:root {
    --bg: #f5f7fa;
    --surface: #ffffff;
    --border: #e4e8ef;
    --text: #1f2933;
    --muted: #6b7785;
    --accent: #2563eb;
    --accent-hover: #1d4ed8;
    --accent-soft: #eaf1ff;
    --shadow: 0 1px 3px rgba(16, 24, 40, .08), 0 1px 2px rgba(16, 24, 40, .06);
    --shadow-lg: 0 10px 30px rgba(16, 24, 40, .12);
    --grid: rgba(37, 99, 235, .07);
    --maxw: 1120px;
  }
  :root[data-theme="dark"] {
    --bg: #0f172a;
    --surface: #1e293b;
    --border: #334155;
    --text: #e2e8f0;
    --muted: #94a3b8;
    --accent: #3b82f6;
    --accent-hover: #60a5fa;
    --accent-soft: #1e3a8a;
    --shadow: 0 1px 3px rgba(0, 0, 0, .4);
    --shadow-lg: 0 10px 30px rgba(0, 0, 0, .5);
    --grid: rgba(96, 165, 250, .09);
  }

  * { box-sizing: border-box; }
  html { scroll-behavior: smooth; }
  body {
    margin: 0;
    background: var(--bg);
    color: var(--text);
    font-family: system-ui, -apple-system, "Segoe UI", "PingFang TC", "Microsoft JhengHei", "Helvetica Neue", Arial, sans-serif;
    line-height: 1.75;
    -webkit-font-smoothing: antialiased;
    transition: background .2s ease, color .2s ease;
  }
  a { color: var(--accent); text-decoration: none; }
  h1, h2, h3 { line-height: 1.2; margin: 0; letter-spacing: -.01em; }
  p { margin: 0; }
  ul { margin: 0; padding: 0; list-style: none; }
  .wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }
  .skip { position: absolute; left: -9999px; }
  .skip:focus { left: 12px; top: 12px; z-index: 100; background: var(--surface); padding: 10px 16px; border-radius: 10px; }

  /* ---------- Header ---------- */
  .hdr {
    position: sticky; top: 0; z-index: 50;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    transition: box-shadow .2s ease;
  }
  .hdr.stuck { box-shadow: var(--shadow); }
  .hdr-in {
    max-width: var(--maxw); margin: 0 auto; padding: 12px 20px;
    display: flex; align-items: center; gap: 24px;
  }
  .brand { display: flex; align-items: center; gap: 9px; color: var(--text); }
  .brand svg { display: block; flex-shrink: 0; }
  .brand b { font-size: 19px; font-weight: 800; letter-spacing: -.02em; }
  .brand span { font-size: 12px; color: var(--muted); font-weight: 500; padding-left: 9px; border-left: 1px solid var(--border); line-height: 1.2; }
  .hdr-ctl { display: flex; align-items: center; gap: 8px; margin-left: auto; }
  select, .theme-btn {
    font: inherit; font-size: 13.5px;
    background: var(--bg); color: var(--text);
    border: 1px solid var(--border); border-radius: 999px;
    cursor: pointer; transition: border-color .15s ease;
  }
  select { padding: 7px 8px; }
  .theme-btn { width: 36px; height: 36px; display: grid; place-items: center; font-size: 16px; padding: 0; }
  select:hover, .theme-btn:hover { border-color: var(--accent); }
  :focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 4px; }

  /* ---------- Hero ---------- */
  .hero { position: relative; overflow: hidden; padding: 92px 0 76px; }
  .hero::before {
    content: ""; position: absolute; inset: 0; pointer-events: none;
    background:
      radial-gradient(760px 380px at 22% -8%, var(--accent-soft), transparent 70%),
      linear-gradient(to bottom, transparent 55%, var(--bg) 100%);
  }
  .hero::after {
    content: ""; position: absolute; inset: 0; pointer-events: none;
    background-image:
      linear-gradient(to right, var(--grid) 1px, transparent 1px),
      linear-gradient(to bottom, var(--grid) 1px, transparent 1px);
    background-size: 56px 56px;
    -webkit-mask-image: radial-gradient(620px 340px at 30% 0%, #000 10%, transparent 78%);
    mask-image: radial-gradient(620px 340px at 30% 0%, #000 10%, transparent 78%);
  }
  .hero-in { position: relative; z-index: 1; max-width: 780px; }
  h1 { font-size: clamp(2rem, 4.6vw, 3.2rem); font-weight: 800; margin-bottom: 20px; }
  .lede { font-size: clamp(15.5px, 1.7vw, 17.5px); color: var(--muted); max-width: 640px; }
  .cta-row { display: flex; flex-wrap: wrap; gap: 12px; margin: 34px 0 0; }
  .btn {
    display: inline-flex; align-items: center; gap: 9px;
    padding: 13px 24px; border-radius: 999px;
    font-size: 15px; font-weight: 600; line-height: 1;
    border: 1px solid transparent; transition: all .18s ease;
  }
  .btn svg { transition: transform .18s ease; }
  .btn-pri { background: var(--accent); color: #fff; box-shadow: 0 4px 14px rgba(37, 99, 235, .25); }
  .btn-pri:hover { background: var(--accent-hover); transform: translateY(-1px); box-shadow: 0 8px 22px rgba(37, 99, 235, .32); }
  .btn-pri:hover svg { transform: translateX(3px); }
  .btn-sec { background: var(--surface); color: var(--text); border-color: var(--border); }
  .btn-sec:hover { border-color: var(--accent); color: var(--accent); transform: translateY(-1px); }
  .btn-sec:hover svg { transform: translateX(3px); }

  /* ---------- Section ---------- */
  section { padding: 76px 0; }
  .sec-head { margin-bottom: 38px; }
  .kicker { font-size: 12.5px; font-weight: 700; letter-spacing: .1em; text-transform: uppercase; color: var(--accent); margin-bottom: 10px; }
  h2 { font-size: clamp(1.5rem, 3vw, 2rem); font-weight: 700; margin-bottom: 10px; }
  .sec-desc { color: var(--muted); font-size: 15.5px; max-width: 620px; }

  /* ---------- Product cards ---------- */
  .pgrid { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; }
  .pcard {
    position: relative; display: flex; flex-direction: column;
    background: var(--surface); border: 1px solid var(--border);
    border-radius: 18px; padding: 28px;
    box-shadow: var(--shadow);
    transition: transform .18s ease, box-shadow .18s ease, border-color .18s ease;
  }
  .pcard::before {
    content: ""; position: absolute; left: 28px; right: 28px; top: -1px; height: 2px;
    background: linear-gradient(90deg, var(--accent), transparent);
    border-radius: 2px; opacity: 0; transition: opacity .18s ease;
  }
  .pcard:hover { transform: translateY(-2px); box-shadow: var(--shadow-lg); border-color: color-mix(in srgb, var(--accent) 45%, var(--border)); }
  .pcard:hover::before { opacity: 1; }
  .pcard-top { display: flex; align-items: center; gap: 12px; margin-bottom: 20px; }
  .picon {
    width: 46px; height: 46px; border-radius: 13px;
    display: grid; place-items: center; font-size: 23px;
    background: var(--accent-soft); flex-shrink: 0;
  }
  .badge {
    font-size: 12px; font-weight: 600; color: var(--muted);
    border: 1px solid var(--border); border-radius: 999px; padding: 4px 11px;
    line-height: 1.5;
  }
  .pcard h3 { font-size: 22px; font-weight: 700; margin-bottom: 9px; }
  .pdesc { color: var(--muted); font-size: 14.5px; margin-bottom: 20px; }
  .plist { display: grid; gap: 9px; margin-bottom: 20px; }
  .plist li { position: relative; padding-left: 24px; font-size: 14.5px; }
  .plist li::before {
    content: ""; position: absolute; left: 4px; top: 9px;
    width: 6px; height: 6px; border-radius: 50%;
    background: var(--accent); opacity: .75;
  }
  .chips { display: flex; flex-wrap: wrap; gap: 7px; margin-bottom: 20px; }
  .chip {
    font-size: 12.5px; color: var(--text); background: var(--bg);
    border: 1px solid var(--border); border-radius: 999px; padding: 4px 11px;
  }
  .pfoot {
    display: flex; align-items: center; justify-content: space-between; gap: 16px;
    margin-top: auto; padding-top: 18px; border-top: 1px solid var(--border);
  }
  .pmeta { font-size: 12.5px; color: var(--muted); font-variant-numeric: tabular-nums; }
  .pcta { display: inline-flex; align-items: center; gap: 6px; font-size: 14.5px; font-weight: 600; white-space: nowrap; }
  .pcta svg { transition: transform .18s ease; }
  .pcard:hover .pcta svg { transform: translateX(3px); }

  /* ---------- Footer ---------- */
  .ftr { border-top: 1px solid var(--border); padding: 54px 0 26px; }
  .fgrid { display: grid; grid-template-columns: 1.6fr 1fr; gap: 40px; }
  .ftr .brand { margin-bottom: 12px; }
  .ftr-tag { color: var(--muted); font-size: 14px; max-width: 280px; }
  .fcol h4 { font-size: 12.5px; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--muted); margin: 0 0 14px; }
  .fcol ul { display: grid; gap: 10px; }
  .fcol a { color: var(--text); font-size: 14.5px; }
  .fcol a:hover { color: var(--accent); }
  .fbot {
    display: flex; flex-wrap: wrap; gap: 12px; justify-content: space-between;
    margin-top: 44px; padding-top: 20px; border-top: 1px solid var(--border);
    font-size: 12.5px; color: var(--muted);
  }

  /* ---------- Responsive ---------- */
  @media (max-width: 900px) {
    .pgrid { grid-template-columns: 1fr; }
    .fgrid { grid-template-columns: 1fr 1fr; }
    .ftr-tag { max-width: none; }
  }
  @media (max-width: 760px) {
    .brand span { display: none; }
    .hero { padding: 62px 0 52px; }
    section { padding: 56px 0; }
    .cta-row .btn { flex: 1 1 100%; justify-content: center; }
    .pcard { padding: 22px; }
    .pcard::before { left: 22px; right: 22px; }
    .pfoot { flex-direction: column; align-items: flex-start; gap: 10px; }
    .fgrid { grid-template-columns: 1fr; gap: 30px; }
  }
  @media (prefers-reduced-motion: reduce) {
    html { scroll-behavior: auto; }
    * { transition: none !important; }
  }

/* ---------- 404 ---------- */
.err {
  min-height: 100vh;
  display: flex; flex-direction: column;
  justify-content: center; align-items: center;
  text-align: center; padding: 48px 20px;
}
.err-brand {
  display: inline-flex; align-items: center; gap: 9px;
  color: var(--text); font-weight: 800; font-size: 19px;
  letter-spacing: -.02em; margin-bottom: 36px;
}
.err-code {
  font-size: clamp(64px, 12vw, 104px); font-weight: 800;
  line-height: 1; letter-spacing: -.04em; margin: 0;
  color: var(--accent); opacity: .16;
}
.err h1 { font-size: clamp(1.35rem, 3vw, 1.75rem); margin: 14px 0 12px; }
.err-desc { color: var(--muted); font-size: 15px; margin-bottom: 30px; }
.err-actions { display: flex; gap: 12px; flex-wrap: wrap; justify-content: center; }