/* ============================================================
   天下为公 TIANXIA.PUB — 设计系统
   「一卷天下 · 铁笔红章」：宣纸底 + 徽墨字 + 公章红 + 靛蓝算力
   ============================================================ */
:root{
  --paper:#f7f4ec;
  --paper-2:#fbf9f3;
  --card:#ffffff;
  --ink:#1c1a17;
  --ink-2:#4a453d;
  --ink-3:#857d70;
  --line:#e2dbcb;
  --line-2:#efe9dc;

  --seal:#b3241c;          /* 公章红 */
  --seal-deep:#8a1a14;
  --seal-tint:rgba(179,36,28,.07);
  --indigo:#1f3a5f;        /* 算力靛蓝 */
  --indigo-2:#2e5580;
  --indigo-tint:rgba(31,58,95,.07);
  --gold:#b98a2e;

  --radius:14px;
  --radius-sm:9px;
  --maxw:1160px;
  --nav-h:66px;
  --shadow:0 1px 2px rgba(28,26,23,.04),0 8px 24px -12px rgba(28,26,23,.18);
  --sans:"Microsoft YaHei","PingFang SC","Noto Sans CJK SC","Source Han Sans SC","WenQuanYi Micro Hei",Arial,"Helvetica Neue",system-ui,sans-serif;
  --sans:"Inter","Helvetica Neue","PingFang SC","Microsoft YaHei",system-ui,sans-serif;
  --mono:"JetBrains Mono","SFMono-Regular",Menlo,Consolas,monospace;
}
*{margin:0;padding:0;box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{
  font-family:var(--sans);background:var(--paper);color:var(--ink);
  line-height:1.85;font-size:16.5px;font-weight:400;
  -webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility;
  background-image:
    radial-gradient(circle at 12% 8%,rgba(179,36,28,.045),transparent 42%),
    radial-gradient(circle at 88% 92%,rgba(31,58,95,.05),transparent 45%);
  background-attachment:fixed;
}
img{max-width:100%;display:block}
a{color:inherit;text-decoration:none}
::selection{background:rgba(179,36,28,.16)}

/* ---------- 顶栏 ---------- */
.nav{
  position:fixed;top:0;left:0;right:0;z-index:120;
  background:rgba(247,244,236,.9);backdrop-filter:blur(12px) saturate(1.4);
  border-bottom:1px solid var(--line);
}
.nav-inner{
  max-width:var(--maxw);margin:0 auto;padding:0 22px;
  display:flex;align-items:center;gap:14px;min-height:var(--nav-h);flex-wrap:wrap;
}
.brand{display:flex;align-items:center;gap:11px;margin-right:auto;padding:8px 0}
.brand img{height:40px;width:40px;flex:none}
.brand .bname{font-weight:700;font-size:20px;letter-spacing:3px;color:var(--ink)}
.brand .bsub{display:block;font-family:var(--sans);font-size:10.5px;letter-spacing:2.6px;color:var(--ink-3);font-weight:500;margin-top:-3px}
.menu{display:flex;align-items:center;gap:6px;flex-wrap:wrap}
.menu a{
  padding:7px 13px;border-radius:999px;font-size:14.5px;color:var(--ink-2);
  line-height:1.4;transition:background .18s,color .18s;
}
.menu a:hover{background:var(--seal-tint);color:var(--seal-deep)}
.menu a.on{color:var(--seal-deep);font-weight:700;background:var(--seal-tint)}
.menu a.cta{background:var(--seal);color:#fff;font-weight:600}
.menu a.cta:hover{background:var(--seal-deep);color:#fff}

/* ---------- 布局 ---------- */
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 22px}
main{padding-top:var(--nav-h)}
section.band{padding:76px 0}
section.band.tight{padding:52px 0}
.alt{background:linear-gradient(180deg,rgba(255,255,255,.65),rgba(255,255,255,0))}
.dark{
  background:linear-gradient(150deg,#161513,#201e1a 55%,#1a2432);
  color:#f0ece2;
}
.dark h2,.dark h3{color:#fbf7ee}
.dark p{color:#cfc7b8}
.dark .muted{color:#9c9284}

.eyebrow{
  font-family:var(--sans);font-size:12px;letter-spacing:3.2px;font-weight:600;
  color:var(--seal);text-transform:uppercase;margin-bottom:12px;
  display:flex;align-items:center;gap:9px;
}
.eyebrow::before{content:"";width:22px;height:1px;background:var(--seal);opacity:.6}
.dark .eyebrow{color:#e0796f}
.dark .eyebrow::before{background:#e0796f}

h1,h2,h3,h4{line-height:1.35;letter-spacing:.5px}
h1{font-size:clamp(30px,4.6vw,54px);font-weight:700;letter-spacing:2px}
h2{font-size:clamp(24px,3vw,34px);font-weight:700;letter-spacing:1.5px}
h3{font-size:19px;font-weight:700;letter-spacing:.8px}
h4{font-size:16px;font-weight:700}
.lead{font-size:clamp(16px,1.5vw,19px);color:var(--ink-2);line-height:1.95;max-width:64ch}
.muted{color:var(--ink-3)}
.center{text-align:center}
.center .lead{margin-left:auto;margin-right:auto}
.center .eyebrow{justify-content:center}

/* ---------- 首屏 ---------- */
.hero{position:relative;overflow:hidden;padding:64px 0 72px;border-bottom:1px solid var(--line)}
.hero-grid{display:grid;grid-template-columns:1.06fr .94fr;gap:52px;align-items:center}
.hero h1{margin-bottom:20px}
.hero h1 .hl{color:var(--seal)}
.hero .kicker{
  display:inline-flex;align-items:center;gap:8px;font-family:var(--sans);
  font-size:12px;letter-spacing:1.8px;color:var(--indigo);
  background:var(--indigo-tint);border:1px solid rgba(31,58,95,.16);
  padding:5px 13px;border-radius:999px;margin-bottom:20px;font-weight:600;
}
.hero .kicker i{width:6px;height:6px;border-radius:50%;background:var(--seal);display:block}
.btn-row{display:flex;gap:12px;flex-wrap:wrap;margin-top:28px}
.btn{
  display:inline-flex;align-items:center;gap:8px;padding:12px 24px;border-radius:999px;
  font-family:var(--sans);font-size:14.5px;font-weight:600;letter-spacing:.5px;
  border:1px solid transparent;transition:transform .16s,box-shadow .16s,background .16s;
  cursor:pointer;
}
.btn:hover{transform:translateY(-1px)}
.btn-p{background:var(--seal);color:#fff;box-shadow:0 6px 18px -8px rgba(179,36,28,.75)}
.btn-p:hover{background:var(--seal-deep)}
.btn-g{border-color:var(--line);color:var(--ink);background:rgba(255,255,255,.6)}
.btn-g:hover{border-color:var(--ink-3);background:#fff}
.btn-d{background:transparent;border-color:rgba(255,255,255,.32);color:#f0ece2}
.btn-d:hover{background:rgba(255,255,255,.08)}

/* 卡片 */
.card{
  background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:26px;box-shadow:var(--shadow);
}
.grid{display:grid;gap:18px}
.g2{grid-template-columns:repeat(2,1fr)}
.g3{grid-template-columns:repeat(3,1fr)}
.g4{grid-template-columns:repeat(4,1fr)}
.dark .card{background:rgba(255,255,255,.045);border-color:rgba(255,255,255,.11);box-shadow:none}

/* 数字 */
.stat-row{display:grid;grid-template-columns:repeat(4,1fr);gap:1px;background:var(--line);border:1px solid var(--line);border-radius:var(--radius);overflow:hidden}
.stat{background:var(--paper-2);padding:22px 18px}
.stat b{display:block;font-family:var(--sans);font-size:26px;font-weight:700;color:var(--seal);letter-spacing:-.5px}
.stat span{font-size:13px;color:var(--ink-3);line-height:1.6;display:block;margin-top:4px}

/* 徽标卡（零件） */
.part{position:relative;background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:26px 24px;box-shadow:var(--shadow);overflow:hidden}
.part .num{font-family:var(--mono);font-size:11px;letter-spacing:2px;color:var(--ink-3)}
.part .tag{position:absolute;top:0;right:0;font-family:var(--sans);font-size:11px;letter-spacing:1.5px;padding:5px 11px;border-bottom-left-radius:9px;background:var(--indigo-tint);color:var(--indigo)}
.part h3{margin:10px 0 8px}
.part p{font-size:14.5px;color:var(--ink-2);line-height:1.8}
.part .ico{font-size:22px;margin-bottom:2px}

/* 流程 */
.flow{display:grid;grid-template-columns:repeat(4,1fr);gap:0;position:relative;margin-top:34px}
.flow .step{padding:0 18px;position:relative}
.flow .step::after{
  content:"";position:absolute;top:17px;right:-2px;width:calc(100% - 44px);
  height:1px;background:repeating-linear-gradient(90deg,var(--line) 0 6px,transparent 6px 12px);
  left:44px;
}
.flow .step:last-child::after{display:none}
.flow .dot{
  width:34px;height:34px;border-radius:50%;border:1px solid var(--seal);
  color:var(--seal);display:grid;place-items:center;font-family:var(--mono);
  font-size:13px;font-weight:700;background:var(--paper-2);position:relative;z-index:1;margin-bottom:14px;
}
.flow .step h4{margin-bottom:6px;font-size:16px}
.flow .step p{font-size:13.5px;color:var(--ink-2);line-height:1.75}

/* 引文 */
.quote{
  border-left:3px solid var(--seal);padding:6px 0 6px 22px;margin:26px 0;
  font-size:clamp(17px,2vw,21px);line-height:1.9;color:var(--ink);
}
.quote cite{display:block;font-size:13px;color:var(--ink-3);font-style:normal;margin-top:8px;font-family:var(--sans);letter-spacing:1px}

/* 表格 */
.tbl{width:100%;border-collapse:collapse;font-size:14.5px;background:var(--card)}
.tbl th,.tbl td{padding:13px 16px;text-align:left;border-bottom:1px solid var(--line-2);vertical-align:top}
.tbl th{font-family:var(--sans);font-size:12.5px;letter-spacing:1.4px;color:var(--ink-3);font-weight:600;background:rgba(0,0,0,.018);text-transform:uppercase}
.tbl tr:last-child td{border-bottom:none}
.tbl td b{color:var(--seal-deep)}
.tbl-scroll{overflow-x:auto;border:1px solid var(--line);border-radius:var(--radius)}
.dark .tbl{background:transparent}
.dark .tbl th{background:rgba(255,255,255,.05);color:#a89e8f}
.dark .tbl td{border-color:rgba(255,255,255,.09);color:#d6cec0}

/* 清单 */
.list-clean{list-style:none;display:grid;gap:11px}
.list-clean li{display:flex;gap:11px;font-size:15px;line-height:1.8;color:var(--ink-2)}
.list-clean li::before{
  content:"—";color:var(--seal);flex:none;font-weight:700;
}
.dark .list-clean li{color:#cfc7b8}

/* 子页头 */
.page-head{padding:56px 0 44px;border-bottom:1px solid var(--line);background:linear-gradient(180deg,rgba(255,255,255,.5),transparent)}
.page-head h1{font-size:clamp(28px,3.6vw,42px);margin-bottom:14px}
.crumb{font-family:var(--sans);font-size:12px;letter-spacing:1.6px;color:var(--ink-3);margin-bottom:18px}
.crumb a:hover{color:var(--seal)}

/* 页脚 */
footer{background:#191714;color:#a89e8f;padding:56px 0 30px;margin-top:0;font-family:var(--sans)}
footer .fgrid{display:grid;grid-template-columns:1.5fr 1fr 1fr 1fr;gap:34px;padding-bottom:38px;border-bottom:1px solid rgba(255,255,255,.09)}
footer h5{color:#f0ece2;font-size:13px;letter-spacing:2px;margin-bottom:14px;font-weight:700}
footer a{display:block;font-size:13.5px;line-height:2.1;color:#a89e8f}
footer a:hover{color:#e0796f}
footer .fbrand{font-family:var(--serif);font-size:22px;letter-spacing:3px;color:#f0ece2;margin-bottom:10px}
footer .fdesc{font-size:13px;line-height:1.9;max-width:34ch;color:#8c8477}
footer .fbot{padding-top:22px;display:flex;justify-content:space-between;gap:14px;flex-wrap:wrap;font-size:12px;color:#7d7466}

/* 响应式 */
@media (max-width:980px){
  .hero-grid{grid-template-columns:1fr;gap:36px}
  .g3,.g4{grid-template-columns:repeat(2,1fr)}
  .stat-row{grid-template-columns:repeat(2,1fr)}
  .flow{grid-template-columns:repeat(2,1fr);gap:26px 0}
  .flow .step:nth-child(2)::after{display:none}
  footer .fgrid{grid-template-columns:1fr 1fr}
  section.band{padding:56px 0}
}
@media (max-width:640px){
  body{font-size:16px}
  .nav-inner{padding:0 16px;gap:8px}
  .brand .bname{font-size:18px;letter-spacing:2px}
  .menu{gap:4px;padding-bottom:8px;width:100%}
  .menu a{padding:5px 10px;font-size:13px}
  .g2,.g3,.g4{grid-template-columns:1fr}
  .flow{grid-template-columns:1fr}
  .flow .step::after{display:none}
  .wrap{padding:0 18px}
  .hero{padding:40px 0 48px}
  footer .fgrid{grid-template-columns:1fr}
  .card,.part{padding:20px}
}