/* Light theme redesign */
* { box-sizing: border-box; }
:root {
  --bg: #f6f8fb;
  --ink: #1f2937;
  --muted: #6b7280;
  --primary: #2563eb;
  --primary-ink: #0b4ae2;
  --accent: #14b8a6;
  --warn: #f59e0b;
  --card: #ffffff;
  --border: #e5e7eb;
  --code: #0f172a;
  --code-bg: #f3f4f6;
}
html, body { height: 100%; }
body {
  margin: 0;
  font-family: 'Inter', system-ui, -apple-system, Segoe UI, Roboto, 'Helvetica Neue', Arial;
  color: var(--ink);
  background: var(--bg);
}
.container { max-width: 1100px; margin: 0 auto; padding: 24px; }

/* Header */
.site-header {
  position: sticky; top: 0; z-index: 20;
  border-bottom: 1px solid var(--border);
  background: rgba(255,255,255,.85);
  backdrop-filter: blur(8px);
}
.header-inner { display: flex; align-items: center; justify-content: space-between; gap: 16px; }
.brand { display: flex; align-items: center; gap: 10px; }
.logo-dot { width: 14px; height: 14px; border-radius: 50%; background: linear-gradient(135deg, var(--primary), var(--accent)); box-shadow: 0 0 0 4px rgba(37,99,235,.1); }
.brand-title { margin: 0; font-weight: 800; letter-spacing: .2px; }
.brand-subtitle { color: var(--muted); font-size: 14px; margin-left: 6px; }
.header-actions { display: flex; align-items: center; gap: 10px; }
.lang-toggle { cursor: pointer; border: 1px solid var(--border); background: #fff; color: var(--ink); padding: 8px 12px; border-radius: 999px; font-weight: 700; }
.lang-toggle:hover { border-color: #d1d5db; box-shadow: 0 1px 0 rgba(0,0,0,.03); }
.lang-toggle .divider { margin: 0 6px; color: var(--muted); }

/* Hero */
.hero { border-bottom: 1px solid var(--border); background: linear-gradient(180deg,#fff, #f8fafc); }
.hero-inner { display: grid; grid-template-columns: 1.3fr .9fr; gap: 24px; align-items: center; }
.hero-text h2 { margin: 8px 0 6px; font-size: 28px; }
.lead { color: var(--muted); margin: 8px 0 14px; }
.badges { display: flex; flex-wrap: wrap; gap: 8px; }
.badge { background: #eef2ff; color: var(--primary); padding: 6px 10px; border-radius: 999px; font-size: 12px; font-weight: 700; }
.hero-card { background: var(--card); border: 1px solid var(--border); border-radius: 16px; padding: 16px; box-shadow: 0 10px 30px rgba(0,0,0,.04); }
.tick-list { margin: 0; padding-left: 20px; }
.tick-list li { margin: 8px 0; }

/* TOC */
.toc { position: sticky; top: 66px; z-index: 10; border-bottom: 1px solid var(--border); background: #fff; }
.toc-inner { display: flex; gap: 16px; flex-wrap: wrap; }
.toc-link { display: inline-block; padding: 10px 14px; color: var(--ink); text-decoration: none; border-radius: 999px; }
.toc-link:hover { background: #f1f5f9; }

/* Cards */
.card { background: var(--card); border: 1px solid var(--border); border-radius: 16px; padding: 20px; margin: 24px 0; box-shadow: 0 10px 30px rgba(0,0,0,.04); }
.section-title { display: flex; align-items: baseline; gap: 10px; margin: 0 0 12px; }
.section-title .index { display: inline-flex; width: 28px; height: 28px; align-items: center; justify-content: center; border-radius: 8px; background: #eef2ff; color: var(--primary); font-weight: 800; }
.muted { color: var(--muted); margin: 8px 0 6px; font-weight: 600; }

/* Grids */
.grid.two { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 18px; }

/* Callouts */
.callout { border: 1px dashed #cbd5e1; background: #f8fafc; border-radius: 12px; padding: 10px 12px; margin: 10px 0; }

/* KPIs */
.kpi { display: grid; grid-template-columns: repeat(3,1fr); gap: 12px; background: #f8fafc; border: 1px solid var(--border); border-radius: 12px; padding: 10px; }
.kpi-num { font-size: 20px; font-weight: 800; color: var(--primary-ink); }
.kpi-label { color: var(--muted); font-size: 12px; }

/* Code */
pre { background: var(--code-bg); border: 1px solid var(--border); padding: 12px 14px; border-radius: 12px; overflow: auto; color: var(--code); }
code { font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace; }

/* Footer */
.site-footer { border-top: 1px solid var(--border); background: #fff; }
.footer-inner { display: flex; align-items: center; justify-content: space-between; gap: 10px; }
.footer-inner .product { color: var(--muted); }
.footer-inner .sep { margin: 0 6px; color: #cbd5e1; }
.footer-inner .links a { color: var(--muted); text-decoration: none; margin-left: 12px; }
.footer-inner .links a:hover { color: var(--ink); }

/* Language visibility */
.lang-en { display: none; }
body[data-lang="en"] .lang-zh { display: none !important; }
body[data-lang="en"] .lang-en { display: inline; }

/* CTA buttons */
.btn { display: inline-block; text-decoration: none; font-weight: 700; padding: 10px 14px; border-radius: 10px; border: 1px solid var(--border); }
.btn-primary { background: var(--primary); color: #fff; border-color: var(--primary); box-shadow: 0 8px 20px rgba(37,99,235,.2); }
.btn-primary:hover { background: var(--primary-ink); }
.btn-outline { background: #fff; color: var(--ink); }
.btn + .btn { margin-left: 10px; }
.cta { margin-top: 12px; }

/* Feature grid */
.feature-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 12px; }
.feature { background: #fff; border: 1px solid var(--border); border-radius: 12px; padding: 12px; }

/* Module cards */
.module-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 12px; }
.module-card { background: #fff; border: 1px solid var(--border); border-radius: 12px; padding: 12px; box-shadow: 0 10px 30px rgba(0,0,0,.04); }
.module-card h4 { margin: 6px 0 4px; }

/* Diagram */
.diagram { margin-top: 1rem; border: 1px dashed var(--border); border-radius: 12px; background: #fff; overflow: hidden; }
.diagram svg { width: 100%; height: auto; display: block; }

/* Back to top */
.to-top{ position: fixed; right: 20px; bottom: 24px; width: 44px; height: 44px; border-radius: 50%; background: var(--primary); color:#fff; border:none; box-shadow:0 6px 16px rgba(37,99,235,.28); cursor:pointer; display:none; align-items:center; justify-content:center; font-size:18px; }
.to-top.show{ display:flex; }
.to-top:hover{ background: #1d4ed8; }

/* Details/FAQ */
details{ border:1px solid var(--border); border-radius:12px; padding: .75rem 1rem; background:#fff; }
details+details{ margin-top:.75rem; }
details[open]{ box-shadow: var(--shadow); }
summary{ cursor:pointer; font-weight:600; }

/* Code blocks */
pre{ background:#0f172a; color:#e2e8f0; border-radius:12px; padding:1rem; overflow:auto; box-shadow: inset 0 0 0 1px rgba(148,163,184,.15); }
code{ font-family: ui-monospace,SFMono-Regular,Menlo,Consolas,monospace; font-size:.9rem; }

/* Spacing tweaks */
.card pre{ margin-top:.75rem; }
.module-card h4{ margin-bottom:.25rem; }
.feature strong{ color:#0f172a; }