

.article-shell { display: grid; grid-template-columns: 250px minmax(0, 1fr); gap: 30px; align-items: start; padding-bottom: 80px; }
.toc { position: sticky; top: 96px; padding: 20px; border: 1px solid var(--line); border-radius: 16px; background: var(--surface); font-size: 14px; }
.toc strong { display: block; margin-bottom: 10px; }
.toc ol { margin: 0; padding-left: 20px; }
.toc li + li { margin-top: 7px; }
.toc a { color: var(--muted); text-decoration: none; }
.toc a:hover { color: var(--accent); }
.article { min-width: 0; padding: 38px clamp(22px, 5vw, 64px); border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); box-shadow: var(--shadow); }
.article h2 { margin: 54px 0 16px; font-size: clamp(29px, 4vw, 40px); scroll-margin-top: 100px; }
.article h2:first-of-type { margin-top: 18px; }
.article h3 { margin: 32px 0 10px; font-size: 24px; }
.article p { margin: 0 0 18px; }
.article ul, .article ol { margin: 0 0 22px; padding-left: 26px; }
.article li + li { margin-top: 9px; }
.article figure { margin: 30px 0 36px; }
.article figure img { display: block; width: 100%; border: 1px solid #cbd6df; border-radius: 14px; background: #e7ecf1; box-shadow: 0 12px 32px rgba(24, 48, 70, .12); }
.article figcaption { margin-top: 10px; color: var(--muted); font-size: 14px; line-height: 1.5; }
.step { display: grid; grid-template-columns: 42px 1fr; gap: 14px; margin: 20px 0; }
.step-number { display: grid; place-items: center; width: 38px; height: 38px; border-radius: 50%; color: #fff; background: var(--accent); font-weight: 800; }
.step p { margin: 2px 0 0; }
.tip { margin: 24px 0; padding: 18px 20px; border-left: 4px solid var(--accent); border-radius: 0 12px 12px 0; background: var(--surface-alt); }
.tip p:last-child { margin-bottom: 0; }
.model-cloud { display: flex; flex-wrap: wrap; gap: 8px; margin: 20px 0 24px; }
.model-cloud span { padding: 7px 11px; border: 1px solid #c7d9e6; border-radius: 999px; background: #f5fbff; font-size: 14px; font-weight: 700; }
.checklist { list-style: none; padding-left: 0 !important; }
.checklist li { position: relative; padding-left: 34px; }
.checklist li::before { content: "✓"; position: absolute; left: 0; top: 0; color: #087a56; font-weight: 900; }
.warning-box { margin: 28px 0; padding: 20px; border: 1px solid #e2a1a1; border-radius: 14px; background: #fff1f1; }
.warning-box strong { color: #8b2424; }
.faq details { padding: 17px 0; border-top: 1px solid var(--line); }
.faq summary { cursor: pointer; font-weight: 800; }
.faq details p { margin: 10px 0 0; color: var(--muted); }
.next-guide { margin-top: 50px; padding: 25px; border-radius: 16px; color: #fff; background: var(--accent-dark); }
.next-guide h2 { margin: 0 0 10px; color: #fff; font-size: 28px; }
.next-guide p { margin-bottom: 0; color: #d9edf8; }

.site-footer { padding: 34px 0 48px; color: var(--muted); font-size: 14px; text-align: center; }
.breadcrumb { padding-top: 28px; color: var(--muted); font-size: 14px; }
.breadcrumb a { color: var(--muted); }

@media (max-width: 900px) {
  .card-grid { grid-template-columns: 1fr 1fr; }
  .article-shell { grid-template-columns: 1fr; }
  .toc { position: static; }
}
@media (max-width: 640px) {
  body { font-size: 17px; }
  .header-nav a:not(:last-child) { display: none; }
  .hero { padding-top: 48px; }
  .card-grid { grid-template-columns: 1fr; }
  .card.featured { grid-column: auto; }
  .article { padding-inline: 20px; }
  .notice { grid-template-columns: 1fr; }
  .quiet-link { display: none; }
  .start-hero { padding-top: 48px; }
  .start-card { grid-template-columns: 1fr; margin-top: 30px; }
  .guide-icon { width: 50px; height: 50px; border-radius: 14px; font-size: 25px; }
  .primary-button { width: 100%; }
  .path-list li { grid-template-columns: 38px 1fr; }
  .path-list em { grid-column: 2; }
}
@media print {
  .site-header, .toc, .site-footer { display: none; }
  body { background: #fff; font-size: 12pt; }
  .article-shell { display: block; }
  .article { border: 0; box-shadow: none; padding: 0; }
}