/* base.css — theme-agnostic skeleton */
:root{
  --bg:#ffffff; --surface:#f6f7f9; --text:#151515; --muted:#6b7280;
  --line:#e7e8ec; --accent:#FF4F47; --accent-soft:rgba(255,79,71,.10);
  --accent-dark:#d13a34;
  --radius:14px; --maxw:1080px;
  --font-en:-apple-system,BlinkMacSystemFont,'SF Pro Display','Segoe UI',sans-serif;
  --font-zh:'PingFang SC','Noto Sans SC',sans-serif;
  --font:var(--font-en),var(--font-zh);
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{background:var(--bg);color:var(--text);font-family:var(--font);
  line-height:1.6;-webkit-font-smoothing:antialiased}
.deck{max-width:var(--maxw);margin:0 auto;padding:0 24px}
.section{padding:64px 0;border-top:1px solid var(--line)}
.section:first-of-type{border-top:none}
.chunk{margin:24px 0}
.eyebrow{font-size:12px;letter-spacing:.14em;text-transform:uppercase;
  color:var(--accent);font-weight:700;margin-bottom:10px}
h1{font-size:clamp(30px,5vw,52px);line-height:1.15;font-weight:700;letter-spacing:-.01em}
h2{font-size:clamp(22px,3vw,34px);line-height:1.25;font-weight:700;margin-bottom:10px;letter-spacing:-.01em}
h3{font-size:19px;font-weight:600;margin-bottom:6px}
p{color:var(--text);max-width:64ch}
.muted{color:var(--muted)}
.grid-2{display:grid;gap:20px;grid-template-columns:repeat(2,1fr)}
.grid-3{display:grid;gap:20px;grid-template-columns:repeat(3,1fr)}
.grid-4{display:grid;gap:16px;grid-template-columns:repeat(4,1fr)}
@media(max-width:760px){.grid-2,.grid-3,.grid-4{grid-template-columns:1fr}}

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

/* --- components --- */
.stat{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:22px}
.stat-n{font-size:34px;font-weight:800;color:var(--accent);line-height:1;letter-spacing:-.02em}
.stat-l{font-size:13px;color:var(--muted);margin-top:8px;font-weight:500}
.table-wrap{overflow-x:auto;border:1px solid var(--line);border-radius:var(--radius);background:#fff}
table{width:100%;border-collapse:collapse;font-size:14px}
th,td{padding:12px 14px;text-align:left;border-bottom:1px solid var(--line);vertical-align:top}
th{background:var(--surface);font-weight:600;font-size:13px;letter-spacing:.02em;text-transform:uppercase;color:var(--muted)}
tr:last-child td{border-bottom:none}
.gantt{display:flex;flex-direction:column;gap:10px}
.gantt-row{display:grid;grid-template-columns:160px 1fr;align-items:center;gap:12px}
@media(max-width:760px){.gantt-row{grid-template-columns:100px 1fr}}
.gantt-track{position:relative;height:28px;background:var(--surface);border-radius:999px;border:1px solid var(--line)}
.gantt-bar{position:absolute;top:0;height:26px;border-radius:999px;background:var(--accent);
  display:flex;align-items:center;padding:0 12px;color:#fff;font-size:12px;white-space:nowrap;font-weight:600}
.gantt-bar.soft{background:var(--accent-soft);color:var(--accent)}
.flow{display:grid;gap:14px;grid-template-columns:repeat(auto-fit,minmax(180px,1fr))}
.flow-step{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:18px}
.flow-step .n{width:28px;height:28px;border-radius:50%;background:var(--accent);color:#fff;
  display:flex;align-items:center;justify-content:center;font-size:14px;font-weight:700;margin-bottom:10px}
.flow-step h3{margin-bottom:4px}
.flow-step p{font-size:14px}
.tier{border:1px solid var(--line);border-radius:var(--radius);padding:24px;background:var(--bg);transition:transform .15s ease,border-color .15s ease}
.tier:hover{border-color:var(--accent);transform:translateY(-2px)}
.tier .price{font-size:28px;font-weight:700;margin:8px 0;letter-spacing:-.01em}
.quote{border-left:3px solid var(--accent);padding:8px 0 8px 18px;font-size:18px;font-style:italic;color:var(--text);max-width:64ch}
.callout{background:var(--accent-soft);border:1px solid var(--line);border-radius:var(--radius);padding:22px}
.callout strong{color:var(--accent-dark)}
.pill{display:inline-block;padding:5px 14px;border-radius:999px;background:var(--accent-soft);
  color:var(--accent);font-size:12px;font-weight:700;letter-spacing:.03em}
.pill.dark{background:var(--text);color:#fff}
.pill.outline{background:transparent;border:1px solid var(--accent);color:var(--accent)}

/* --- nav card (hub) --- */
.nav-card{display:block;padding:32px 28px;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);text-decoration:none;color:var(--text);transition:all .18s ease;position:relative;overflow:hidden}
.nav-card:hover{border-color:var(--accent);background:#fff;transform:translateY(-3px);box-shadow:0 10px 30px rgba(255,79,71,.08);text-decoration:none}
.nav-card .num{font-size:12px;color:var(--muted);font-weight:600;letter-spacing:.14em}
.nav-card h3{font-size:22px;margin:12px 0 8px;color:var(--text)}
.nav-card p{font-size:14px;color:var(--muted)}
.nav-card .arrow{position:absolute;top:24px;right:24px;color:var(--accent);font-size:20px;transition:transform .18s ease}
.nav-card:hover .arrow{transform:translateX(4px)}

/* --- back link --- */
.back-link{display:inline-flex;align-items:center;gap:6px;padding:8px 14px;background:var(--surface);border:1px solid var(--line);border-radius:999px;font-size:13px;font-weight:600;color:var(--text)}
.back-link:hover{background:var(--accent-soft);border-color:var(--accent);color:var(--accent);text-decoration:none}

/* --- lifetime warranty banner --- */
.warranty-banner{background:linear-gradient(135deg,var(--text) 0%,#2a2a2f 100%);color:#fff;border-radius:var(--radius);padding:32px 28px;position:relative;overflow:hidden}
.warranty-banner::before{content:"⚡";position:absolute;top:-20px;right:-10px;font-size:120px;opacity:.1}
.warranty-banner h3{color:#fff;font-size:22px;margin-bottom:10px}
.warranty-banner p{color:rgba(255,255,255,.85);max-width:64ch}
.warranty-banner .pill{background:var(--accent);color:#fff}

/* --- checklist --- */
.checklist{list-style:none;padding:0}
.checklist li{padding:10px 0 10px 32px;position:relative;font-size:15px;border-bottom:1px solid var(--line)}
.checklist li:last-child{border-bottom:none}
.checklist li::before{content:"✓";position:absolute;left:0;top:10px;width:22px;height:22px;background:var(--accent-soft);color:var(--accent);border-radius:50%;display:flex;align-items:center;justify-content:center;font-weight:700;font-size:13px}

/* --- side-by-side option toggle --- */
.option-card{border:2px solid var(--line);border-radius:var(--radius);padding:28px;background:var(--bg);transition:border-color .18s ease}
.option-card.recommended{border-color:var(--accent)}
.option-card h3{font-size:22px;margin-bottom:6px}
.option-card .sub{font-size:14px;color:var(--muted);margin-bottom:20px}
.option-card table{margin-top:8px}
.option-card th{background:transparent;padding:8px 0;font-size:12px}
.option-card td{padding:10px 0;font-size:14px}
.option-card .badge{display:inline-block;background:var(--accent);color:#fff;padding:3px 10px;font-size:11px;border-radius:999px;font-weight:700;margin-left:8px;vertical-align:middle;letter-spacing:.03em}

/* --- key term row --- */
.term-row{display:grid;grid-template-columns:180px 1fr;gap:16px;padding:14px 0;border-bottom:1px solid var(--line)}
.term-row:last-child{border-bottom:none}
.term-row .k{font-weight:600;color:var(--muted);font-size:13px;letter-spacing:.02em;text-transform:uppercase}
.term-row .v{font-size:15px;line-height:1.55}
@media(max-width:640px){.term-row{grid-template-columns:1fr}}

/* --- footer --- */
footer.section{text-align:center;padding:48px 0;border-top:1px solid var(--line)}
footer.section p{max-width:none;margin:14px auto 0}
footer.section .pill{margin:0 auto}

/* --- table cell emphasis --- */
td strong{color:var(--accent-dark)}
.no-wrap{white-space:nowrap}
.mono{font-family:ui-monospace,'SF Mono',Menlo,Consolas,monospace}

/* --- hero tag --- */
.hero-tag{display:inline-block;padding:6px 14px;background:var(--accent-soft);color:var(--accent);border-radius:999px;font-size:12px;font-weight:700;letter-spacing:.06em;text-transform:uppercase;margin-bottom:18px}

/* --- decision box --- */
.decision-box{background:#fff;border:2px solid var(--accent);border-radius:var(--radius);padding:28px;position:relative}
.decision-box::before{content:"决策";position:absolute;top:-12px;left:20px;background:var(--accent);color:#fff;padding:2px 12px;font-size:11px;border-radius:999px;font-weight:700;letter-spacing:.08em}
.decision-box h3{margin-bottom:14px}

/* --- badge inline --- */
.badge-refund{display:inline-block;background:#dcfce7;color:#166534;padding:2px 8px;font-size:11px;border-radius:6px;font-weight:700;letter-spacing:.02em;margin-left:6px;vertical-align:middle}

/* --- floating scroll-to-top button --- */
.scroll-top{
  position:fixed;bottom:24px;right:24px;
  width:52px;height:52px;border-radius:50%;
  background:#fff;border:1px solid var(--line);
  color:var(--accent);font-size:22px;font-weight:700;
  cursor:pointer;padding:0;line-height:1;
  box-shadow:0 4px 20px rgba(0,0,0,.10);
  display:flex;align-items:center;justify-content:center;
  transition:transform .18s ease,box-shadow .18s ease,background .18s ease,color .18s ease,border-color .18s ease;
  z-index:100;
  font-family:var(--font)
}
.scroll-top:hover{
  transform:translateY(-2px);
  box-shadow:0 8px 24px rgba(255,79,71,.25);
  background:var(--accent);color:#fff;border-color:var(--accent)
}
.scroll-top:active{transform:translateY(0)}
@media(max-width:640px){
  .scroll-top{bottom:16px;right:16px;width:48px;height:48px;font-size:20px}
}

/* --- citation superscript --- */
sup.cite{font-size:10px;font-weight:700;color:var(--accent);vertical-align:super;line-height:0;margin-left:2px}
sup.cite a{color:var(--accent);text-decoration:none;padding:1px 4px;background:var(--accent-soft);border-radius:4px}
sup.cite a:hover{background:var(--accent);color:#fff;text-decoration:none}
.ref-list{list-style:none;padding:0;counter-reset:refnum}
.ref-list li{padding:8px 0 8px 32px;position:relative;font-size:13px;border-bottom:1px solid var(--line);counter-increment:refnum}
.ref-list li::before{content:"[" counter(refnum) "]";position:absolute;left:0;top:8px;color:var(--accent);font-weight:700;font-size:12px}
.ref-list li:last-child{border-bottom:none}
.ref-list a{word-break:break-all}
.src-line{font-size:12px;color:var(--muted);margin-top:6px;font-style:italic}
.src-line a{color:var(--muted);border-bottom:1px dotted var(--muted)}
.src-line a:hover{color:var(--accent);border-color:var(--accent);text-decoration:none}