:root{--bg:#f4f7fa;--paper:#fff;--pale:#eaf1f6;--mint:#e9f8f8;--navy:#102e46;--deep:#163c57;--teal:#13b8c5;--blue:#237bd3;--title:#18364b;--text:#344c60;--muted:#64798a;--line:#dce6ed;--footer:#0b2539;--max:1200px}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);font-family:Arial,'PingFang SC','Microsoft YaHei',sans-serif;color:var(--text);line-height:1.8;overflow-wrap:break-word}a{color:#176cb7;text-underline-offset:3px}a:hover{color:#0c5b93}a:focus-visible,button:focus-visible,summary:focus-visible{outline:3px solid #13b8c5;outline-offset:3px}button{font:inherit;cursor:pointer}p{margin:0 0 1.15em}h1,h2,h3{color:var(--title);line-height:1.38;margin:0 0 .65em}h1{font-size:clamp(27px,3.2vw,42px);letter-spacing:-.03em}h2{font-size:clamp(21px,2.3vw,27px)}h3{font-size:clamp(18px,1.7vw,21px)}strong{color:var(--title)}.container{max-width:var(--max);margin:auto;padding:0 28px;min-width:0}.site-main>.container{padding-top:25px;padding-bottom:72px}.section{margin-top:58px}.section>.section-head{margin-bottom:26px}.eyebrow{display:block;color:#137b8b;font-weight:700;letter-spacing:.15em;text-transform:uppercase;font-size:12px;margin-bottom:14px}.lead{font-size:17px;max-width:820px;line-height:1.83}.muted,.meta{color:var(--muted)}.reading-column{max-width:780px}.small-text{font-size:14px}.skip-link{position:absolute;top:-100px;left:10px;z-index:200;background:#fff;padding:10px}.skip-link:focus{top:10px}.site-header{background:var(--navy);color:#fff}.brand-bar{background:#fff}.brand-inner{height:72px;display:flex;align-items:center;gap:22px}.brand{display:flex;align-items:center;text-decoration:none;color:var(--navy);min-width:0}.brand .media-frame{background:transparent;padding:0;border:0;max-height:38px;width:auto}.brand .media-frame img{max-height:38px;width:auto;max-width:210px}.brand .media-missing{display:none}.brand-fallback{font-weight:800;font-size:20px;letter-spacing:.02em;white-space:nowrap}.brand-fallback b{color:#0e9fae}.brand:has(img) .brand-fallback{display:none}.brand-note{font-size:13px;color:var(--muted);border-left:1px solid var(--line);padding-left:20px}.register-link{margin-left:auto;background:var(--navy);color:#fff;border-radius:8px;min-height:42px;padding:7px 23px;text-decoration:none;font-weight:700;white-space:nowrap;display:inline-flex;align-items:center}.register-link:hover{background:#21607a;color:#fff}.desktop-nav{background:var(--navy)}.nav-inner{display:flex;align-items:stretch;justify-content:space-between;gap:5px;min-width:0}.desktop-nav a{color:#eaf5f8;text-decoration:none;font-size:15px;white-space:nowrap;text-align:center;min-width:0;padding:13px 7px 12px;border-bottom:3px solid transparent}.desktop-nav a:hover,.desktop-nav a[aria-current]{color:#fff;border-bottom-color:var(--teal);font-weight:700}.menu-button{display:none;width:40px;height:40px;flex:0 0 40px;border:1px solid var(--line);background:#fff;border-radius:8px;padding:8px;align-items:center;justify-content:center;flex-direction:column;gap:5px}.menu-button span{width:20px;height:2px;background:var(--navy)}.noscript-nav{display:none}.crumb{font-size:13px;display:flex;gap:12px;color:var(--muted);margin-bottom:27px}.crumb a{text-decoration:none}.page-heading{padding:28px 0 22px;border-bottom:1px solid var(--line);margin-bottom:36px}.page-heading h1{font-size:clamp(25px,2.8vw,36px)}.page-heading .lead{margin-bottom:0}.media-frame{display:flex;align-items:center;justify-content:center;min-width:0;width:100%;padding:8px;background:var(--pale);border-radius:14px;--media-limit:220px}.media-frame img{display:block;width:auto;height:auto;max-width:100%;max-height:var(--media-limit);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-frame--logo{--media-limit:38px}.media-missing{min-height:105px;color:var(--muted);font-size:13px;background:repeating-linear-gradient(135deg,#eaf1f6,#eaf1f6 12px,#f4f7fa 12px,#f4f7fa 24px);text-align:center}.media-frame--hero.media-missing{min-height:210px}.media-frame--mobile.media-missing{min-height:220px}.hero{display:grid;grid-template-columns:52fr 48fr;gap:38px;align-items:center;padding:38px 0 30px}.hero-copy .lead{font-size:17px}.hero-actions{display:flex;flex-wrap:wrap;gap:12px;margin-top:26px}.button{display:inline-flex;align-items:center;justify-content:center;text-decoration:none;font-weight:700;padding:11px 20px;border-radius:9px;min-height:44px;background:var(--navy);color:#fff}.button:hover{color:#fff;background:#20506d}.button--secondary{background:var(--mint);color:var(--navy);border:1px solid #b9dfe1}.button--secondary:hover{background:#dcf4f5;color:var(--navy)}.topic-grid{display:grid;grid-template-columns:1fr 1fr;gap:0 42px;border-top:2px solid var(--deep)}.topic-item{padding:23px 0;border-bottom:1px solid var(--line)}.topic-item .number{color:#148793;display:block;font-size:12px;font-weight:700;letter-spacing:.12em}.topic-item h3{margin:4px 0 8px}.topic-item p{margin:0 0 7px}.topic-item a{font-weight:700}.feature-grid{display:grid;grid-template-columns:2fr 1fr;gap:22px}.feature-primary{background:var(--deep);padding:30px;color:#e9f2f7;border-radius:14px}.feature-primary h3,.feature-primary strong{color:#fff}.feature-primary a{color:#83edf0}.feature-side{display:grid;gap:14px}.feature-side article{background:#fff;border:1px solid var(--line);border-radius:12px;padding:23px}.feature-side p:last-child{margin-bottom:0}.split{display:grid;grid-template-columns:1fr 1fr;align-items:center;gap:40px}.split--reverse .media-frame{order:2}.split>*{min-width:0}.text-band{background:var(--mint);padding:28px;border-left:4px solid var(--teal);border-radius:0 12px 12px 0}.panel{background:var(--paper);border:1px solid var(--line);border-radius:12px;padding:24px;min-width:0}.panel--muted{background:var(--pale)}.note{border-left:3px solid var(--teal);padding:14px 20px;background:var(--mint);border-radius:0 9px 9px 0}.list-clean{padding-left:20px}.list-clean li{margin:8px 0}.lesson-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:18px}.lesson-grid article:nth-child(2){margin-top:22px}.lesson-grid article:nth-child(3){margin-top:44px}.path-flow{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:16px;counter-reset:steps}.path-flow>div{border-top:3px solid var(--teal);padding:17px 8px 0 0}.path-flow b{display:block;color:#138f9d;font-size:13px;margin-bottom:7px}.path-flow a{font-weight:700}.editorial-note{padding:20px 26px;background:#e8eef3;border-radius:12px;font-size:15px}.index-columns{display:grid;grid-template-columns:minmax(0,2.2fr) minmax(220px,.8fr);gap:38px}.sticky-index{align-self:start;background:var(--pale);padding:24px;border-radius:12px}.sticky-index a{display:block;padding:8px 0;text-decoration:none;border-bottom:1px solid var(--line)}.article-block{margin-top:44px;scroll-margin-top:24px}.article-block:first-child{margin-top:0}.article-block p{max-width:780px}.comparison{overflow-x:auto;max-width:100%;border:1px solid var(--line);border-radius:12px;background:#fff}.comparison table{border-collapse:collapse;width:100%;min-width:575px;text-align:left;line-height:1.65}.comparison caption{font-weight:700;color:var(--title);text-align:left;padding:15px 17px;background:var(--pale)}.comparison th,.comparison td{padding:13px 16px;border-top:1px solid var(--line);vertical-align:top}.comparison th{background:#f1f6f9;color:var(--title)}.steps{counter-reset:stepp;list-style:none;padding:0;margin:18px 0}.steps li{counter-increment:stepp;padding:15px 15px 15px 60px;position:relative;border-bottom:1px solid var(--line)}.steps li::before{content:counter(stepp,decimal-leading-zero);position:absolute;left:5px;top:14px;color:#008e9d;font-weight:800}.tag{font-size:12px;font-weight:700;color:#137785;letter-spacing:.12em}.matrix{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:14px}.matrix .panel{border-top:4px solid var(--teal)}.gallery{display:grid;grid-template-columns:1fr 1fr;gap:30px 34px;align-items:start}.gallery figure{margin:0;min-width:0}.gallery figure:nth-child(even){margin-top:38px}.gallery figcaption{font-size:15px;padding:14px 3px}.gallery figcaption strong{display:block;font-size:18px}.faq-list details{background:#fff;border:1px solid var(--line);border-radius:9px;margin:9px 0;padding:0 18px}.faq-list summary{font-weight:700;color:var(--title);cursor:pointer;padding:14px 5px}.faq-list details p{padding:0 5px 14px;margin:0}.related-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:15px}.related-link{display:flex;flex-direction:column;text-decoration:none;background:#fff;border:1px solid var(--line);border-radius:10px;padding:19px;gap:8px}.related-link strong{font-size:18px}.related-link span:nth-child(2){flex:1;color:var(--text)}.related-link span:last-child{font-size:20px;color:#1296a3}.anchor-list{display:flex;flex-wrap:wrap;gap:10px;margin:16px 0 26px}.anchor-list a{display:inline-flex;background:var(--pale);padding:7px 14px;border-radius:7px;text-decoration:none;font-weight:700}.about-layout{display:grid;grid-template-columns:225px minmax(0,1fr);gap:35px}.about-side{align-self:start;background:var(--pale);border-radius:12px;padding:20px}.about-side a{display:block;padding:9px 0}.mobile-shortcuts{display:none}.site-footer{background:var(--footer);color:#dcecf5;padding:45px 0 16px}.footer-layout{display:grid;grid-template-columns:2fr 1fr;gap:80px}.footer-brand{font-weight:800;font-size:21px;color:#fff}.footer-brand span{color:#71d9df;font-size:13px;letter-spacing:.08em;margin-left:8px}.site-footer p{max-width:670px;margin:10px 0}.site-footer .fine-print{color:#c6d7e2;font-size:13px}.site-footer nav{display:grid;grid-template-columns:1fr 1fr;gap:7px 14px}.site-footer a{color:#dcecf5;text-decoration:none}.copyright{font-size:12px;color:#b8cad5;border-top:1px solid #335063;margin-top:30px;padding-top:15px}.drawer-overlay{position:fixed;inset:0;background:rgba(7,27,40,.55);z-index:90;opacity:0;visibility:hidden;pointer-events:none;transition:opacity .2s,visibility .2s}.drawer-overlay.is-visible{visibility:visible;pointer-events:auto;opacity:1}.drawer-overlay[hidden]{display:none!important}.mobile-drawer{position:fixed;left:0;top:0;bottom:0;z-index:100;width:min(86vw,340px);background:#fff;transform:translateX(-105%);visibility:hidden;pointer-events:none;transition:transform .24s,visibility .24s;overflow:auto;padding:18px 23px}.mobile-drawer.is-open{transform:translateX(0);visibility:visible;pointer-events:auto}.drawer-open{overflow:hidden}.drawer-top{display:flex;justify-content:space-between;align-items:center;border-bottom:1px solid var(--line);padding-bottom:15px}.drawer-top button{font-size:30px;border:0;background:var(--pale);width:40px;height:40px;border-radius:9px;line-height:1}.drawer-group{padding:17px 0;border-bottom:1px solid var(--line)}.drawer-group span{color:#157c8a;font-size:12px;font-weight:800;letter-spacing:.2em}.drawer-group a{display:block;text-decoration:none;padding:8px 0;color:var(--navy);font-weight:700}.back-top{position:fixed;right:20px;bottom:22px;border:0;border-radius:50%;background:var(--navy);color:#fff;width:44px;height:44px;box-shadow:0 5px 16px #102e4633}.back-top[hidden]{display:none}section[id],div[id]{scroll-margin-top:25px}@media(max-width:1050px){.container{padding-left:22px;padding-right:22px}.brand-note{font-size:12px}}@media(max-width:920px){.brand-inner{height:62px;display:grid;grid-template-columns:40px minmax(0,1fr) auto;gap:10px}.menu-button{display:flex}.brand{justify-self:center}.brand .media-frame img{max-height:30px;max-width:165px}.brand-fallback{font-size:16px}.brand-note,.desktop-nav{display:none}.register-link{margin:0;min-height:40px;padding:6px 12px;font-size:13px}.noscript-nav{display:none}.site-header:has(noscript){} .hero{gap:25px}.footer-layout{gap:30px}.mobile-shortcuts{display:block;background:#e6f0f4}.mobile-shortcuts>.container{display:flex;gap:17px;justify-content:center;flex-wrap:wrap;padding-top:13px;padding-bottom:13px}.mobile-shortcuts a{font-size:13px;text-decoration:none;font-weight:700}}@media(max-width:760px){.split,.feature-grid,.index-columns,.about-layout,.footer-layout{grid-template-columns:1fr}.split--reverse .media-frame{order:0}.lesson-grid,.matrix,.related-grid{grid-template-columns:1fr 1fr}.lesson-grid article:nth-child(n){margin-top:0}.path-flow{grid-template-columns:1fr 1fr}.gallery{gap:18px}.gallery figure:nth-child(even){margin-top:20px}.hero{grid-template-columns:1fr}.hero-media{order:2}.about-side{order:2}.feature-side{grid-template-columns:1fr 1fr}.footer-layout nav{max-width:450px}.section{margin-top:42px}}@media(max-width:640px){.container{padding-left:16px;padding-right:16px}.site-main>.container{padding-top:20px;padding-bottom:46px}.page-heading{padding-top:14px;margin-bottom:26px}.hero{padding:16px 0 12px}.lead,.hero-copy .lead{font-size:15.5px}.topic-grid,.lesson-grid,.matrix,.gallery,.related-grid,.feature-side{grid-template-columns:1fr}.topic-item{padding:18px 0}.feature-primary,.feature-side article,.panel{padding:19px}.path-flow{gap:12px}.gallery figure:nth-child(even){margin-top:0}.media-frame--hero{--media-limit:205px}.media-frame--feature{--media-limit:185px}.media-frame--card{--media-limit:145px}.media-frame--mobile{--media-limit:285px;max-width:250px}.media-frame--banner{--media-limit:135px}.media-frame--logo{--media-limit:30px}.media-frame--hero.media-missing{min-height:140px}.section{margin-top:35px}.footer-brand span{display:block;margin:0}.site-footer{padding-top:32px}.hero-actions{gap:9px}.button{padding:10px 14px}.comparison table{font-size:14px}.steps li{padding-left:52px}}@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*:before,*:after{transition:none!important;animation:none!important}}@media(max-width:920px){body:not(:has(script[src="/script.js"])) .noscript-nav{display:block}} 

@media(max-width:920px){.noscript-nav{display:block}.noscript-nav a{display:inline-block;margin:4px 8px;color:#fff;font-size:13px}.noscript-nav{padding:8px 15px;background:#102e46}}