:root{--bg:#F6FAFC;--surface:#fff;--pale:#EAF6FA;--pale2:#EDF4F8;--cyan:#25C8D1;--sky:#25B6E8;--blue:#1787DB;--navy:#174B78;--heading:#183A56;--text:#31485D;--muted:#687D8E;--border:#DCE9F0;--footer:#123653;--radius:16px}*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:28px}body{margin:0;background:var(--bg);color:var(--text);font:16px/1.8 Arial,"PingFang SC","Microsoft YaHei",sans-serif;overflow-x:hidden}img{max-width:100%}a{color:var(--navy);text-underline-offset:4px;text-decoration-thickness:1px}a:hover{color:#0679b0}a:focus-visible,button:focus-visible,summary:focus-visible{outline:3px solid var(--sky);outline-offset:3px}button{font:inherit;cursor:pointer}.container{width:min(100% - 56px,1180px);margin-inline:auto}.section{margin-block:58px}h1,h2,h3{line-height:1.36;color:var(--heading);margin:0 0 18px;letter-spacing:-.02em}h1{font-size:clamp(32px,3.1vw,42px)}.page-intro h1{font-size:clamp(30px,2.9vw,36px)}h2{font-size:clamp(23px,2.2vw,27px)}h3{font-size:20px}p{margin:0 0 17px}ul,ol{padding-left:1.4em;margin:8px 0 20px}li{margin-bottom:8px}small,.eyebrow{font-size:13px;color:var(--muted)}.eyebrow{font-weight:700;letter-spacing:.11em;text-transform:uppercase;color:#087ca2;margin-bottom:9px}.lede{font-size:17px;max-width:780px}.muted{color:var(--muted)}.section-head{display:flex;align-items:flex-end;justify-content:space-between;gap:20px;margin-bottom:22px}.section-head h2{margin-bottom:0}.section-head p{margin:0;max-width:570px}.skip-link{position:absolute;z-index:200;top:-80px;left:12px;background:white;padding:8px 16px}.skip-link:focus{top:8px}.site-header{background:white;box-shadow:0 1px 0 var(--border);position:relative;z-index:20}.toolbar{height:72px;display:flex;align-items:center;gap:20px}.brand{display:inline-flex;align-items:center;min-width:0;text-decoration:none}.brand-fallback{display:flex;align-items:baseline;gap:10px;color:var(--navy);white-space:nowrap}.brand-fallback b{font-size:25px}.brand-fallback small{font-size:11px;letter-spacing:.12em}.toolbar-tag{margin-left:auto;font-size:14px;color:var(--muted)}.entry-btn{margin-left:17px;min-height:42px;padding:8px 22px;display:inline-flex;align-items:center;justify-content:center;text-decoration:none;color:#fff;background:var(--navy);border-radius:10px;font-weight:700;white-space:nowrap}.entry-btn:hover{color:white;background:#0b659c}.menu-toggle{display:none;border:1px solid var(--border);background:white;width:40px;height:40px;border-radius:9px;padding:10px;flex-shrink:0}.menu-toggle span{display:block;height:2px;background:var(--navy);margin:4px 0;border-radius:2px}.desktop-nav{background:var(--navy)}.nav-list{display:flex;align-items:stretch;justify-content:space-between;gap:10px;min-height:48px}.nav-list a{display:flex;align-items:center;padding:10px 11px;color:#ecf8ff;text-decoration:none;white-space:nowrap;font-size:15px;border-bottom:3px solid transparent}.nav-list a:hover,.nav-list a[aria-current="page"]{color:white;border-bottom-color:var(--cyan)}.quick-topics{background:#edf8fa;border-bottom:1px solid var(--border)}.quick-inner{display:flex;justify-content:space-between;gap:20px;flex-wrap:wrap;padding:11px 0}.quick-inner span{display:flex;align-items:center;gap:12px;font-size:13px;flex-wrap:wrap}.quick-inner b{color:var(--heading)}.quick-inner a{text-decoration:none}.drawer-overlay{position:fixed;inset:0;background:rgba(11,34,51,.48);z-index:80;visibility:hidden;opacity:0;pointer-events:none;transition:opacity .2s,visibility .2s}.site-drawer{position:fixed;z-index:81;top:0;left:0;bottom:0;width:min(86vw,344px);background:white;box-shadow:8px 0 30px #12365322;overflow-y:auto;transform:translateX(-105%);visibility:hidden;pointer-events:none;transition:transform .23s,visibility .23s;padding:22px}.menu-open{overflow:hidden}.menu-open .drawer-overlay{opacity:1;visibility:visible;pointer-events:auto}.menu-open .site-drawer{transform:translateX(0);visibility:visible;pointer-events:auto}.drawer-heading{display:flex;justify-content:space-between;align-items:center;margin-bottom:20px}.drawer-heading strong{font-size:20px;color:var(--heading)}.drawer-close{width:40px;height:40px;font-size:28px;border:1px solid var(--border);background:white;border-radius:8px;line-height:1}.drawer-group{padding:10px 0 17px;border-top:1px solid var(--border)}.drawer-group h2{font-size:14px;color:var(--muted);margin:8px 0}.drawer-group a{display:block;padding:9px 8px;text-decoration:none;font-size:16px}.hero{display:grid;grid-template-columns:minmax(0,56fr) minmax(0,44fr);gap:34px;align-items:center;background:linear-gradient(115deg,#fff,#f0f9fb);border:1px solid var(--border);border-radius:22px;padding:32px;margin-top:38px}.hero h1{margin-bottom:19px}.hero p{max-width:570px}.action-row{display:flex;flex-wrap:wrap;gap:14px;margin-top:23px}.action-row a{padding:10px 18px;background:var(--navy);color:white;text-decoration:none;border-radius:9px;font-weight:700}.action-row a+ a{background:white;color:var(--navy);border:1px solid #b1d7e5}.media{display:flex;justify-content:center;align-items:center;width:100%;min-width:0;overflow:hidden;border-radius:14px;background:#EAF6FA;margin:0}.media img{display:block;width:auto;height:auto;max-width:100%;max-height:100%;object-fit:contain;object-position:center}.media--empty{background:linear-gradient(135deg,#e7f5f9,#d9eef6);border:1px solid #cfe7ee;position:relative}.media--empty:after{content:"";width:30%;max-width:95px;aspect-ratio:1;border:1px solid #c1e0eb;border-radius:20%;transform:rotate(15deg);opacity:.48}.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--logo{height:38px;width:auto;max-width:240px;background:none;border:0}.media--logo img{max-height:38px}.media--wide{height:auto;min-height:120px;max-height:240px;aspect-ratio:3/1}.media--portrait{max-width:320px}.feature-with-image{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,.9fr);gap:28px;align-items:center}.feature-with-image.reverse{grid-template-columns:minmax(0,.9fr) minmax(0,1fr)}.feature-with-image.reverse .media{order:-1}.topic-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:15px}.topic-card{min-width:0;padding:22px;background:white;border:1px solid var(--border);border-radius:13px;text-decoration:none;display:block}.topic-card:hover{border-color:var(--sky);box-shadow:0 8px 26px #174b7810}.topic-card strong{font-size:18px;display:block;color:var(--heading);margin-bottom:7px}.topic-card p{font-size:14px;line-height:1.7;color:var(--text);margin:0}.editor-grid{display:grid;grid-template-columns:2fr 1fr;gap:18px}.editor-lead,.editor-side article,.content-card,.note-box,.guide-step,.matrix-cell{background:white;border:1px solid var(--border);border-radius:14px;padding:24px}.editor-lead{background:var(--pale)}.editor-side{display:grid;gap:18px}.editor-grid h3{margin-bottom:12px}.text-link{font-weight:700;text-decoration-thickness:1px}.triple-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}.triple-grid article{padding:24px;border-top:3px solid var(--cyan);background:white;border-radius:8px 8px 14px 14px;border-inline:1px solid var(--border);border-bottom:1px solid var(--border)}.triple-grid article span{font-size:30px;color:#168fba;font-weight:700}.reading-path{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:12px;list-style:none;padding:0}.reading-path li{background:#edf4f8;padding:17px;border-radius:12px}.reading-path b{display:block;color:var(--navy)}.editor-disclaimer{padding:21px 24px;border-left:3px solid var(--cyan);background:white;border-radius:0 12px 12px 0;font-size:14px}.page-intro{padding:36px 0 9px}.page-intro .lede{max-width:830px}.prose{max-width:780px}.prose p{margin-bottom:19px}.article-section{margin:38px 0}.article-section h2{padding-bottom:10px;border-bottom:1px solid var(--border)}.article-section h3{margin-top:20px}.split-layout{display:grid;grid-template-columns:minmax(0,760px) minmax(210px,240px);gap:50px;align-items:start}.side-note{background:var(--pale);padding:20px;border-radius:14px;position:sticky;top:24px}.side-note h2{font-size:19px}.side-note dt{font-weight:700;color:var(--heading)}.side-note dd{margin:0 0 14px;font-size:14px}.table-wrap{overflow-x:auto;border:1px solid var(--border);border-radius:12px;background:white}.data-table{border-collapse:collapse;width:100%;min-width:510px;font-size:15px}.data-table th,.data-table td{padding:14px 17px;border-bottom:1px solid var(--border);text-align:left;vertical-align:top}.data-table th{background:var(--pale);color:var(--heading);font-weight:700}.data-table tr:last-child td{border-bottom:0}.number-steps{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px;counter-reset:step}.number-steps article{counter-increment:step;background:white;padding:22px;border:1px solid var(--border);border-radius:12px}.number-steps article:before{content:counter(step,decimal-leading-zero);display:block;font-size:25px;font-weight:700;color:#168fb8;margin-bottom:9px}.matrix{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:14px}.matrix-cell{padding:21px}.matrix-cell h3{font-size:19px}.matrix-cell p{font-size:15px}.gallery{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:20px}.gallery figure{margin:0;background:white;border:1px solid var(--border);border-radius:14px;padding:15px}.gallery figcaption{font-size:14px;padding:10px 5px 2px}.gallery strong{display:block;color:var(--heading);font-size:17px}.related{background:var(--pale);padding:26px;border-radius:15px;margin-block:50px}.related h2{font-size:22px}.related-links{display:flex;flex-wrap:wrap;gap:13px}.related-links a{background:white;padding:12px 17px;text-decoration:none;border-radius:9px;font-weight:700}.faq-list details{background:white;border:1px solid var(--border);margin-bottom:10px;border-radius:10px;padding:0 18px}.faq-list summary{padding:14px 8px;cursor:pointer;font-weight:700;color:var(--heading)}.faq-list details p{padding:0 8px 14px;margin:0}.anchor-nav{display:flex;flex-wrap:wrap;gap:10px;margin:18px 0 28px}.anchor-nav a{padding:8px 13px;background:var(--pale);border-radius:8px;text-decoration:none}.callout{background:#e8f7fa;border-left:4px solid var(--cyan);padding:19px 22px;border-radius:0 9px 9px 0}.site-footer{background:var(--footer);color:#eaf7ff;margin-top:66px;padding:46px 0 16px}.footer-grid{display:grid;grid-template-columns:1fr 1fr;gap:60px}.footer-brand{font-size:23px;font-weight:700}.footer-brand small{color:#a0dfea;margin-left:8px}.footer-notice{max-width:600px;font-size:13px;color:#c2dbe8}.site-footer h2{color:white;font-size:17px}.footer-links{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:5px 12px}.site-footer a{color:#eaf7ff}.footer-bottom{padding-top:20px;margin-top:30px;border-top:1px solid #ffffff30;display:flex;justify-content:space-between;gap:20px;flex-wrap:wrap;font-size:13px;color:#b8d2e1}.mobile-bottom{display:none}.back-top{position:fixed;right:20px;bottom:23px;width:44px;height:44px;border-radius:10px;background:var(--navy);border:0;color:white;z-index:30;opacity:0;visibility:hidden;pointer-events:none;transition:opacity .2s}.back-top.visible{opacity:1;visibility:visible;pointer-events:auto}@media(max-width:980px){.container{width:min(100% - 44px,1180px)}.toolbar{height:62px;justify-content:space-between}.menu-toggle{display:block}.brand{margin-right:auto}.toolbar-tag,.desktop-nav{display:none}.entry-btn{margin-left:auto;font-size:14px;padding:8px 15px;min-height:40px}.media--logo{height:30px}.media--logo img{max-height:30px}.topic-grid{grid-template-columns:repeat(3,minmax(0,1fr))}.quick-inner{justify-content:flex-start}.site-footer{margin-bottom:60px}.mobile-bottom{display:grid;grid-template-columns:repeat(4,1fr);position:fixed;bottom:0;left:0;right:0;background:white;z-index:25;box-shadow:0 -2px 12px #1236531a;padding-bottom:env(safe-area-inset-bottom)}.mobile-bottom a{text-align:center;padding:11px 3px;font-size:13px;text-decoration:none;font-weight:700}.back-top{bottom:80px}}@media(max-width:760px){.hero,.feature-with-image,.feature-with-image.reverse,.editor-grid,.split-layout,.footer-grid{grid-template-columns:1fr}.hero{padding:25px}.feature-with-image.reverse .media{order:0}.topic-grid,.matrix{grid-template-columns:repeat(2,minmax(0,1fr))}.triple-grid,.number-steps{grid-template-columns:1fr}.gallery{grid-template-columns:1fr 1fr}.side-note{position:static}.reading-path{grid-template-columns:repeat(2,minmax(0,1fr))}.section{margin-block:38px}.page-intro{padding-top:28px}}@media(max-width:640px){body{font-size:15px;line-height:1.77}.container{width:calc(100% - 32px)}h1{font-size:29px}.page-intro h1{font-size:27px}h2{font-size:22px}h3{font-size:18px}.lede{font-size:16px}.hero{margin-top:22px;padding:20px;gap:23px}.hero .media{order:-1}.action-row a{font-size:14px;padding:10px 12px}.brand-fallback b{font-size:20px}.brand-fallback small{display:none}.topic-grid,.gallery{grid-template-columns:1fr}.topic-card{padding: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:95px;max-height:155px}.editor-lead,.editor-side article,.content-card,.note-box,.guide-step,.matrix-cell{padding:19px}.section-head{display:block}.reading-path{gap:9px}.reading-path li{padding:13px}.quick-inner{gap:8px}.quick-inner span{gap:8px}.quick-inner b{width:100%}.footer-grid{gap:25px}.site-footer{padding-top:32px}.footer-bottom{gap:5px}.back-top{right:14px}}@media(max-height:500px) and (max-width:980px){.mobile-bottom{position:static}.site-footer{margin-bottom:0}.back-top{bottom:18px}}@media(prefers-reduced-motion:reduce){*,*:before,*:after{scroll-behavior:auto!important;transition:none!important;animation:none!important}}