*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:20px}body{margin:0;background:#F4F7FA;color:#344C60;font:16px/1.8 Arial,"PingFang SC","Microsoft YaHei",sans-serif;overflow-wrap:break-word}body.menu-open{overflow:hidden}img{max-width:100%;height:auto}a{color:#176db6;text-decoration:none}a:hover{text-decoration:underline}a:focus-visible,button:focus-visible,summary:focus-visible{outline:3px solid #13B8C5;outline-offset:3px}button{font:inherit;cursor:pointer}.shell{width:min(1200px,calc(100% - 56px));margin-inline:auto}.reading{max-width:800px}h1,h2,h3{color:#18364B;line-height:1.38;margin-top:0}h1{font-size:clamp(32px,3vw,42px);letter-spacing:-.035em}h2{font-size:26px;margin-bottom:18px}h3{font-size:20px;margin-bottom:12px}p{margin:0 0 18px}section{margin-block:54px}ul,ol{padding-left:1.4em}li{margin:0 0 9px}.eyebrow{display:block;color:#168796;letter-spacing:.09em;font-size:13px;font-weight:700;margin-bottom:10px}.lead{font-size:17px;color:#465f72}.muted{color:#64798A}.pill-link,.solid-link{display:inline-flex;align-items:center;min-height:44px;padding:8px 20px;border-radius:8px;background:#102E46;color:#fff;font-weight:700}.pill-link:hover,.solid-link:hover{background:#237BD3;color:#fff;text-decoration:none}.text-link{font-weight:700}.site-header{background:white;position:relative;z-index:20;border-bottom:1px solid #DCE6ED}.brand-row{height:72px;display:flex;align-items:center;gap:24px}.brand{display:inline-flex;align-items:center;flex-shrink:0;color:#102E46;text-decoration:none}.brand img{display:block;width:auto;height:auto;max-height:38px;max-width:min(240px,36vw);object-fit:contain}.brand-text{font-size:24px;font-weight:800;white-space:nowrap;line-height:1.1}.brand-text small,.footer-brand small{display:block;font-size:10px;letter-spacing:.19em;margin-top:5px}.brand-note{font-size:13px;color:#64798A;flex:1}.entry-button{margin-left:auto;flex-shrink:0;min-height:42px;display:inline-flex;align-items:center;padding:8px 18px;border-radius:8px;background:#13B8C5;color:#062e40;font-weight:750}.entry-button:hover{background:#0e9ca9;text-decoration:none}.desktop-nav{background:#102E46}.nav-layout{height:50px;display:flex;align-items:stretch;justify-content:space-between;gap:5px}.desktop-nav a{color:#e9f3f8;padding:12px 14px;font-size:14px;font-weight:600;white-space:nowrap;position:relative}.desktop-nav a:hover{background:#163C57;text-decoration:none}.desktop-nav a[aria-current="page"]{font-weight:800;background:#163C57}.desktop-nav a[aria-current="page"]:after{content:"";position:absolute;left:14px;right:14px;bottom:0;background:#13B8C5;height:3px}.menu-toggle{display:none}.drawer-overlay,.mobile-drawer{display:none}.no-js-nav{display:flex;gap:14px;flex-wrap:wrap;padding-block:14px}.skip-link{position:absolute;top:-100px;left:12px;z-index:999;background:#fff;padding:10px}.skip-link:focus{top:12px}.breadcrumbs{font-size:13px;margin:25px 0 22px;display:flex;gap:12px;align-items:center;color:#64798A}.page-header{padding:36px 0 8px}.page-header h1{font-size:35px;max-width:980px;margin-bottom:14px}.page-header .lead{max-width:850px}.cover{display:grid;grid-template-columns:52fr 48fr;align-items:center;gap:36px;padding-block:54px 12px;margin:0}.cover p{max-width:590px}.cover-actions{display:flex;gap:14px;flex-wrap:wrap;margin-top:25px}.media-frame{display:flex;align-items:center;justify-content:center;min-width:0;width:100%;padding:9px;border-radius:14px;background:#EAF1F6;margin:0}.media-frame img{display:block;width:auto;height:auto;max-width:100%;max-height:var(--media-limit,220px);object-fit:contain;object-position:center}.media-frame--hero{--media-limit:310px}.media-frame--feature{--media-limit:250px}.media-frame--card{--media-limit:185px}.media-frame--banner{--media-limit:210px}.media-frame--mobile{--media-limit:350px;max-width:320px;margin-inline:auto}.media-fallback{min-height:115px;min-width:0;width:100%;display:grid;place-items:center;border:1px dashed #abc2cf;border-radius:8px;color:#64798A;font-size:13px;background:#f6fafc}.media-frame--hero .media-fallback{min-height:200px}.section-header{display:flex;justify-content:space-between;align-items:baseline;gap:16px;margin-bottom:23px;border-bottom:1px solid #DCE6ED;padding-bottom:11px}.section-header h2{margin:0}.topic-directory{display:grid;grid-template-columns:1fr 1fr;gap:0 35px}.topic-row{display:grid;grid-template-columns:40px 1fr;gap:12px;padding:22px 0;border-bottom:1px solid #DCE6ED}.topic-number{font-size:14px;font-weight:800;color:#13a3ae}.topic-row h3{margin:0 0 6px}.topic-row p{font-size:15px;margin-bottom:8px}.editor-grid{display:grid;grid-template-columns:2fr 1fr;gap:30px}.feature-story{background:white;padding:30px;border:1px solid #DCE6ED;border-radius:12px}.feature-story .label{font-size:13px;color:#168796;font-weight:700}.feature-story h3{font-size:24px;margin-top:10px}.story-side article{padding:14px 0 19px;border-bottom:1px solid #DCE6ED}.story-side article:first-child{padding-top:0}.story-side h3{font-size:19px}.split{display:grid;grid-template-columns:1fr 1fr;gap:35px;align-items:center}.split.wide-image{grid-template-columns:1.08fr .92fr}.soft-section{padding:32px;background:#EAF1F6;border-radius:14px}.note-band{background:#102E46;color:#E9F2F7;padding:30px 32px;border-radius:12px}.note-band h2,.note-band h3{color:#fff}.rule-cards{display:grid;grid-template-columns:repeat(3,1fr);gap:17px}.rule-cards article{padding:24px;background:#fff;border:1px solid #DCE6ED;border-top:3px solid #13B8C5;border-radius:10px}.rule-cards article:nth-child(2){margin-top:22px}.rule-cards article:nth-child(3){margin-top:44px}.route-steps{display:grid;grid-template-columns:repeat(4,1fr);gap:10px}.route-steps a,.route-steps div{display:block;border-top:3px solid #13B8C5;padding:15px;background:white;color:#344C60}.route-steps strong{color:#18364B;display:block}.article-layout{display:grid;grid-template-columns:minmax(0,1fr) 235px;gap:32px;align-items:start}.article-layout>article{min-width:0}.fact-panel,.toc-panel{background:#EAF1F6;border:1px solid #DCE6ED;border-radius:12px;padding:22px;font-size:14px}.toc-panel{position:sticky;top:16px}.toc-panel h2,.fact-panel h2{font-size:18px}.toc-panel a{display:block;padding:7px 0}.article-section{margin:0 0 48px}.article-section h2{border-left:4px solid #13B8C5;padding-left:14px}.article-section h3{margin-top:26px}.table-wrap{overflow-x:auto;max-width:100%;border:1px solid #DCE6ED;border-radius:12px;background:white;margin:22px 0}table{border-collapse:collapse;width:100%;min-width:575px;text-align:left;font-size:15px}caption{text-align:left;font-weight:700;color:#18364B;padding:17px}th,td{border-bottom:1px solid #DCE6ED;padding:13px 15px;vertical-align:top}thead th{background:#EAF1F6;color:#18364B}tbody tr:last-child td{border-bottom:0}.steps{counter-reset:step;list-style:none;padding:0;display:grid;gap:14px}.steps li{counter-increment:step;padding:16px 18px 16px 62px;background:#fff;border-left:3px solid #13B8C5;position:relative}.steps li:before{content:counter(step,decimal-leading-zero);font-weight:800;color:#168796;position:absolute;left:17px}.compare-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:15px}.compare-grid article{padding:22px;background:white;border:1px solid #DCE6ED;border-radius:10px}.definition-list{display:grid;grid-template-columns:1fr 1fr;gap:18px}.definition-list article{border-bottom:1px solid #DCE6ED;padding-bottom:12px}.gallery-grid{display:grid;grid-template-columns:1.15fr .85fr;gap:26px;align-items:start}.gallery-grid article{padding:20px;background:white;border:1px solid #DCE6ED;border-radius:12px}.gallery-grid article:nth-child(2){margin-top:45px}.gallery-grid .media-frame{margin-bottom:20px}.rules-main{max-width:900px;margin-inline:auto}.anchor-strip{display:flex;flex-wrap:wrap;gap:12px;margin:25px 0}.anchor-strip a{padding:9px 14px;background:#EAF1F6;border-radius:8px;font-weight:650}.faq-stack details{background:white;border:1px solid #DCE6ED;border-radius:9px;margin:10px 0;padding:0 18px}.faq-stack summary{cursor:pointer;color:#18364B;font-weight:700;padding:14px 4px}.faq-stack details p{padding:0 4px 15px;margin:0}.service-layout{display:grid;grid-template-columns:235px minmax(0,1fr);gap:35px;align-items:start}.service-nav{background:#EAF1F6;border-radius:10px;padding:22px;position:sticky;top:15px}.service-nav a{display:block;padding:6px 0}.service-content section{margin:0 0 44px}.related{background:#E9F8F8;border-radius:12px;padding:27px;margin-block:45px}.related h2{font-size:22px}.related-links{display:flex;flex-wrap:wrap;gap:12px}.related-links a{display:inline-flex;background:#fff;padding:8px 14px;border:1px solid #b3dfe2;border-radius:8px;font-weight:700}.callout{padding:18px 23px;border-left:4px solid #13B8C5;background:#E9F8F8;margin:20px 0}.site-footer{background:#0B2539;color:#DCECF5;margin-top:64px}.footer-layout{display:grid;grid-template-columns:2fr 1fr;gap:35px;padding:45px 0}.footer-layout p{font-size:14px;max-width:620px}.footer-brand{color:#fff;font-size:22px;font-weight:800}.footer-links{display:grid;grid-template-columns:1fr 1fr;gap:5px 14px;margin-top:14px}.footer-links a{color:#DCECF5;font-size:14px}.footer-bottom{padding:15px 0;border-top:1px solid #24445a;font-size:13px;color:#a6c0d1}.mobile-shortcuts{display:none}.back-top{display:none;position:fixed;right:18px;bottom:20px;z-index:15;background:#102E46;color:white;border:0;border-radius:8px;width:42px;height:42px}.back-top.show{display:block}
@media(max-width:920px){.shell{width:calc(100% - 44px)}.brand-row{height:64px;gap:12px;justify-content:space-between}.brand-note,.desktop-nav{display:none}.menu-toggle{display:flex;flex-direction:column;justify-content:center;gap:5px;width:40px;height:40px;border:0;background:transparent;padding:9px;flex:0 0 40px}.menu-toggle span{height:2px;width:21px;background:#102E46;border-radius:2px}.brand{max-width:calc(100% - 165px)}.brand img{max-height:30px;max-width:100%}.brand-text{font-size:18px}.brand-text small{font-size:8px}.entry-button{margin:0;padding:8px 10px;min-height:39px;font-size:12px;white-space:nowrap}.drawer-overlay{display:block;position:fixed;inset:0;background:rgba(8,24,34,.58);z-index:30;opacity:0;visibility:hidden;pointer-events:none;transition:opacity .2s,visibility .2s}.drawer-overlay.is-visible{opacity:1;visibility:visible;pointer-events:auto}.mobile-drawer{display:block;position:fixed;inset:0 auto 0 0;width:min(86vw,340px);background:white;z-index:31;transform:translateX(-105%);transition:transform .22s;overflow-y:auto;padding:22px;box-shadow:9px 0 25px rgba(0,0,0,.1)}.mobile-drawer.is-open{transform:translateX(0)}.drawer-top{display:flex;justify-content:space-between;align-items:center;border-bottom:1px solid #DCE6ED;padding-bottom:12px}.drawer-close{border:0;background:#EAF1F6;width:40px;height:40px;border-radius:8px;font-size:27px;line-height:1}.mobile-drawer nav p{font-size:13px;font-weight:800;color:#168796;margin:22px 0 5px}.mobile-drawer nav a{display:block;color:#18364B;padding:10px 8px;border-bottom:1px solid #edf1f4}.article-layout{grid-template-columns:minmax(0,1fr) 200px;gap:20px}.mobile-shortcuts{display:flex;justify-content:space-between;flex-wrap:wrap;gap:12px;padding-top:24px}.mobile-shortcuts a{font-size:13px}}@media(max-width:760px){.cover,.split,.split.wide-image,.editor-grid,.article-layout,.service-layout,.gallery-grid,.footer-layout{grid-template-columns:1fr}.service-content{order:0}.service-nav{order:1;position:static}.toc-panel{position:static}.gallery-grid article:nth-child(2){margin-top:0}.compare-grid{grid-template-columns:1fr}.route-steps{grid-template-columns:1fr 1fr}.media-frame--feature{--media-limit:215px}.rule-cards{grid-template-columns:1fr}.rule-cards article:nth-child(2),.rule-cards article:nth-child(3){margin-top:0}.page-header h1{font-size:30px}.cover{padding-top:32px;gap:20px}.cover .media-frame{max-width:650px}.footer-layout{gap:20px}}@media(max-width:640px){body{font-size:15px;line-height:1.78}.shell{width:calc(100% - 32px)}h1{font-size:30px}h2{font-size:22px}h3{font-size:18px}section{margin-block:35px}.page-header{padding:23px 0 0}.page-header h1{font-size:27px}.lead{font-size:16px}.media-frame--hero{--media-limit:205px}.media-frame--feature{--media-limit:185px}.media-frame--card{--media-limit:145px}.media-frame--banner{--media-limit:135px}.media-frame--mobile{--media-limit:285px;max-width:250px}.cover{grid-template-columns:1fr}.topic-directory,.definition-list{grid-template-columns:1fr}.topic-row{padding:16px 0}.feature-story,.soft-section,.note-band{padding:20px}.route-steps{grid-template-columns:1fr}.section-header{align-items:start}.related{padding:20px}.footer-layout{padding:32px 0}.footer-links{grid-template-columns:1fr 1fr}.brand img{max-height:28px}.breadcrumbs{margin:16px 0}}@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*:before,*:after{animation-duration:.01ms!important;transition-duration:.01ms!important}}