:root{--bg:#f6fafc;--paper:#fff;--tint:#eaf6fa;--tint2:#edf4f8;--brand:#25c8d1;--sky:#25b6e8;--blue:#1787db;--navy:#174b78;--heading:#183a56;--text:#31485d;--muted:#687d8e;--line:#dce9f0;--footer:#123653;--shell:1180px}*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:25px}body{margin:0;background:var(--bg);font:16px/1.8 Arial,'PingFang SC','Microsoft YaHei',sans-serif;color:var(--text);overflow-x:hidden}body.drawer-open{overflow:hidden}img{max-width:100%}a{color:var(--navy);text-underline-offset:4px}a:hover{color:#087eab}a:focus-visible,button:focus-visible,summary:focus-visible{outline:3px solid var(--brand);outline-offset:3px}button{font:inherit;cursor:pointer}h1,h2,h3{color:var(--heading);line-height:1.36;letter-spacing:-.02em}h1{font-size:clamp(27px,3.1vw,42px);margin:12px 0 22px}h2{font-size:clamp(21px,2.3vw,27px);margin:0 0 17px}h3{font-size:19px;margin:0 0 10px}p{margin:0 0 18px}ul,ol{padding-left:1.35em;margin-top:0}li{margin-bottom:8px}.shell{width:min(var(--shell),calc(100% - 56px));margin-inline:auto}.skip-link{position:absolute;left:10px;top:-80px;background:#fff;padding:8px 14px;z-index:100}.skip-link:focus{top:10px}.site-header{background:#fff;border-bottom:1px solid var(--line);position:relative;z-index:20}.topbar{height:72px;display:flex;align-items:center;gap:25px}.brand{color:var(--heading);text-decoration:none;display:flex;align-items:center;min-width:0}.brand img{display:block;height:auto;max-height:38px;width:auto;max-width:220px;object-fit:contain}.brand>span{font-size:24px;font-weight:800;line-height:1.1;white-space:nowrap}.brand 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.mobile-drawer{visibility:visible;transform:translateX(0);pointer-events:auto}.drawer-top{display:flex;justify-content:space-between;align-items:center;font-weight:800;font-size:19px;margin-bottom:19px}.drawer-close{background:var(--tint);border:0;border-radius:8px;width:40px;height:40px;font-size:28px;line-height:1}.drawer-group-title{font-size:12px;letter-spacing:.13em;color:var(--muted);border-top:1px solid var(--line);padding-top:14px;margin:20px 0 8px}.mobile-drawer>a{display:block;padding:8px 11px;text-decoration:none;border-radius:8px}.mobile-drawer>a.is-current{background:var(--tint);font-weight:700}.section{margin:56px 0}.section-heading{margin-bottom:23px}.eyebrow{display:block;color:#077d97;font-size:12px;font-weight:800;letter-spacing:.13em;text-transform:uppercase;margin:0 0 8px}.section-heading h2{margin:0}.page-intro{padding:43px 0 29px;max-width:920px}.page-intro h1{font-size:clamp(25px,2.9vw,36px);margin:8px 0 15px}.lead{font-size:17px;line-height:1.85;color:#4c6476;max-width:850px}.hero{display:grid;grid-template-columns:56fr 44fr;gap:34px;align-items:center;padding:45px 0 32px}.hero-text>p:not(.eyebrow){font-size:17px;max-width:620px}.hero-actions{display:flex;gap:12px;flex-wrap:wrap;margin-top:25px}.button-outline{display:inline-flex;align-items:center;justify-content:center;border:1px solid #abc9da;color:var(--navy);border-radius:11px;padding:10px 18px;text-decoration:none;font-weight:700}.button-outline:hover{background:#eaf6fa}.media{display:flex;align-items:center;justify-content:center;width:100%;min-width:0;overflow:hidden;border-radius:14px;background:var(--tint);border:1px solid var(--line)}.media img{display:block;width:auto;height:auto;max-width:100%;max-height:100%;object-fit:contain;object-position:center}.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--wide{height:auto;min-height:110px;max-height:230px}.media--wide img{max-height:220px}.media--empty{position:relative}.empty-art{display:block;width:41%;height:47%;border-radius:18px;border:1px solid #c9e1eb;background:linear-gradient(125deg,#eaf6fa 45%,#d8edf4)}.topic-bar{background:#fff;border-block:1px solid var(--line);padding:14px 0}.topic-bar-inner{display:flex;gap:22px;flex-wrap:wrap}.topic-bar-group{font-size:13px;display:flex;gap:11px;align-items:center;flex-wrap:wrap}.topic-bar-group strong{color:var(--heading)}.topic-bar-group a{font-size:13px}.topic-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:14px}.topic-card,.info-card,.quote-card{padding:23px;border:1px solid var(--line);border-radius:14px;background:white;min-width:0}.topic-card{display:block;color:inherit;text-decoration:none}.topic-card:hover{border-color:#75ccd9;transform:translateY(-2px)}.topic-card h3{font-size:18px;margin-bottom:8px}.topic-card p{font-size:14px;color:var(--muted);margin:0}.topic-card .arrow{color:#1687bb;font-size:22px}.feature-split{display:grid;grid-template-columns:2fr 1fr;gap:16px}.feature-primary{background:#fff;border:1px solid var(--line);padding:28px;border-radius:16px}.feature-primary p,.feature-side p{margin-bottom:11px}.feature-side{display:grid;gap:16px}.feature-side article{border:1px solid var(--line);background:var(--tint2);border-radius:14px;padding:20px}.feature-side h3{font-size:18px}.split{display:grid;grid-template-columns:1fr 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16px;border-bottom:1px solid var(--line);vertical-align:top}th{background:var(--tint);color:var(--heading)}tr:last-child td{border-bottom:0}.timeline{border-left:3px solid #65ccd3;padding-left:25px}.timeline article{position:relative;margin-bottom:24px}.timeline article:before{content:'';position:absolute;top:9px;left:-33px;width:13px;height:13px;border:3px solid #fff;background:#1689a9;border-radius:50%}.timeline h3{margin:0 0 5px}.timeline p{margin:0}.article-layout{display:grid;grid-template-columns:minmax(0,760px) minmax(0,240px);gap:40px;align-items:start}.glossary{padding:22px;background:var(--tint2);border:1px solid var(--line);border-radius:12px}.glossary dl{margin:0}.glossary dt{color:var(--heading);font-weight:700}.glossary dd{margin:0 0 17px;color:var(--muted);font-size:14px}.matrix{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:15px}.matrix article{background:#fff;border-top:4px solid var(--brand);border-radius:12px;padding:22px;border-inline:1px solid var(--line);border-bottom:1px solid var(--line)}.matrix p{font-size:15px}.gallery{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:19px}.gallery figure{margin:0;border:1px solid var(--line);padding:14px;border-radius:14px;background:white}.gallery figcaption{padding:13px 3px 5px;font-size:15px}.gallery strong{color:var(--heading)}.reading-toc{display:flex;gap:10px;flex-wrap:wrap;margin:20px 0 29px}.reading-toc a{padding:8px 14px;background:var(--tint);border-radius:8px;font-weight:700;text-decoration:none;font-size:14px}.notice{background:var(--tint);border-left:4px solid var(--brand);padding:16px 20px;border-radius:8px}.faq{max-width:900px}.faq details{background:#fff;border:1px solid var(--line);margin-bottom:10px;border-radius:10px;padding:0 18px}.faq summary{cursor:pointer;color:var(--heading);font-weight:700;padding:14px 0}.faq details p{font-size:15px;margin:0 0 16px}.related{margin:64px 0;background:var(--tint2);border:1px solid 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@media(max-width:1180px){.shell{width:calc(100% - 44px)}.topic-grid{grid-template-columns:repeat(3,minmax(0,1fr))}.article-layout{grid-template-columns:minmax(0,1fr) 220px;gap:24px}}
@media(max-width:980px){.topbar{height:64px;justify-content:space-between;gap:10px}.menu-toggle{display:block;flex:none}.topbar .brand{margin-inline:auto}.brand img{max-height:30px;max-width:180px}.brand>span{font-size:20px}.brand small{font-size:8px}.topbar-tagline,.desktop-nav{display:none}.entry-button{padding:9px 12px;font-size:13px}.topic-bar-inner{gap:12px}.hero{gap:22px}.article-layout{grid-template-columns:1fr}.glossary{max-width:780px}.bottom-nav{display:flex;position:fixed;bottom:0;left:0;right:0;z-index:15;background:#fff;border-top:1px solid var(--line);justify-content:space-around;padding:8px 0 calc(8px + env(safe-area-inset-bottom));box-shadow:0 -3px 14px rgba(10,42,56,.06)}.bottom-nav a{font-size:13px;text-decoration:none;font-weight:700;padding:6px 12px}.site-footer{padding-bottom:calc(85px + env(safe-area-inset-bottom))}.back-to-top{bottom:85px}}
@media(max-width:760px){.hero,.split,.feature-split,.footer-grid{grid-template-columns:1fr}.hero{padding-top:27px}.hero .media{order:2}.hero-text{order:1}.split.reverse>.media{order:0}.topic-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.matrix,.three-up{grid-template-columns:1fr}.steps{grid-template-columns:repeat(2,minmax(0,1fr))}.gallery{grid-template-columns:1fr}.related-links{grid-template-columns:1fr}.section{margin:38px 0}.feature-side{grid-template-columns:1fr 1fr}.page-intro{padding:29px 0 14px}}
@media(max-width:640px){body{font-size:15px;line-height:1.76}.shell{width:calc(100% - 32px)}.topbar{height:62px}.brand img{max-height:28px;max-width:136px}.brand>span{font-size:18px}.brand small{letter-spacing:.12em;font-size:7px}.entry-button{height:39px;padding:8px 10px;font-size:12px}.entry-button span{display:none}.hero h1{font-size:30px}.hero-text>p:not(.eyebrow),.lead{font-size:15px}.hero{gap:18px}.topic-grid{gap:10px}.topic-card,.info-card,.quote-card{padding:16px}.topic-card h3{font-size:16px}.topic-card p{font-size:13px}.feature-primary{padding:20px}.feature-side{grid-template-columns:1fr}.soft-panel{padding:20px}.steps{gap:9px}.steps article{padding:14px}.steps h3{font-size:16px}.section-heading{margin-bottom:18px}.media--hero{height:200px}.media--feature{height:180px}.media--card{height:145px}.media--banner{height:150px}.media--mobile{height:290px;max-width:250px}.media--wide{height:auto;min-height:80px}.media--wide img{max-height:155px}.footer-grid{gap:25px}.footer-links{grid-template-columns:repeat(2,minmax(0,1fr))}.page-intro h1{font-size:27px}.related{padding:17px}}
@media(max-height:500px) and (max-width:980px){.bottom-nav{position:static}.site-footer{padding-bottom:24px}.back-to-top{bottom:20px}}
@media(prefers-reduced-motion:reduce){*,*:before,*:after{scroll-behavior:auto!important;transition:none!important;animation:none!important}}

.nojs-nav{display:flex;flex-wrap:wrap;gap:12px;padding-block:15px}.nojs-nav a{font-size:14px}.steps--three{grid-template-columns:repeat(3,minmax(0,1fr))}@media(max-width:640px){.steps--three{grid-template-columns:1fr}}