:root {
  --primary: #6366f1;
  --primary-fg: #fff;
  --bg: #fff;
  --fg: #0f172a;
  --muted: #64748b;
  --muted-bg: #f1f5f9;
  --border: #e2e8f0;
  --card-bg: #fff;
  --sidebar-bg: #f8fafc;
  --code-bg: #1e293b;
  --code-fg: #e2e8f0;
  --radius: 8px;
  --font: 'Noto Sans SC', system-ui, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: var(--font);
  color: var(--fg);
  background: var(--bg);
  line-height: 1.6;
  font-size: 15px;
}

a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ── Header ── */
.header {
  position: sticky; top: 0; z-index: 50;
  height: 56px;
  border-bottom: 1px solid var(--border);
  background: rgba(255,255,255,0.95);
  backdrop-filter: blur(8px);
  display: flex; align-items: center;
}
.header-inner {
  max-width: 1200px; width: 100%; margin: 0 auto;
  padding: 0 24px;
  display: flex; align-items: center; justify-content: space-between; gap: 24px;
}
.logo { font-weight: 700; font-size: 17px; display: flex; align-items: center; gap: 2px; color: var(--fg); }
.logo .accent { color: var(--primary); }
.logo .dim { color: var(--muted); }
.header-nav { display: flex; gap: 20px; align-items: center; }
.header-nav a { font-size: 14px; color: var(--muted); }
.header-nav a:hover { color: var(--fg); text-decoration: none; }
.btn-primary {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 7px 16px; border-radius: var(--radius);
  background: var(--primary); color: var(--primary-fg);
  font-size: 14px; font-weight: 500; cursor: pointer;
  border: none;
}
.btn-primary:hover { opacity: 0.9; text-decoration: none; }
.btn-outline {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 7px 16px; border-radius: var(--radius);
  border: 1px solid var(--border); color: var(--fg);
  font-size: 14px; font-weight: 500; cursor: pointer;
  background: transparent;
}
.btn-outline:hover { background: var(--muted-bg); text-decoration: none; }

/* ── Layout ── */
.layout { display: flex; min-height: calc(100vh - 56px); }

/* ── Sidebar ── */
.sidebar {
  width: 224px; flex-shrink: 0;
  border-right: 1px solid var(--border);
  background: var(--sidebar-bg);
}
.sidebar-inner {
  position: sticky; top: 56px;
  height: calc(100vh - 56px);
  overflow-y: auto;
  padding: 16px 0;
}
.nav-group { margin-bottom: 16px; }
.nav-group-title {
  padding: 6px 16px;
  font-size: 11px; font-weight: 600;
  text-transform: uppercase; letter-spacing: .08em;
  color: var(--muted);
}
.nav-group-title span { color: var(--primary); margin-right: 4px; }
.nav-link {
  display: block; padding: 7px 16px;
  font-size: 13.5px; color: var(--muted);
  position: relative;
}
.nav-link:hover { color: var(--fg); background: var(--muted-bg); text-decoration: none; }
.nav-link.active {
  background: var(--primary); color: #fff; font-weight: 500;
}
.nav-link.active::before {
  content: ''; position: absolute; left: 0; top: 50%;
  transform: translateY(-50%);
  width: 3px; height: 16px;
  background: rgba(255,255,255,0.6); border-radius: 0 2px 2px 0;
}

/* ── Article ── */
.article-wrap { flex: 1; min-width: 0; }
article {
  max-width: 768px; margin: 0 auto;
  padding: 32px 24px 64px;
}

/* ── Breadcrumb ── */
.breadcrumb {
  display: flex; align-items: center; gap: 6px;
  font-size: 13px; color: var(--muted); margin-bottom: 24px;
}
.breadcrumb a { color: var(--muted); }
.breadcrumb a:hover { color: var(--fg); text-decoration: none; }
.breadcrumb .sep { color: var(--border); }
.breadcrumb .current { color: var(--fg); }

h1 { font-size: 28px; font-weight: 700; margin-bottom: 24px; line-height: 1.3; }
h2 { font-size: 19px; font-weight: 700; margin-bottom: 16px; margin-top: 40px; }
h2:first-of-type { margin-top: 0; }
h3 { font-size: 15px; font-weight: 600; margin-bottom: 8px; }
p { color: var(--muted); font-size: 14px; line-height: 1.7; }
section { margin-bottom: 32px; }

/* ── Cards ── */
.card {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card-bg);
  padding: 20px;
}
.card + .card { margin-top: 12px; }
.card h3 { color: var(--fg); }
.card p { margin-top: 4px; }

.card-grid { display: grid; gap: 16px; }
.card-grid.cols-2 { grid-template-columns: repeat(2, 1fr); }
.card-grid.cols-3 { grid-template-columns: repeat(3, 1fr); }
.card-grid.cols-4 { grid-template-columns: repeat(2, 1fr); }
@media (max-width: 640px) {
  .card-grid.cols-2, .card-grid.cols-3, .card-grid.cols-4 { grid-template-columns: 1fr; }
}

.card-icon {
  display: inline-flex; padding: 8px; border-radius: 8px;
  background: var(--muted-bg); margin-bottom: 12px; font-size: 20px;
}
.card.centered { text-align: center; }
.card.centered .card-icon { display: flex; justify-content: center; align-items: center; margin: 0 auto 12px; }

/* ── Intro card ── */
.intro-card {
  display: flex; gap: 20px; align-items: flex-start;
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--card-bg); padding: 20px; margin-bottom: 32px;
}
.intro-card-icon {
  width: 80px; height: 80px; flex-shrink: 0;
  border-radius: var(--radius); background: var(--muted-bg);
  display: flex; align-items: center; justify-content: center;
  font-size: 36px;
}
.intro-card p { font-size: 13.5px; }
.intro-card p + p { margin-top: 10px; }
.formula { font-weight: 700; color: var(--primary); font-size: 14px; }

/* ── Formula box ── */
.formula-box {
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--card-bg); padding: 20px; text-align: center;
  font-size: 16px; font-weight: 700;
}
.formula-box .accent { color: var(--primary); }

/* ── Table ── */
.table-wrap { overflow-x: auto; border-radius: var(--radius); border: 1px solid var(--border); }
table { width: 100%; border-collapse: collapse; font-size: 13.5px; }
thead tr { background: var(--primary); color: var(--primary-fg); }
th { padding: 10px 14px; text-align: left; font-weight: 600; }
td { padding: 10px 14px; border-bottom: 1px solid var(--border); color: var(--muted); }
td:first-child { color: var(--fg); font-weight: 500; }
tbody tr:nth-child(even) { background: var(--muted-bg); }

/* ── Code Block ── */
.code-block {
  border-radius: var(--radius); overflow: hidden;
  margin: 16px 0;
}
.code-header {
  background: #0f172a; padding: 8px 14px;
  font-size: 12px; color: #94a3b8;
  display: flex; align-items: center; gap: 6px;
}
.code-header .lang { color: var(--primary); font-weight: 600; }
pre {
  background: var(--code-bg);
  padding: 16px;
  overflow-x: auto;
  margin: 0;
}
code {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--code-fg);
}
p code, li code {
  background: var(--muted-bg);
  color: var(--primary);
  padding: 1px 5px;
  border-radius: 4px;
  font-size: 12px;
}

/* ── Note / Callout ── */
.note {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: #f0f4ff;
  padding: 14px 18px;
  font-size: 13.5px;
  margin: 16px 0;
}
.note.secondary { background: var(--muted-bg); }
.note h4 { font-size: 14px; margin-bottom: 6px; color: var(--fg); }
.note ul, .note ol { padding-left: 18px; }
.note li { color: var(--muted); font-size: 13.5px; margin: 3px 0; }

/* ── Steps ── */
.steps { display: flex; flex-direction: column; gap: 0; }
.step { display: flex; gap: 16px; padding: 16px; border: 1px solid var(--border); background: var(--card-bg); }
.step:first-child { border-radius: var(--radius) var(--radius) 0 0; }
.step:last-child { border-radius: 0 0 var(--radius) var(--radius); border-top: none; }
.step + .step { border-top: none; }
.step-num {
  width: 32px; height: 32px; flex-shrink: 0;
  background: var(--primary); color: #fff;
  border-radius: 50%; display: flex; align-items: center; justify-content: center;
  font-size: 13px; font-weight: 700;
}
.step-num.muted { background: var(--muted-bg); color: var(--fg); }
.step h3 { color: var(--fg); font-size: 14px; }
.step p { font-size: 13px; margin-top: 2px; }

/* ── Flow ── */
.flow { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; padding: 20px; border: 1px solid var(--border); border-radius: var(--radius); background: var(--card-bg); margin-bottom: 16px; }
.flow-item { padding: 8px 14px; border-radius: 6px; font-size: 13px; font-weight: 500; background: var(--muted-bg); }
.flow-item.primary { background: var(--primary); color: #fff; }
.flow-arrow { color: var(--muted); font-size: 18px; }

/* ── Vertical flow ── */
.vflow { max-width: 400px; margin: 0 auto; }
.vflow-item { text-align: center; padding: 10px; border-radius: 6px; font-size: 13px; font-weight: 500; background: var(--muted-bg); }
.vflow-item.primary { background: var(--primary); color: #fff; }
.vflow-sep { width: 2px; height: 16px; background: var(--border); margin: 0 auto; }

/* ── Feature cards on home ── */
.feature-card {
  display: block;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card-bg);
  padding: 20px;
  transition: border-color .15s, box-shadow .15s;
}
.feature-card:hover { border-color: rgba(99,102,241,.4); box-shadow: 0 2px 8px rgba(0,0,0,.06); text-decoration: none; }
.feature-card .card-icon { background: var(--muted-bg); font-size: 22px; }
.feature-card h3 { font-size: 15px; color: var(--fg); margin-bottom: 6px; }
.feature-card p { font-size: 13px; margin: 0; }

/* ── Hero ── */
.hero { padding: 64px 24px; text-align: center; }
.hero-badge {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 5px 12px; border-radius: 99px;
  background: var(--muted-bg); color: var(--fg);
  font-size: 13px; margin-bottom: 24px;
}
.hero h1 { font-size: clamp(28px, 5vw, 50px); max-width: 700px; margin: 0 auto 20px; }
.hero h1 .accent { color: var(--primary); }
.hero p { font-size: 16px; max-width: 560px; margin: 0 auto 28px; color: var(--muted); }
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; justify-content: center; }
.hero-actions .btn-primary, .hero-actions .btn-outline { padding: 10px 22px; font-size: 15px; }

/* ── CTA ── */
.cta {
  padding: 64px 24px; text-align: center;
  background: rgba(99,102,241,.04);
}
.cta h2 { font-size: 24px; margin-bottom: 12px; }
.cta p { font-size: 15px; max-width: 480px; margin: 0 auto 24px; color: var(--muted); }

/* ── Footer ── */
footer {
  border-top: 1px solid var(--border);
  padding: 24px;
  font-size: 13px; color: var(--muted);
  text-align: center;
}

/* ── Page nav ── */
.page-nav {
  display: flex; justify-content: space-between; align-items: center;
  padding-top: 24px; margin-top: 32px;
  border-top: 1px solid var(--border);
  gap: 12px;
}
.page-nav .spacer { flex: 1; }

/* ── Resources ── */
.resource-link {
  display: flex; justify-content: space-between; align-items: flex-start; gap: 12px;
  padding: 14px 16px; border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--card-bg); margin-bottom: 8px; color: inherit;
}
.resource-link:hover { border-color: rgba(99,102,241,.4); text-decoration: none; }
.resource-link h3 { font-size: 14px; color: var(--fg); margin-bottom: 4px; }
.resource-link p { font-size: 13px; margin: 0; }
.resource-link .ext { color: var(--muted); flex-shrink: 0; margin-top: 2px; }

/* ── Pill list ── */
ol, ul { padding-left: 20px; }
li { color: var(--muted); font-size: 14px; margin: 4px 0; }

/* ── Quick start box ── */
.quick-start {
  border: 1px solid rgba(99,102,241,.35);
  border-radius: var(--radius);
  background: rgba(99,102,241,.05);
  padding: 16px 20px;
  margin-bottom: 32px;
}
.quick-start strong { color: var(--fg); display: block; margin-bottom: 4px; }
.quick-start p { font-size: 13.5px; }

/* ── Coming soon ── */
.coming-soon {
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--card-bg); padding: 48px 24px; text-align: center;
}
.coming-soon p { font-size: 14px; }
.coming-soon p + p { margin-top: 6px; }

/* ── React/highlight.js theme override ── */
.hljs { background: var(--code-bg) !important; padding: 0 !important; }

@media (max-width: 960px) {
  .sidebar { display: none; }
  .card-grid.cols-3 { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 640px) {
  article { padding: 24px 16px 48px; }
  h1 { font-size: 22px; }
  .intro-card { flex-direction: column; }
  .header-nav { display: none; }
  .flow { flex-direction: column; align-items: flex-start; }
}