:root{--bg:#F5FBFF;--white:#fff;--soft:#EAF7FC;--pale:#DFF5FB;--aqua:#25C8D1;--sky:#25B6E8;--blue:#1787DB;--deep:#174B78;--heading:#173B60;--text:#2D4359;--muted:#687F93;--line:#DCEBF3;--footer:#123653;--shadow:0 12px 35px rgba(23,75,120,.07)}
*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:90px}body{margin:0;background:var(--bg);color:var(--text);font-family:Arial,'PingFang SC','Microsoft YaHei',sans-serif;font-size:16px;line-height:1.8}body.drawer-open{overflow:hidden}a{color:var(--deep);text-underline-offset:4px}a:hover{color:var(--blue)}button{font:inherit;cursor:pointer}img{max-width:100%}.container{width:min(100% - 48px,1160px);margin-inline:auto}.skip-link{position:absolute;top:-80px;left:10px;background:#fff;padding:8px 16px;z-index:200}.skip-link:focus{top:10px}.site-header{background:#fff;border-bottom:1px solid var(--line);position:sticky;top:0;z-index:40;box-shadow:0 3px 18px rgba(12,64,115,.04)}.header-inner{height:72px;display:flex;align-items:center;gap:22px}.brand{display:inline-flex;flex:none;align-items:center;text-decoration:none;min-width:0}.brand-logo{width:auto;height:auto;max-height:38px;max-width:178px;object-fit:contain}.brand-text{display:flex;align-items:center;gap:9px;font-weight:800;font-size:21px;color:var(--deep);line-height:1.12;white-space:nowrap}.brand-mark{display:grid;place-items:center;background:linear-gradient(135deg,var(--aqua),var(--blue));color:#fff;width:37px;height:37px;border-radius:10px;font-size:25px}.brand-text small{display:block;letter-spacing:1.25px;font-size:9px;color:var(--blue);margin-top:3px}.desktop-nav{display:flex;align-items:center;gap:clamp(9px,1.5vw,23px);margin-left:auto}.desktop-nav a{font-size:14px;text-decoration:none;white-space:nowrap;color:var(--deep);font-weight:600;padding-block:23px;position:relative}.desktop-nav a.active,.desktop-nav a:hover{color:var(--blue)}.desktop-nav a.active:after{content:"";height:3px;position:absolute;bottom:0;left:0;right:0;background:var(--aqua);border-radius:4px}.main-btn{display:inline-flex;align-items:center;justify-content:center;min-width:82px;height:42px;padding:0 20px;border-radius:999px;background:linear-gradient(110deg,#25C8D1,#25B6E8,#1787DB);color:white;font-weight:700;text-decoration:none;white-space:nowrap;box-shadow:0 7px 18px rgba(37,182,232,.18);font-size:14px}.main-btn:hover{color:white;filter:brightness(.96)}.header-entry{margin-left:3px}.menu-toggle{display:none;border:0;background:transparent;width:42px;height:42px;padding:10px;flex-direction:column;justify-content:center;gap:5px}.menu-toggle span{height:2px;background:var(--deep);width:100%;border-radius:2px}.drawer-overlay{visibility:hidden;opacity:0;pointer-events:none;position:fixed;inset:0;background:rgba(9,35,57,.5);z-index:70;transition:opacity .2s,visibility .2s}.mobile-drawer{position:fixed;left:0;top:0;bottom:0;width:min(86vw,340px);overflow-y:auto;background:white;z-index:80;transform:translateX(-105%);transition:transform .23s ease;box-shadow:8px 0 30px rgba(0,0,0,.14);padding:20px 22px}.drawer-open .drawer-overlay{visibility:visible;opacity:1;pointer-events:auto}.drawer-open .mobile-drawer{transform:translateX(0)}.drawer-heading{display:flex;align-items:center;justify-content:space-between;gap:6px;padding-bottom:15px;border-bottom:1px solid var(--line)}.drawer-close{border:0;background:var(--soft);color:var(--deep);font-size:28px;line-height:1;width:38px;height:38px;border-radius:10px}.drawer-group{display:grid;gap:1px;border-bottom:1px solid var(--line);padding:13px 0}.drawer-group b{font-size:13px;color:var(--blue);letter-spacing:.05em}.drawer-group a{text-decoration:none;padding:6px 8px;border-radius:8px;font-size:15px}.drawer-group a:hover{background:var(--soft)}main{min-height:60vh}.hero{padding:50px 0 34px}.hero-panel{background:linear-gradient(120deg,#fff,#EAF7FC);border:1px solid var(--line);border-radius:24px;padding:clamp(22px,4.3vw,52px);display:grid;grid-template-columns:1.05fr .95fr;align-items:center;gap:28px;box-shadow:var(--shadow)}.eyebrow{color:#107ea7;font-size:13px;font-weight:800;letter-spacing:.12em;text-transform:uppercase;margin:0 0 13px}.hero h1{font-size:clamp(27px,3.4vw,40px);line-height:1.35;color:var(--heading);margin:0 0 18px;letter-spacing:-.02em}.hero p,.intro{font-size:16px;line-height:1.85}.hero-actions{display:flex;gap:12px;flex-wrap:wrap;margin-top:24px}.outline-btn{display:inline-flex;align-items:center;justify-content:center;border:1px solid #A9D9E8;border-radius:999px;padding:9px 20px;text-decoration:none;font-weight:700;background:#fff}.media{width:100%;display:flex;justify-content:center;align-items:center;overflow:hidden;background:var(--soft);border-radius:14px;min-height:180px}.media img{display:block;width:auto;height:auto;max-height:100%;max-width:100%;object-fit:contain;object-position:center}.media-fallback{flex-direction:column;color:#4E8CAB;gap:6px;text-align:center;padding:20px;font-size:14px;font-weight:600;border:1px dashed #B3DFEC}.fallback-symbol{font-size:48px;line-height:1;color:#62BED9;font-weight:300}.hero-media{height:310px}.feature-media{height:240px}.card-media{height:170px}.phone-media{height:330px}.wide-media{height:220px}.section{padding:32px 0}.section-heading{display:flex;align-items:end;gap:18px;justify-content:space-between;margin-bottom:24px}.section h2,.section-heading h2,.related h2{font-size:26px;color:var(--heading);line-height:1.4;margin:0 0 10px}.section-heading p{margin:0;color:var(--muted);max-width:660px}.tiny-link{font-size:14px;font-weight:700;white-space:nowrap}.grid-3{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:20px}.grid-2{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:20px}.topic-card,.reading-card,.info-panel,.article-box{background:#fff;border:1px solid var(--line);border-radius:16px;box-shadow:var(--shadow)}.topic-card{padding:24px;display:flex;flex-direction:column;gap:8px;text-decoration:none;transition:transform .2s,border-color .2s}.topic-card:hover{transform:translateY(-3px);border-color:#88D9E8}.topic-card .number{color:#1EADD2;letter-spacing:.14em;font-size:12px;font-weight:800}.topic-card h3,.reading-card h3{font-size:19px;color:var(--heading);margin:0;line-height:1.45}.topic-card p,.reading-card p{font-size:15px;line-height:1.8;margin:0;color:var(--text)}.topic-card .read-more{margin-top:auto;color:var(--blue);font-weight:700;font-size:13px}.reading-card{padding:24px}.reading-card h3{margin:10px 0}.reading-card .mini-label{font-size:12px;color:var(--blue);font-weight:800}.split{display:grid;grid-template-columns:1fr 1fr;align-items:center;gap:30px}.strip{background:#EAF7FC;border-block:1px solid #D0EAF2;margin-top:30px}.bullet-links{padding:0;list-style:none;margin:10px 0}.bullet-links li{padding:8px 0;border-bottom:1px solid var(--line)}.bullet-links a{text-decoration:none;font-weight:600}.page-head{padding:53px 0 32px;background:linear-gradient(125deg,#E8FAFD 0%,#F5FBFF 72%);border-bottom:1px solid var(--line)}.page-head .container{max-width:1160px}.page-head h1{font-size:clamp(24px,3.2vw,34px);line-height:1.4;color:var(--heading);margin:0 0 13px}.page-head p{max-width:780px;margin:0;color:var(--text);font-size:16px}.crumb{font-size:13px;color:var(--muted);margin-bottom:14px}.crumb a{color:var(--deep)}.article-layout{display:grid;grid-template-columns:minmax(0,820px) minmax(210px,1fr);gap:42px;align-items:start;padding-top:38px}.prose{max-width:820px}.prose h2{font-size:24px;color:var(--heading);line-height:1.45;margin:38px 0 14px}.prose h3{font-size:19px;color:var(--heading);line-height:1.5;margin:26px 0 9px}.prose p{margin:0 0 17px}.prose ul,.prose ol{padding-left:25px;margin:0 0 19px}.prose li{margin-bottom:9px}.prose .lead{font-size:17px;color:#214C6D}.toc{background:white;border:1px solid var(--line);padding:22px;border-radius:16px;position:sticky;top:95px}.toc h2{font-size:17px;margin:0 0 10px;color:var(--heading)}.toc a{display:block;text-decoration:none;padding:8px 0;font-size:14px;border-bottom:1px solid var(--line)}.callout{background:#EAF7FC;border-left:4px solid var(--aqua);padding:18px 22px;border-radius:0 12px 12px 0;margin:25px 0}.comparison{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin:22px 0}.comparison>div{background:white;border:1px solid var(--line);padding:20px;border-radius:14px}.comparison h3{margin-top:0}.table-wrap{overflow-x:auto;margin:20px 0}.data-table{border-collapse:collapse;width:100%;min-width:550px;background:#fff;font-size:15px}.data-table th,.data-table td{border:1px solid var(--line);padding:12px 14px;text-align:left;vertical-align:top}.data-table th{background:var(--soft);color:var(--heading)}.timeline{border-left:3px solid #A6E0E9;padding-left:22px;margin:25px 0}.timeline article{margin:0 0 25px;position:relative}.timeline article:before{content:"";position:absolute;left:-30px;top:9px;width:12px;height:12px;border-radius:50%;background:var(--aqua);border:3px solid var(--bg)}.timeline h3{margin:0 0 5px}.quote-card{font-size:21px;line-height:1.6;font-weight:700;color:var(--deep);background:white;border:1px solid var(--line);border-radius:16px;padding:28px;margin:26px 0}.related{padding:40px 0 55px}.related-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}.related-grid a{padding:15px 18px;text-decoration:none;font-weight:700;background:white;border:1px solid var(--line);border-radius:10px;display:flex;justify-content:space-between;gap:15px}.visual-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:24px}.visual-tile{background:#fff;border:1px solid var(--line);border-radius:18px;padding:18px}.visual-tile h3{margin:14px 2px 4px;color:var(--heading);font-size:19px}.visual-tile p{margin:0 2px 4px;font-size:15px}.faq details{border-bottom:1px solid var(--line);padding:14px 0}.faq summary{font-size:17px;cursor:pointer;font-weight:700;color:var(--heading)}.faq details p{margin:10px 0}.site-footer{background:var(--footer);color:#EAF7FF;margin-top:30px;padding:42px 0 18px}.footer-inner{display:grid;grid-template-columns:2fr 1fr;gap:60px}.footer-brand .brand-text{color:#fff}.footer-brand .brand-text small{color:#A9E4F3}.site-footer p{max-width:540px;font-size:14px;color:#D7E9F4}.site-footer .fine-print{color:#B7D0DF}.site-footer nav{display:flex;flex-wrap:wrap;align-content:start;gap:8px 20px}.site-footer nav h2{font-size:17px;width:100%;margin:0 0 8px}.site-footer a{color:#EAF7FF}.site-footer nav a{font-size:14px;text-decoration:none}.footer-bottom{border-top:1px solid rgba(255,255,255,.16);margin-top:26px;padding-top:15px;display:flex;justify-content:space-between;font-size:13px;color:#B8D4E5}.mobile-bottom{display:none}.to-top{position:fixed;right:18px;bottom:22px;width:42px;height:42px;border:0;border-radius:50%;background:var(--deep);color:white;box-shadow:var(--shadow);opacity:0;visibility:hidden;transition:opacity .15s,visibility .15s;z-index:30}.to-top.show{opacity:1;visibility:visible}
@media(max-width:1100px){.desktop-nav{gap:10px}.desktop-nav a{font-size:13px}.brand-logo{max-width:142px}.brand-text{font-size:18px}.brand-mark{width:32px;height:32px}}
@media(max-width:980px){.desktop-nav{display:none}.menu-toggle{display:flex}.header-inner{justify-content:space-between;height:60px;gap:10px}.brand{margin:auto}.header-entry{margin:0;padding:0 13px;height:39px;min-width:79px}.brand-logo{max-height:30px;max-width:145px}.brand-text{font-size:17px}.brand-mark{width:30px;height:30px;font-size:20px}.container{width:calc(100% - 40px)}.article-layout{grid-template-columns:1fr;gap:12px}.toc{position:static;order:-1}.toc a{display:inline-block;margin-right:22px}.hero{padding-top:28px}}
@media(max-width:700px){.container{width:calc(100% - 32px)}body{font-size:15px}.hero-panel{grid-template-columns:1fr;padding:22px;gap:18px}.hero-panel .media{order:-1}.hero-media{height:205px}.hero h1{font-size:29px}.hero p,.intro{font-size:15px}.grid-3,.grid-2,.split,.visual-grid,.comparison{grid-template-columns:1fr}.section{padding:25px 0}.section h2,.section-heading h2{font-size:22px}.section-heading{align-items:start;gap:10px}.section-heading p{font-size:14px}.topic-card{padding:20px}.page-head{padding:30px 0 25px}.page-head h1{font-size:27px}.page-head p{font-size:15px}.prose h2{font-size:21px}.prose h3{font-size:18px}.prose .lead{font-size:16px}.article-layout{padding-top:24px}.related-grid{grid-template-columns:1fr}.related{padding:24px 0 35px}.feature-media{height:185px}.card-media{height:155px}.wide-media{height:175px}.phone-media{height:295px}.footer-inner{grid-template-columns:1fr;gap:22px}.footer-bottom{gap:12px;flex-wrap:wrap}.site-footer{padding-bottom:84px}.mobile-bottom{position:fixed;bottom:0;left:0;right:0;display:grid;grid-template-columns:repeat(4,1fr);background:#fff;border-top:1px solid var(--line);z-index:35;padding-bottom:env(safe-area-inset-bottom)}.mobile-bottom a{padding:10px 2px;text-align:center;text-decoration:none;font-size:13px;font-weight:700;color:var(--deep)}.mobile-bottom a[aria-current]{color:var(--blue);background:#EFFAFF}.to-top{bottom:75px}.section-heading{flex-wrap:wrap}.hero-actions .main-btn,.hero-actions .outline-btn{padding-inline:14px}}
@media(max-width:350px){.header-inner{gap:4px}.brand-text{font-size:14px}.brand-mark{width:25px;height:25px}.header-entry{font-size:12px;min-width:70px;padding:0 9px}.menu-toggle{width:36px;padding:8px}.hero h1{font-size:27px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*:before,*:after{transition:none!important;animation:none!important}}