:root{--bg:#F4F7FA;--surface:#fff;--soft:#EAF1F6;--pale:#E9F8F8;--navy:#102E46;--deep:#163C57;--teal:#13B8C5;--blue:#237BD3;--heading:#18364B;--text:#344C60;--muted:#64798A;--line:#DCE6ED;--footer:#0B2539}*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:24px}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}a{color:#12649f;text-decoration:none}a:hover{text-decoration:underline}a:focus-visible,button:focus-visible,summary:focus-visible{outline:3px solid #13B8C5;outline-offset:3px}img{max-width:100%;height:auto}h1,h2,h3{font-weight:750;color:var(--heading);line-height:1.38;margin:0 0 .75em}h1{font-size:clamp(32px,3.5vw,40px)}h2{font-size:clamp(24px,2.3vw,28px)}h3{font-size:20px}p{margin:0 0 1.15em}ul,ol{padding-left:1.45em}li+li{margin-top:.45em}section{scroll-margin-top:26px}.container{width:min(1200px,calc(100% - 56px));margin-inline:auto}.page-main{padding-top:30px;padding-bottom:70px;min-height:60vh}.skip-link{position:absolute;top:-100px;left:12px;z-index:100;padding:10px;background:white}.skip-link:focus{top:12px}.site-header{background:var(--surface);box-shadow:0 2px 12px #18364b0c}.brand-bar{height:72px;display:flex;align-items:center;gap:19px}.brand{display:flex;align-items:center;min-width:0}.brand img{display:block;max-height:38px;width:auto;max-width:205px;object-fit:contain}.brand-text{font-size:23px;font-weight:800;color:var(--navy);line-height:1.1}.brand-text small{display:block;font-size:10px;letter-spacing:1.7px}.brand-desc{font-size:13px;color:var(--muted)}.register-link,.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;background:var(--navy);color:#fff;border-radius:9px;padding:9px 20px;font-weight:700;line-height:1.5;min-height:42px}.register-link{margin-left:auto}.register-link:hover,.btn:hover{background:#204b69;text-decoration:none;color:#fff}.btn.secondary{background:#e1f5f6;color:var(--navy);border:1px solid #b9dde2}.btn.secondary:hover{background:#d2edef;color:var(--navy)}.desktop-nav{background:var(--navy)}.nav-inner{display:grid;grid-template-columns:repeat(7,minmax(0,1fr));align-items:stretch}.nav-inner a{color:#eaf5fa;text-align:center;display:flex;align-items:center;justify-content:center;min-height:51px;font-size:14px;font-weight:650;border-bottom:3px solid transparent;padding:8px 3px;white-space:nowrap}.nav-inner a:hover{background:#22465e;text-decoration:none}.nav-inner a[aria-current=page]{border-bottom-color:var(--teal);background:#1a405b;color:#fff;font-weight:800}.menu-toggle{display:none;border:0;background:transparent;padding:8px;width:40px;height:40px;flex:0 0 40px}.menu-toggle span{display:block;height:2px;background:var(--navy);margin:5px 0}.mobile-drawer,.drawer-shade,.mobile-quick{display:none}.nojs-nav{display:flex;flex-wrap:wrap;gap:8px;padding-top:14px}.nojs-nav a{padding:5px 10px;background:#e8f1f5}.eyebrow{text-transform:uppercase;letter-spacing:.12em;color:#167b88;font-weight:800;font-size:12px;margin-bottom:14px}.lead{font-size:17px;line-height:1.85;color:#476175}.lead strong{color:var(--heading)}.breadcrumbs{font-size:13px;margin-bottom:24px;color:var(--muted)}.breadcrumbs span{margin-left:7px}.hero{display:grid;grid-template-columns:1.06fr .94fr;gap:35px;align-items:center;padding:30px 0 48px}.hero h1{font-size:clamp(32px,3.5vw,44px)}.hero-text p{max-width:620px}.hero-actions{display:flex;flex-wrap:wrap;gap:10px;margin-top:20px}.media-frame{display:flex;align-items:center;justify-content:center;min-width:0;width:100%;padding:8px;margin:0;border-radius:14px;background:var(--soft);overflow:visible}.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--mobile{--media-limit:350px;max-width:320px}.media-frame--banner{--media-limit:210px}.media-missing{min-height:115px;color:var(--muted);text-align:center;font-size:13px;border:1px dashed #bfd1df}.media-missing span{max-width:220px}.content-band{margin:0 0 64px}.section-heading{border-bottom:1px solid var(--line);display:flex;justify-content:space-between;align-items:baseline;gap:15px;padding-bottom:15px;margin-bottom:24px}.section-heading h2{margin:0}.small-note,.small{color:var(--muted);font-size:13px}.topic-index{display:grid;grid-template-columns:1fr 1fr;gap:0 34px}.topic-index article{display:grid;grid-template-columns:36px 1fr;gap:14px;padding:20px 0;border-bottom:1px solid var(--line)}.topic-index .number{font-size:14px;font-weight:800;color:#178995}.topic-index h3{font-size:19px;margin-bottom:6px}.topic-index p{font-size:15px;margin-bottom:0}.focus-layout{display:grid;grid-template-columns:1.85fr 1fr;gap:25px}.feature-story{background:white;padding:30px;border-left:5px solid var(--teal);border-radius:0 13px 13px 0}.focus-side{display:grid;gap:17px}.mini-story{background:var(--soft);padding:22px;border-radius:12px}.mini-story p:last-child,.feature-story p:last-child{margin-bottom:0}.split-feature{display:grid;grid-template-columns:.9fr 1.1fr;gap:34px;align-items:center}.split-feature.reverse{grid-template-columns:1.08fr .92fr}.split-feature.reverse .split-copy{order:0}.split-feature.reverse .media-frame{order:1}.split-copy{min-width:0}.text-chips{display:flex;flex-wrap:wrap;gap:9px}.text-chip{background:var(--pale);padding:6px 12px;border-radius:6px;font-size:13px}.lesson-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:17px}.lesson{background:white;padding:24px;border-top:3px solid var(--teal);border-radius:7px}.lesson:nth-child(2){margin-top:18px;border-color:var(--blue)}.lesson:nth-child(3){margin-top:36px;border-color:#8098ac}.reading-route{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:12px;counter-reset:stage}.reading-route article{padding:22px;background:var(--deep);border-radius:9px;color:#e5f3f8}.reading-route article:before{counter-increment:stage;content:'0' counter(stage);color:#6bd9df;font-weight:800;font-size:13px}.reading-route h3{color:white;margin:8px 0}.reading-route p{font-size:14px}.reading-route a{color:#a6f4fa}.editorial-note{border-left:3px solid var(--teal);background:var(--pale);padding:20px 25px}.page-intro{padding:18px 0 30px;max-width:880px}.page-intro h1{font-size:clamp(30px,3vw,36px)}.section-nav{display:flex;gap:8px;flex-wrap:wrap;margin:5px 0 38px}.section-nav a{padding:8px 15px;background:#e0edf3;border:1px solid #c9dce5;color:var(--navy);border-radius:6px;font-size:14px}.article-section{margin:0 0 55px}.article-section>p,.article-section>.narrow{max-width:790px}.reading-column{max-width:800px}.reading-column p{line-height:1.82}.article-grid{display:grid;grid-template-columns:minmax(0,1fr) 250px;gap:36px}.aside-box{padding:20px;background:var(--soft);border-radius:10px;align-self:start}.aside-box h3{font-size:17px}.aside-box p,.aside-box li{font-size:14px}.page-table{width:100%;border-collapse:collapse;background:#fff;font-size:15px}.page-table caption{text-align:left;font-size:14px;font-weight:750;color:var(--heading);padding-bottom:12px}.page-table th,.page-table td{text-align:left;vertical-align:top;border-bottom:1px solid var(--line);padding:13px 15px}.page-table th{background:#dfeaf2;color:var(--heading)}.table-scroll{width:100%;overflow-x:auto;border-radius:10px;border:1px solid var(--line)}.table-scroll table{min-width:620px}.steps{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:12px}.steps article{background:white;padding:18px;border-top:3px solid var(--blue);border-radius:8px}.steps strong{font-size:13px;color:#168692}.steps h3{font-size:17px;margin:6px 0}.steps p{font-size:14px}.vertical-steps{counter-reset:item;list-style:none;padding:0;border-left:2px solid #b5d5df;margin-left:14px}.vertical-steps li{padding:0 0 24px 27px;position:relative}.vertical-steps li:before{counter-increment:item;content:counter(item);position:absolute;left:-17px;top:0;width:30px;height:30px;border-radius:50%;background:var(--navy);color:#fff;text-align:center;line-height:30px;font-size:13px}.callout{background:#e9f8f8;border-left:4px solid var(--teal);padding:20px 25px;margin:24px 0}.comparison-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}.comparison-grid article{background:#fff;padding:24px;border-radius:11px}.gallery-grid{display:grid;grid-template-columns:1fr 1fr;gap:32px;align-items:center}.gallery-grid>div{min-width:0}.gallery-grid .media-frame{margin:0 auto}.gallery-grid.flip .media-frame{order:2}.faq details{background:white;border:1px solid var(--line);border-radius:9px;margin-bottom:9px;padding:0 20px}.faq summary{cursor:pointer;padding:15px 0;font-weight:700;color:var(--heading)}.faq details p{border-top:1px solid var(--line);padding:15px 0;margin:0}.related-links{border-top:1px solid var(--line);padding-top:30px;margin-top:55px}.related-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:11px}.related-link{display:block;padding:16px 18px;background:white;border:1px solid var(--line);border-radius:9px;font-weight:700}.related-link:after{content:' ↗';color:var(--teal)}.about-layout{display:grid;grid-template-columns:230px minmax(0,1fr);gap:38px}.about-aside{align-self:start;position:sticky;top:20px;background:var(--soft);padding:20px;border-radius:10px}.about-aside a{display:block;padding:8px 0}.about-content{min-width:0}.site-footer{background:var(--footer);color:#dcecf5;padding-top:45px}.footer-grid{display:grid;grid-template-columns:1.5fr .7fr 1fr;gap:55px}.site-footer a{color:#b3e8ef}.site-footer nav a{display:block;margin:6px 0}.footer-brand{font-size:21px;color:#fff}.footer-brand span{font-size:12px;letter-spacing:.11em}.site-footer strong{color:#fff}.footer-bottom{border-top:1px solid #315268;padding:14px 0 22px;margin-top:35px;color:#9eb9c8;font-size:13px}.back-top{position:fixed;bottom:22px;right:22px;border:none;color:#fff;background:var(--navy);width:42px;height:42px;border-radius:50%;font-size:21px;opacity:0;pointer-events:none;transition:opacity .2s;z-index:5}.back-top.visible{opacity:1;pointer-events:auto}@media(max-width:1024px){.container{width:calc(100% - 44px)}.hero{gap:22px}.article-grid{grid-template-columns:minmax(0,1fr) 210px;gap:22px}.footer-grid{gap:30px}}@media(max-width:920px){.brand-bar{height:63px;justify-content:space-between;gap:9px}.menu-toggle{display:block}.brand img{max-height:30px;max-width:170px}.brand-text{font-size:18px}.brand-desc,.desktop-nav{display:none}.register-link{font-size:12px;padding:7px 10px;min-height:39px;white-space:nowrap;margin-left:0}.drawer-shade{display:block;position:fixed;inset:0;background:#081c2cb3;opacity:0;visibility:hidden;pointer-events:none;z-index:30;transition:opacity .2s,visibility .2s}.mobile-drawer{display:block;position:fixed;left:0;top:0;bottom:0;width:min(86vw,340px);background:#fff;transform:translateX(-105%);visibility:hidden;z-index:31;overflow-y:auto;transition:transform .2s,visibility .2s;box-shadow:5px 0 30px #0002}.drawer-open .drawer-shade{opacity:1;visibility:visible;pointer-events:auto}.drawer-open .mobile-drawer{transform:translateX(0);visibility:visible}.drawer-head{display:flex;justify-content:space-between;align-items:center;border-bottom:1px solid var(--line);padding:16px 19px}.drawer-close{width:40px;height:40px;border:0;background:var(--soft);font-size:28px;color:var(--navy);border-radius:6px}.mobile-drawer nav{padding:16px 24px 30px}.mobile-drawer nav strong{display:block;color:#167f8b;font-size:12px;letter-spacing:.12em;margin:14px 0 4px}.mobile-drawer nav a{display:block;padding:10px 7px;border-bottom:1px solid var(--line);color:var(--heading)}.mobile-quick{display:flex;justify-content:space-between;flex-wrap:wrap;gap:10px;padding:14px 0 23px;font-size:13px;border-top:1px solid var(--line)}}@media(max-width:760px){.hero,.split-feature,.split-feature.reverse,.focus-layout,.article-grid,.gallery-grid,.about-layout{grid-template-columns:1fr}.hero{padding:12px 0 28px}.hero .media-frame{max-width:650px}.split-feature.reverse .media-frame,.gallery-grid.flip .media-frame{order:0}.split-feature.reverse .split-copy{order:1}.comparison-grid,.lesson-grid{grid-template-columns:1fr 1fr}.lesson:nth-child(3){margin-top:0}.reading-route,.steps{grid-template-columns:repeat(2,minmax(0,1fr))}.about-aside{position:static;order:2}.about-content{order:1}.footer-grid{grid-template-columns:1fr 1fr}.footer-grid>div:first-child{grid-column:1/-1}}@media(max-width:640px){.container{width:calc(100% - 32px)}.page-main{padding-top:20px;padding-bottom:45px}h1,.hero h1{font-size:30px}h2{font-size:22px}h3{font-size:18px}body{font-size:15px;line-height:1.77}.lead{font-size:15.5px}.content-band,.article-section{margin-bottom:39px}.section-heading{align-items:start;flex-direction:column;gap:5px}.topic-index,.comparison-grid,.lesson-grid,.related-grid,.footer-grid{grid-template-columns:1fr}.topic-index article{padding:16px 0}.lesson:nth-child(2){margin-top:0}.feature-story{padding:22px}.section-nav{margin-bottom:25px}.page-intro h1{font-size:27px}.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}.gallery-grid{gap:16px}.footer-grid>div:first-child{grid-column:auto}.footer-grid{gap:18px}.site-footer{padding-top:32px}.brand img{max-width:143px}.brand-text{font-size:16px}.register-link{font-size:11px;padding:6px 8px}.steps,.reading-route{grid-template-columns:1fr}.page-table th,.page-table td{padding:10px 12px}.related-grid{gap:8px}}@media(max-width:370px){.brand img{max-width:126px}.brand-bar{gap:4px}.menu-toggle{padding:7px}.register-link{padding:6px;font-size:11px}.hero-actions .btn{width:100%}}@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*:before,*:after{transition:none!important;animation:none!important}}
