@import url('https://fonts.googleapis.com/css2?family=Manrope:wght@400;500;600;700;800&family=Unbounded:wght@400;500;600;700&display=swap');

:root{
  --ink:#0B1220;
  --muted:#5B6475;
  --paper:#F7F5EF;
  --line:#E6E1D5;
  --accent:#1D4ED8;
  --accent-soft:#E0EAFF;
  --orange:#C2410C;
  --green:#166534;
  --radius:24px;
  --shadow:0 26px 70px -46px rgba(11,18,32,.42);
  --shadow-sm:0 8px 24px -18px rgba(11,18,32,.28);
  --font-body:'Manrope','Segoe UI',system-ui,-apple-system,sans-serif;
  --font-display:'Unbounded','Manrope','Segoe UI',system-ui,sans-serif;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:96px}
body{
  margin:0;color:var(--ink);
  background:
    radial-gradient(circle at 8% 0%,rgba(224,234,255,.85) 0,transparent 32rem),
    radial-gradient(circle at 100% 6%,rgba(255,237,213,.8) 0,transparent 30rem),
    var(--paper);
  font-family:var(--font-body);font-size:17px;line-height:1.65;
  -webkit-font-smoothing:antialiased;
}
::selection{background:var(--accent);color:#fff}
a{color:inherit}
img,svg{max-width:100%}
button{font-family:inherit}

.read-progress{position:fixed;inset:0 0 auto 0;height:3px;z-index:200;background:rgba(11,18,32,.06)}
.read-progress span{display:block;height:100%;width:0;background:linear-gradient(90deg,var(--accent),#0EA5E9);transition:width .1s linear}

.topbar{position:sticky;top:0;z-index:100;background:rgba(247,245,239,.88);backdrop-filter:blur(16px);border-bottom:1px solid rgba(230,225,213,.8)}
.topbar-inner{width:min(1160px,calc(100% - 48px));margin:0 auto;height:72px;display:flex;align-items:center;gap:20px}
.brand{display:inline-flex;align-items:center;gap:10px;text-decoration:none;font-family:var(--font-display);font-weight:700;font-size:16px;letter-spacing:-.03em;white-space:nowrap}
.brand-mark{width:36px;height:36px;border-radius:12px;background:var(--ink);color:#fff;display:grid;place-items:center;font-size:15px;transform:rotate(-8deg)}
.brand i{color:var(--orange);font-style:normal}
.top-links{display:flex;align-items:center;gap:6px;margin-left:auto}
.top-links a{padding:9px 13px;border-radius:999px;text-decoration:none;font-size:13px;font-weight:700;color:var(--muted);transition:.2s}
.top-links a:hover{background:#fff;color:var(--ink);box-shadow:var(--shadow-sm)}
.top-links .pill-link{background:var(--ink);color:#fff}
.top-links .pill-link:hover{background:var(--accent);color:#fff}

.article-shell{width:min(1160px,calc(100% - 48px));margin:0 auto;padding:30px 0 90px}
.breadcrumbs{display:flex;flex-wrap:wrap;gap:8px;align-items:center;font-size:13px;color:var(--muted);margin-bottom:18px}
.breadcrumbs a{text-decoration:none;border-bottom:1px solid transparent}
.breadcrumbs a:hover{border-color:var(--muted)}
.breadcrumbs span{opacity:.5}

.article-hero{
  position:relative;overflow:hidden;border:1px solid rgba(230,225,213,.9);border-radius:32px;
  padding:clamp(28px,5vw,56px);
  background:linear-gradient(135deg,var(--accent-soft) 0%,#fff 72%);
  box-shadow:var(--shadow);
}
.article-hero::after{content:"";position:absolute;width:280px;height:280px;right:-90px;top:-110px;border-radius:50%;border:1px dashed var(--accent);opacity:.2}
.hero-num{position:absolute;right:34px;bottom:-26px;font-family:var(--font-display);font-size:clamp(90px,16vw,180px);line-height:1;font-weight:700;color:var(--accent);opacity:.07;pointer-events:none}
.hero-top{display:flex;flex-wrap:wrap;align-items:center;gap:14px;margin-bottom:20px}
.category{display:inline-flex;align-items:center;gap:8px;padding:7px 13px;border-radius:999px;background:var(--accent);color:#fff;font-size:11px;font-weight:800;letter-spacing:.1em;text-transform:uppercase}
.hero-icon{width:52px;height:52px;border-radius:16px;background:#fff;border:1px solid var(--line);display:grid;place-items:center;font-size:25px;box-shadow:var(--shadow-sm)}
.article-hero h1{position:relative;z-index:1;font-family:var(--font-display);font-size:clamp(30px,5.2vw,54px);line-height:1.06;letter-spacing:-.04em;margin:0 0 18px;max-width:900px}
.article-hero .lead{position:relative;z-index:1;max-width:720px;margin:0;color:#344052;font-size:clamp(16px,2vw,19px);line-height:1.65}
.article-meta{position:relative;z-index:1;display:flex;flex-wrap:wrap;gap:18px;margin-top:26px;font-size:12px;font-weight:700;color:var(--muted);text-transform:uppercase;letter-spacing:.06em}

.article-layout{display:grid;grid-template-columns:250px minmax(0,780px);gap:54px;justify-content:center;margin-top:44px;align-items:start}
.toc{position:sticky;top:94px;background:#fff;border:1px solid var(--line);border-radius:20px;padding:20px;box-shadow:var(--shadow-sm)}
.toc-title{font-size:10px;font-weight:800;letter-spacing:.14em;text-transform:uppercase;color:var(--muted);margin:0 0 12px}
.toc a{display:block;padding:8px 10px;margin:0 -6px;border-radius:9px;text-decoration:none;font-size:13px;font-weight:600;color:#465063;line-height:1.35;transition:.2s}
.toc a:hover{background:#F5F7FB;color:var(--ink)}
.toc a.is-active{background:var(--accent-soft);color:var(--accent);font-weight:800}
.toc-note{margin-top:16px;padding-top:14px;border-top:1px dashed var(--line);font-size:11px;line-height:1.5;color:var(--muted)}

.prose{min-width:0;font-size:17px;line-height:1.72;color:#263043}
.prose > p:first-child{font-size:19px;color:#1E293B}
.prose h2{font-family:var(--font-display);font-size:clamp(24px,3vw,32px);line-height:1.18;letter-spacing:-.03em;margin:52px 0 16px;color:var(--ink)}
.prose h2::before{content:"";display:block;width:40px;height:4px;border-radius:99px;background:var(--accent);margin-bottom:14px}
.prose h2:first-child{margin-top:0}
.prose h3{font-size:20px;line-height:1.3;margin:30px 0 10px;color:var(--ink)}
.prose p{margin:0 0 18px}
.prose ul,.prose ol{margin:0 0 20px;padding-left:0;list-style:none}
.prose ul li{position:relative;padding-left:22px;margin:7px 0}
.prose ul li::before{content:"";position:absolute;left:2px;top:.62em;width:7px;height:7px;border-radius:50%;background:var(--accent)}
.prose ol{counter-reset:step}
.prose ol li{position:relative;padding-left:34px;margin:10px 0;counter-increment:step}
.prose ol li::before{content:counter(step);position:absolute;left:0;top:.08em;width:23px;height:23px;border-radius:50%;background:var(--accent-soft);color:var(--accent);font-size:12px;font-weight:800;display:grid;place-items:center}
.prose strong{color:var(--ink);font-weight:800}
.prose a{color:var(--accent);text-decoration-thickness:2px;text-underline-offset:3px}
.prose h2,.prose h3{scroll-margin-top:100px}

.facts{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin:28px 0 32px}
.fact{background:#fff;border:1px solid var(--line);border-radius:18px;padding:18px 16px}
.fact small{display:block;font-size:10px;font-weight:800;letter-spacing:.09em;text-transform:uppercase;color:var(--muted);margin-bottom:7px}
.fact b{display:block;font-family:var(--font-display);font-size:20px;line-height:1.15;letter-spacing:-.03em;color:var(--ink)}
.fact span{display:block;font-size:12px;line-height:1.45;color:var(--muted);margin-top:5px}

.callout{display:grid;grid-template-columns:30px 1fr;gap:12px;margin:26px 0;padding:18px 20px;border:1px solid var(--line);border-left:4px solid var(--accent);border-radius:16px;background:#fff;font-size:15px;line-height:1.6}
.callout .ci{font-size:20px;line-height:1.3}
.callout p{margin:0}
.callout b{display:block;margin-bottom:3px;color:var(--ink)}
.callout.tip{border-left-color:#16A34A;background:#F7FDF9}
.callout.warn{border-left-color:#EA580C;background:#FFF9F2}
.callout.note{border-left-color:#0284C7;background:#F5FBFF}

.table-wrap{overflow-x:auto;margin:26px 0;border:1px solid var(--line);border-radius:18px;background:#fff;box-shadow:var(--shadow-sm)}
table{width:100%;min-width:560px;border-collapse:collapse;font-size:14px;line-height:1.45}
th,td{padding:13px 16px;text-align:left;border-bottom:1px solid var(--line);vertical-align:top}
th{background:#FAF8F2;font-size:10px;font-weight:800;letter-spacing:.08em;text-transform:uppercase;color:var(--muted);white-space:nowrap}
tr:last-child td{border-bottom:0}
td b{color:var(--ink)}

.checklist{display:grid;gap:8px;margin:22px 0}
.checklist div{position:relative;padding:12px 14px 12px 42px;background:#fff;border:1px solid var(--line);border-radius:13px;font-size:14px;line-height:1.5}
.checklist div::before{content:"✓";position:absolute;left:14px;top:11px;width:19px;height:19px;border-radius:50%;background:#DCFCE7;color:#15803D;font-size:12px;font-weight:800;display:grid;place-items:center}

.mini-quiz{margin:56px 0;padding:clamp(20px,4vw,30px);border:1px solid var(--line);border-radius:26px;background:linear-gradient(135deg,var(--accent-soft),#fff 72%)}
.mini-quiz h3{font-family:var(--font-display);font-size:22px;letter-spacing:-.03em;margin:0 0 4px}
.mini-quiz .mq-sub{font-size:13px;color:var(--muted);margin:0 0 20px}
.mq-item{padding:16px 0;border-top:1px dashed rgba(11,18,32,.15)}
.mq-item:first-of-type{border-top:0;padding-top:0}
.mq-q{font-weight:800;font-size:15px;line-height:1.45;margin:0 0 10px}
.mq-btns{display:flex;gap:8px}
.mq-btn{padding:8px 15px;border-radius:999px;border:1px solid #D8D2C6;background:#fff;font-size:12px;font-weight:800;cursor:pointer;transition:.18s}
.mq-btn:hover{border-color:var(--ink);transform:translateY(-1px)}
.mq-btn.right{background:#DCFCE7;border-color:#86EFAC;color:#166534}
.mq-btn.wrong{background:#FEE2E2;border-color:#FCA5A5;color:#991B1B}
.mq-btn.answer{border-color:#16A34A;border-style:dashed}
.mq-fb{display:none;margin-top:9px;font-size:13px;line-height:1.55;color:#475569;background:rgba(255,255,255,.75);border-radius:10px;padding:9px 12px}
.mq-fb.show{display:block}

.next-card{display:flex;align-items:center;justify-content:space-between;gap:20px;margin:54px 0 0;padding:24px 26px;border-radius:22px;background:var(--ink);color:#fff;text-decoration:none;transition:.25s;box-shadow:var(--shadow)}
.next-card:hover{transform:translateY(-3px);background:#17233A}
.next-card small{display:block;font-size:10px;font-weight:800;letter-spacing:.12em;text-transform:uppercase;color:#93A4BE;margin-bottom:5px}
.next-card b{display:block;font-family:var(--font-display);font-size:clamp(17px,2.4vw,23px);line-height:1.25;letter-spacing:-.02em}
.next-card .arrow{flex:0 0 auto;width:46px;height:46px;border-radius:50%;background:rgba(255,255,255,.1);display:grid;place-items:center;font-size:19px}

.related{margin-top:56px;padding-top:30px;border-top:1px dashed var(--line)}
.related h2{font-size:18px;margin:0 0 14px;font-family:var(--font-display);letter-spacing:-.02em}
.related-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:12px}
.related-card{display:flex;flex-direction:column;gap:6px;padding:16px;border:1px solid var(--line);border-radius:16px;background:#fff;text-decoration:none;transition:.2s}
.related-card:hover{transform:translateY(-3px);box-shadow:var(--shadow-sm);border-color:#CBD5E1}
.related-card small{font-size:10px;font-weight:800;letter-spacing:.06em;text-transform:uppercase;color:var(--accent)}
.related-card b{font-size:14px;line-height:1.35}
.related-card span{font-size:11px;color:var(--muted)}

.back-course{display:inline-flex;align-items:center;gap:8px;margin-top:34px;padding:11px 17px;border-radius:999px;background:#fff;border:1px solid var(--line);text-decoration:none;font-size:13px;font-weight:800;transition:.2s}
.back-course:hover{border-color:var(--ink);transform:translateY(-2px)}

.site-footer{margin-top:80px;border-top:1px solid var(--line);padding:36px 0 54px}
.footer-inner{width:min(1160px,calc(100% - 48px));margin:0 auto;display:flex;justify-content:space-between;align-items:flex-start;gap:28px;flex-wrap:wrap}
.footer-brand{max-width:340px}
.footer-brand p{margin:10px 0 0;font-size:13px;color:var(--muted);line-height:1.6}
.footer-links{display:flex;flex-wrap:wrap;gap:10px 18px;font-size:13px;font-weight:700}
.footer-links a{text-decoration:none;color:#475569}
.footer-links a:hover{color:var(--accent)}
.footer-bottom{width:min(1160px,calc(100% - 48px));margin:26px auto 0;padding-top:18px;border-top:1px dashed var(--line);font-size:11px;color:var(--muted);line-height:1.6}

@media(max-width:980px){
  .article-layout{grid-template-columns:1fr;gap:24px}
  .toc{position:static;display:grid;grid-template-columns:1fr 1fr;gap:2px 8px}
  .toc-title,.toc-note{grid-column:1/-1}
  .related-grid{grid-template-columns:1fr 1fr}
}
@media(max-width:700px){
  body{font-size:16px}
  .topbar-inner{width:calc(100% - 28px);height:64px}
  .top-links a:not(.pill-link){display:none}
  .article-shell{width:calc(100% - 28px);padding-top:18px}
  .article-hero{border-radius:24px;padding:24px 20px}
  .article-layout{margin-top:28px}
  .toc{grid-template-columns:1fr}
  .facts{grid-template-columns:1fr}
  .mini-quiz{border-radius:20px}
  .related-grid{grid-template-columns:1fr}
  .next-card{padding:20px;border-radius:18px}
  .next-card .arrow{width:38px;height:38px}
  .footer-inner,.footer-bottom{width:calc(100% - 28px)}
}
@media(prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{transition:none!important;animation:none!important}
}