:root{--bg:#f6fafc;--white:#fff;--mist:#eaf6fa;--mist2:#edf4f8;--cyan:#25c8d1;--sky:#25b6e8;--blue:#1787db;--deep:#174b78;--title:#183a56;--body:#31485d;--muted:#687d8e;--line:#dce9f0;--footer:#123653;--radius:16px}*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:125px}body{margin:0;overflow-x:hidden;background:var(--bg);color:var(--body);font:16px/1.8 Arial,"PingFang SC","Microsoft YaHei",sans-serif}a{color:var(--deep);text-underline-offset:4px}a:hover{color:#086baf}a:focus-visible,button:focus-visible,summary:focus-visible{outline:3px solid #1787db;outline-offset:3px}button{font:inherit;cursor:pointer}.container{width:min(100% - 56px,1180px);margin:auto}h1,h2,h3{color:var(--title);line-height:1.38;letter-spacing:-.02em}h1{font-size:clamp(32px,3vw,36px);margin:0 0 18px}h2{font-size:26px;margin:0 0 21px}h3{font-size:20px;margin:0 0 12px}p{margin:0 0 16px}section{scroll-margin-top:130px}.eyebrow{color:#167ba0;font-weight:700;font-size:13px;letter-spacing:.12em;text-transform:uppercase}.lead{font-size:17px;line-height:1.85;color:#435e73}.muted{color:var(--muted)}.site-header{background:#fff;border-bottom:1px solid var(--line);position:relative;z-index:25}.topbar{height:72px;display:flex;align-items:center;gap:24px}.brand{display:flex;align-items:center;text-decoration:none;max-width:280px;flex-shrink:0}.brand-text{font-size:23px;letter-spacing:.035em;color:var(--deep);font-weight:900;white-space:nowrap}.brand-text strong{color:#13a9b9}.topbar-note{color:var(--muted);margin:auto;font-size:14px}.entry-btn{background:#174b78;color:white;border-radius:9px;padding:9px 22px;white-space:nowrap;font-weight:700;text-decoration:none;line-height:26px}.entry-btn:hover{color:white;background:#116b9b}.desktop-nav{background:var(--deep)}.nav-row{display:flex;gap:24px;justify-content:space-between;align-items:center;min-height:48px}.nav-row a{color:#eaf7ff;text-decoration:none;font-size:15px;white-space:nowrap;border-bottom:3px solid transparent;padding:9px 1px 7px}.nav-row a:hover,.nav-row a[aria-current]{color:white;border-bottom-color:var(--cyan);font-weight:700}.menu-toggle{display:none}.drawer-shade{position:fixed;inset:0;background:#132c45a6;visibility:hidden;pointer-events:none;z-index:39}.drawer-shade[hidden]{display:none}.mobile-drawer{position:fixed;inset:0 auto 0 0;width:min(86vw,344px);background:#fff;z-index:40;transform:translateX(-101%);visibility:hidden;pointer-events:none;overflow-y:auto;padding:22px}.drawer-open{overflow:hidden}.drawer-open .drawer-shade{visibility:visible;pointer-events:auto}.drawer-open .mobile-drawer{transform:translateX(0);visibility:visible;pointer-events:auto}.drawer-head{display:flex;justify-content:space-between;align-items:center;color:var(--deep);border-bottom:1px solid var(--line);padding-bottom:18px}.drawer-close{background:none;border:0;font-size:32px;line-height:1}.drawer-group{margin:22px 0}.drawer-group h2{font-size:14px;color:var(--muted);margin-bottom:8px}.drawer-group a{display:block;padding:9px 3px;text-decoration:none;border-bottom:1px solid var(--line)}.skip-link{position:absolute;left:-999px;top:4px;background:white;padding:8px;z-index:100}.skip-link:focus{left:12px}.section{padding:54px 0}.section--alt{background:var(--mist2)}.section-heading{display:flex;justify-content:space-between;gap:20px;align-items:end;margin-bottom:22px}.section-heading p{max-width:570px}.hero{padding:44px 0 48px}.hero-grid{display:grid;grid-template-columns:56fr 44fr;gap:36px;align-items:center}.hero h1{font-size:clamp(38px,3.7vw,42px)}.hero p{max-width:650px}.cta-row{display:flex;gap:13px;flex-wrap:wrap;margin-top:26px}.btn{display:inline-block;background:var(--deep);color:white;text-decoration:none;border-radius:9px;padding:10px 20px;font-weight:700}.btn:hover{background:#096fab;color:white}.btn--light{background:#e0f3fa;color:var(--deep)}.quickbar{background:#eaf6fa;border-top:1px solid var(--line);border-bottom:1px solid var(--line)}.quickbar-inner{display:grid;grid-template-columns:repeat(3,1fr);gap:20px;padding:14px 0}.quickbar p{margin:0;font-size:13px}.quickbar strong{color:var(--title);margin-right:8px}.quickbar a{margin-right:12px;white-space:nowrap}.topic-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:14px}.topic-card{background:white;border:1px solid var(--line);padding:22px;border-radius:var(--radius);text-decoration:none;min-width:0;transition:border-color .2s}.topic-card:hover{border-color:#25b6e8}.topic-card b{display:block;color:var(--title);font-size:18px;margin-bottom:8px}.topic-card p{font-size:14px;line-height:1.75;margin:0;color:var(--body)}.topic-card span{font-size:13px;color:#0877a0}.editor-grid{display:grid;grid-template-columns:2fr 1fr;gap:20px}.feature-article,.mini-article,.info-card{background:white;border:1px solid var(--line);border-radius:var(--radius);padding:26px}.feature-article{background:linear-gradient(135deg,#fff 70%,#eaf6fa)}.mini-stack{display:grid;gap:16px}.mini-article h3{margin-top:0}.mini-article p,.feature-article p{line-height:1.8}.text-link{display:inline-block;font-weight:700;color:#1168a2;text-decoration-thickness:1px}.split{display:grid;grid-template-columns:1fr 1fr;gap:38px;align-items:center}.split--reverse .media{order:-1}.rule-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:18px}.steps{display:grid;grid-template-columns:repeat(4,1fr);gap:12px;counter-reset:steps}.step{border-top:3px solid #25c8d1;background:#fff;padding:19px;border-radius:0 0 12px 12px}.step b{display:block;color:var(--title)}.step-number{color:#087aa5;font-weight:800;font-size:13px}.editor-note{border-left:4px solid var(--cyan);background:#edf7fa;padding:20px 24px}.page-intro{padding:45px 0 28px}.page-intro p{max-width:810px}.article-main{max-width:780px}.article-section{margin:0 0 44px}.article-section p{line-height:1.83}.article-section h2{margin-bottom:17px}.article-section h3{margin-top:25px}.page-body{padding:16px 0 55px}.wide-panel{background:white;border:1px solid var(--line);border-radius:var(--radius);padding:28px;margin:22px 0 42px}.tinted{background:var(--mist)}.reading-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:16px}.reading-card{padding:21px;background:#fff;border:1px solid var(--line);border-radius:12px}.reading-card b{color:var(--title)}.reading-card p{font-size:15px;margin-top:10px}.table-wrap{overflow-x:auto;margin:25px 0 35px;border:1px solid var(--line);border-radius:12px}table{border-collapse:collapse;width:100%;min-width:560px;background:#fff;font-size:15px}caption{font-weight:bold;text-align:left;padding:12px}th,td{text-align:left;vertical-align:top;padding:14px 17px;border-bottom:1px solid var(--line)}th{background:#eaf6fa;color:var(--title);white-space:nowrap}tr:last-child td{border-bottom:0}.article-with-aside{display:grid;grid-template-columns:minmax(0,760px) minmax(0,240px);gap:46px;align-items:start}.side-index{border-top:4px solid var(--cyan);background:white;padding:18px;position:sticky;top:20px;border-radius:0 0 12px 12px}.side-index h2{font-size:18px}.side-index ul{padding-left:17px;margin:0}.side-index li{margin:9px 0;font-size:14px}.media{display:flex;justify-content:center;align-items:center;width:100%;min-width:0;overflow:hidden;border-radius:14px;background:#eaf6fa;position:relative}.media img{display:block;width:auto;height:auto;max-width:100%;max-height:100%;object-fit:contain;object-position:center}.media--logo{height:38px;max-width:260px;background:transparent;justify-content:flex-start;border-radius:0}.media--hero{height:clamp(250px,26vw,330px)}.media--feature{height:250px}.media--card{height:170px}.media--banner{height:220px}.media--mobile{height:350px;max-width:320px}.media.portrait{max-width:340px;margin-inline:auto}.media.ultra-wide{height:160px}.media--missing{background:linear-gradient(145deg,#e5f4f8,#eff9fb);border:1px solid #dce9f0}.media--missing::after{content:"";width:36%;height:1px;background:#c6e0e8;transform:rotate(-20deg)}.gallery-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:20px}.gallery-card{background:#fff;border:1px solid var(--line);padding:15px;border-radius:14px}.gallery-card figcaption{padding:15px 4px 5px}.gallery-card h3{margin-bottom:7px}.gallery-card p{margin-bottom:0;font-size:15px}.anchor-links{display:flex;gap:12px;flex-wrap:wrap;margin:20px 0}.anchor-links a{padding:7px 13px;border:1px solid #bedeea;background:white;border-radius:8px;text-decoration:none;font-size:14px}.related{margin:52px 0 22px;padding-top:24px;border-top:1px solid var(--line)}.related-list{display:flex;gap:12px;flex-wrap:wrap}.related-list a{background:white;border:1px solid var(--line);padding:12px 17px;border-radius:9px;text-decoration:none}.faq details{background:#fff;border:1px solid var(--line);border-radius:10px;padding:15px 19px;margin-bottom:10px}.faq summary{font-weight:700;color:var(--title);cursor:pointer}.faq details p{margin:13px 0 0}.service-table td:first-child{white-space:nowrap;font-weight:700}.site-footer{background:var(--footer);color:#eaf7ff;padding:42px 0 18px}.footer-layout{display:grid;grid-template-columns:1.2fr 1fr;gap:60px}.footer-brand{color:white;text-decoration:none;font-weight:800;font-size:21px}.footer-brand small{display:block;font-size:12px;letter-spacing:.12em}.footer-note{font-size:13px;color:#c4e0ef;max-width:650px}.site-footer nav{display:grid;grid-template-columns:1fr 1fr;gap:9px 20px;align-content:start}.site-footer nav a{color:#eaf7ff;font-size:14px}.footer-bottom{border-top:1px solid #ffffff32;margin-top:24px;padding-top:12px;color:#c4e0ef;font-size:13px}.bottom-nav{display:none}.back-top{position:fixed;right:24px;bottom:25px;width:44px;height:44px;border:0;border-radius:50%;background:var(--deep);color:#fff;opacity:0;pointer-events:none;z-index:15}.back-top.visible{opacity:1;pointer-events:auto}.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap}
@media(max-width:980px){.container{width:min(100% - 44px,1180px)}.desktop-nav{display:none}.topbar{height:64px;justify-content:space-between;gap:12px}.menu-toggle{display:flex;flex-direction:column;align-items:center;justify-content:center;gap:5px;width:40px;height:40px;flex:none;border:0;background:transparent}.menu-toggle span{width:21px;height:2px;background:var(--deep)}.brand{margin:auto}.topbar-note{display:none}.entry-btn{height:40px;padding:7px 13px;font-size:14px}.media--logo{height:30px;max-width:200px}.brand-text{font-size:19px}.hero-grid{gap:20px}.topic-grid{grid-template-columns:repeat(2,1fr)}.article-with-aside{grid-template-columns:minmax(0,1fr)}.side-index{position:static}.quickbar-inner{grid-template-columns:1fr;gap:7px}.drawer-shade,.mobile-drawer{transition:opacity .2s,transform .2s,visibility .2s}}
@media(max-width:760px){.container{width:min(100% - 32px,1180px)}.hero-grid,.editor-grid,.split,.footer-layout{grid-template-columns:1fr}.hero{padding-top:24px}.hero .media{order:-1}.split--reverse .media{order:initial}.section{padding:34px 0}.reading-grid,.rule-grid{grid-template-columns:1fr 1fr}.steps{grid-template-columns:1fr 1fr}.feature-article,.mini-article{padding:20px}.page-intro{padding-top:28px}.bottom-nav{display:grid;grid-template-columns:repeat(4,1fr);position:fixed;left:0;right:0;bottom:0;background:white;border-top:1px solid var(--line);z-index:24;padding-bottom:env(safe-area-inset-bottom)}.bottom-nav a{padding:9px 2px;text-align:center;text-decoration:none;font-size:13px}.bottom-nav a[aria-current]{font-weight:800;color:#0078a8}body{padding-bottom:calc(50px + env(safe-area-inset-bottom))}.site-footer{padding-bottom:30px}.back-top{bottom:75px;right:14px}}
@media(max-width:640px){h1{font-size:27px}.hero h1{font-size:29px}h2{font-size:22px}h3{font-size:18px}body{font-size:15px}.lead{font-size:16px}.media--hero{height:200px}.media--feature{height:180px}.media--card{height:145px}.media--banner{height:150px}.media--mobile{height:290px;max-width:250px}.media.ultra-wide{height:100px}.topic-grid,.rule-grid,.reading-grid,.gallery-grid{grid-template-columns:1fr}.topic-card{padding:18px}.wide-panel{padding:19px}.section-heading{display:block}.brand-text{font-size:16px}.entry-btn{font-size:13px;padding:7px 11px}.steps{grid-template-columns:1fr}.quickbar-inner{display:flex;overflow-x:auto;gap:12px}.quickbar p{flex-shrink:0}.footer-layout{gap:20px}.footer-layout nav{grid-template-columns:1fr 1fr}.topbar{gap:5px}}
@media(max-height:470px) and (max-width:760px){.bottom-nav{position:static}body{padding-bottom:0}.back-top{bottom:20px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*::before,*::after{animation:none!important;transition:none!important}}