:root{--bg:#F6FAFC;--surface:#fff;--soft:#EAF6FA;--soft2:#EDF4F8;--cyan:#25C8D1;--blue:#1787DB;--navy:#174B78;--heading:#183A56;--text:#31485D;--muted:#687D8E;--line:#DCE9F0;--footer:#123653;--max:1180px}*{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}body.drawer-open{overflow:hidden}a{color:var(--navy);text-decoration-color:#8dc8df;text-underline-offset:4px}a:hover{color:#087aa9}button{font:inherit}a:focus-visible,button:focus-visible,summary:focus-visible{outline:3px solid #1787DB;outline-offset:4px}.container{width:min(var(--max),calc(100% - 56px));margin-inline:auto}.site-header{background:#fff;position:relative;z-index:20;border-bottom:1px solid var(--line)}.topbar{height:72px;display:flex;align-items:center;gap:22px}.brand{display:flex;align-items:center;text-decoration:none;min-width:0}.brand img{display:block;width:auto;height:auto;max-height:38px;max-width:210px;object-fit:contain}.brand strong{font-size:25px;color:var(--navy);letter-spacing:1px}.topbar-tagline{margin:auto;color:var(--muted);font-size:14px;letter-spacing:.07em}.entry-link{display:inline-flex;align-items:center;justify-content:center;min-height:42px;gap:12px;border-radius:7px;background:var(--navy);color:#fff;text-decoration:none;padding:7px 22px;font-weight:700;font-size:14px;white-space:nowrap}.entry-link:hover{background:#116ea8;color:#fff}.desktop-nav{background:var(--navy)}.nav-inner{display:flex;align-items:stretch;justify-content:space-between;gap:10px;min-height:48px}.desktop-nav a{display:flex;align-items:center;padding:9px 12px 6px;min-width:0;border-bottom:3px solid transparent;color:#e9f5fd;text-decoration:none;font-size:14px;white-space:nowrap}.desktop-nav a:hover,.desktop-nav a[aria-current=page]{color:#fff;border-bottom-color:var(--cyan)}.skip-link{position:absolute;z-index:100;left:12px;top:-70px;background:#fff;padding:8px}.skip-link:focus{top:12px}.menu-toggle{display:none;width:40px;height:40px;flex:0 0 40px;border:1px solid var(--line);border-radius:8px;background:#fff;align-items:center;justify-content:center;flex-direction:column;gap:5px;cursor:pointer}.menu-toggle span{width:18px;height:2px;background:var(--navy);display:block}.drawer-backdrop{position:fixed;inset:0;z-index:35;background:rgba(15,34,49,.48);visibility:hidden;opacity:0;pointer-events:none;transition:opacity .2s,visibility .2s}.drawer{position:fixed;z-index:36;left:0;top:0;bottom:0;width:min(86vw,344px);background:#fff;overflow-y:auto;visibility:hidden;transform:translateX(-100%);pointer-events:none;transition:transform .24s,visibility .24s;box-shadow:6px 0 35px #152c3830;padding:20px 22px}.drawer-open .drawer-backdrop{visibility:visible;opacity:1;pointer-events:auto}.drawer-open .drawer{visibility:visible;transform:translateX(0);pointer-events:auto}.drawer-header{display:flex;justify-content:space-between;align-items:center;gap:12px;padding-bottom:16px;border-bottom:1px solid var(--line)}.drawer-header strong{color:var(--navy);font-size:20px}.drawer-header small{display:block;color:var(--muted);font-size:10px;letter-spacing:.1em}.drawer-close{width:42px;height:42px;border:1px solid var(--line);background:#fff;border-radius:8px;color:var(--heading);cursor:pointer;font-size:28px;line-height:1}.drawer-group{padding:13px 0;border-bottom:1px solid var(--line)}.drawer-group h2{font-size:12px;color:var(--muted);margin:5px 0 7px;letter-spacing:.08em}.drawer-group a{display:block;text-decoration:none;padding:9px 8px;color:var(--heading)}.drawer-group a:hover{background:var(--soft)}main{min-height:58vh}.section{margin-block:52px}.section-heading{margin-bottom:24px}.eyebrow{display:block;color:#118ca2;font-weight:700;letter-spacing:.08em;font-size:12px;margin-bottom:8px}h1,h2,h3{color:var(--heading);line-height:1.38;letter-spacing:-.018em}h1{font-size:clamp(28px,3.3vw,42px);line-height:1.34;margin:0 0 20px}h2{font-size:26px;margin:0 0 17px}h3{font-size:20px;margin:0 0 12px}p{margin:0 0 16px}p:last-child{margin-bottom:0}.lead{font-size:17px;line-height:1.85;color:#415b70}.hero{display:grid;grid-template-columns:minmax(0,56fr) minmax(0,44fr);align-items:center;gap:42px;padding:44px 0 34px}.hero p{max-width:610px}.hero-actions{display:flex;flex-wrap:wrap;gap:12px;margin-top:25px}.button-link{display:inline-flex;align-items:center;justify-content:center;border:1px solid var(--navy);background:var(--navy);color:#fff;text-decoration:none;border-radius:7px;min-height:46px;padding:10px 20px;font-weight:700;font-size:14px}.button-link:hover{background:var(--blue);border-color:var(--blue);color:#fff}.button-link--light{background:transparent;color:var(--navy)}.button-link--light:hover{background:var(--soft);color:var(--navy)}.media{display:flex;align-items:center;justify-content:center;width:100%;min-width:0;overflow:hidden;background:var(--soft);border:1px solid var(--line);border-radius:14px}.media img{display:block;width:auto;height:auto;max-width:100%;max-height:100%;object-fit:contain;object-position:center}.media-placeholder{display:block;width:38%;height:36%;border-radius:12px;background:linear-gradient(135deg,#dceef5,#c9e9f0);opacity:.65}.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--wide{height:min(190px,21vw)}.media--portrait{max-width:350px;margin-inline:auto}.shortcut-strip{background:#eaf6fa;border-block:1px solid var(--line)}.shortcut-inner{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:15px;padding-block:17px}.shortcut-inner div{display:flex;flex-wrap:wrap;gap:8px 14px;font-size:13px}.shortcut-inner strong{color:var(--heading)}.shortcut-inner a{color:var(--navy)}.topic-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:14px}.topic-card{padding:22px 20px;background:#fff;border:1px solid var(--line);border-radius:12px;display:flex;flex-direction:column;gap:8px;text-decoration:none;min-width:0}.topic-card:hover,.info-card:hover{border-color:#a3d5e6}.topic-card span{color:#1387a5;font-size:12px;font-weight:700}.topic-card strong{font-size:18px;color:var(--heading)}.topic-card p{font-size:14px;color:var(--muted);line-height:1.7}.editor-grid{display:grid;grid-template-columns:2fr 1fr;gap:18px}.editor-lead{padding:30px;background:var(--navy);border-radius:14px;color:#ebf5ff}.editor-lead h3{color:#fff;font-size:25px}.editor-lead p{color:#e7f2f9}.editor-lead a{color:#fff;font-weight:700}.editor-side{display:grid;gap:16px}.info-card{background:#fff;border:1px solid var(--line);border-radius:12px;padding:23px}.info-card h3{font-size:19px}.info-card p{font-size:15px}.split-feature{display:grid;grid-template-columns:1fr 1fr;gap:38px;align-items:center}.split-feature--reverse .media{order:-1}.split-feature .copy{max-width:540px}.overline{color:#1387a5;font-size:13px;font-weight:700}.rule-grid,.three-col{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}.rule-grid article,.three-col article{background:#fff;border:1px solid var(--line);border-radius:12px;padding:23px}.rule-grid .number,.number{color:#1389a7;font-weight:bold;font-size:14px}.path-steps{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:16px;counter-reset:step}.path-steps li{list-style:none;border-top:2px solid #50bacb;padding:17px 10px 0;position:relative}.path-steps li:before{counter-increment:step;content:'0' counter(step);display:block;color:#168ea7;font-size:14px;font-weight:700;margin-bottom:6px}.path-steps strong{display:block;color:var(--heading)}.path-steps p{font-size:14px}.editor-note{background:var(--soft2);padding:25px 30px;border-left:4px solid var(--cyan);border-radius:8px}.page-intro{padding-top:39px;padding-bottom:18px;max-width:920px}.page-intro h1{font-size:clamp(26px,3vw,36px)}.page-intro p{max-width:790px}.article-width{max-width:780px}.prose h2{margin:34px 0 14px}.prose h3{margin:25px 0 12px}.prose p,.prose li{line-height:1.82}.prose ul,.prose ol{padding-left:23px}.feature-panel{padding:26px;background:#fff;border:1px solid var(--line);border-radius:12px}.feature-panel>h2:first-child{margin-top:0}.table-wrap{overflow-x:auto;width:100%;border:1px solid var(--line);border-radius:11px;background:#fff}table{border-collapse:collapse;width:100%;min-width:540px;font-size:15px}th,td{padding:14px 17px;text-align:left;border-bottom:1px solid var(--line);vertical-align:top}th{background:var(--soft);color:var(--heading);font-weight:700}tr:last-child td{border-bottom:0}.mini-steps{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:14px}.mini-steps article{background:#fff;border-left:3px solid var(--cyan);padding:18px 19px}.mini-steps h3{font-size:18px;margin:6px 0}.article-aside{display:grid;grid-template-columns:minmax(0,760px) minmax(0,240px);gap:38px;align-items:start}.term-sidebar{position:sticky;top:25px;background:var(--soft);border-radius:12px;padding:20px}.term-sidebar dl{margin:0}.term-sidebar dt{font-weight:700;color:var(--heading);margin-top:14px}.term-sidebar dd{margin:0;color:var(--text);font-size:14px}.matrix{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}.matrix article{background:#fff;padding:24px;border:1px solid var(--line);border-radius:12px}.matrix p,.matrix li{font-size:15px}.gallery-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:20px}.gallery-grid figure{margin:0;background:#fff;border:1px solid var(--line);border-radius:12px;overflow:hidden;padding:12px}.gallery-grid figcaption{padding:12px 7px 6px;font-size:14px;line-height:1.7}.gallery-grid figcaption strong{display:block;color:var(--heading);font-size:17px}.toc{display:flex;flex-wrap:wrap;gap:10px;margin:20px 0}.toc a{padding:9px 14px;background:var(--soft);border:1px solid var(--line);text-decoration:none;border-radius:7px;font-size:14px;font-weight:bold}.faq-list{display:grid;gap:10px}.faq-list details{background:#fff;border:1px solid var(--line);border-radius:8px;padding:0 17px}.faq-list summary{cursor:pointer;padding:14px 0;color:var(--heading);font-weight:700}.faq-list details p{border-top:1px solid var(--line);padding:14px 0;font-size:15px}.related-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:15px}.related-link{display:flex;flex-direction:column;gap:7px;min-width:0;text-decoration:none;padding:21px;background:#fff;border:1px solid var(--line);border-radius:12px}.related-link strong{font-size:17px;color:var(--heading)}.related-link span:not(.arrow){font-size:14px;color:var(--muted)}.related-link .arrow{align-self:flex-end;color:var(--blue)}.site-footer{background:var(--footer);color:#EAF7FF;margin-top:70px}.footer-grid{display:grid;grid-template-columns:1fr 1fr;gap:75px;padding-top:44px;padding-bottom:35px}.footer-brand{font-size:22px;font-weight:700;color:#fff}.footer-brand span{font-size:11px;letter-spacing:.09em;margin-left:6px}.site-footer p{max-width:470px;font-size:14px;color:#c9e3f3}.site-footer h2{font-size:16px;color:#fff}.footer-links{display:flex;flex-wrap:wrap;gap:6px 22px}.site-footer a{font-size:14px;color:#eaf7ff}.footer-bottom{border-top:1px solid #426782;padding-block:17px 22px;display:flex;justify-content:space-between;gap:18px;color:#c5dce9;font-size:12px}.bottom-nav{display:none}.back-to-top{position:fixed;right:22px;bottom:25px;width:44px;height:44px;border:0;background:var(--navy);color:#fff;border-radius:8px;font-size:22px;cursor:pointer;opacity:0;visibility:hidden;pointer-events:none;transition:opacity .2s}.back-to-top.is-visible{opacity:1;visibility:visible;pointer-events:auto}@media(max-width:980px){.container{width:calc(100% - 44px)}.topbar{height:63px}.menu-toggle{display:flex}.brand{margin-inline:auto}.brand img{max-height:30px;max-width:175px}.topbar-tagline,.desktop-nav{display:none}.entry-link{min-height:40px;padding:7px 13px;font-size:13px}.hero{gap:24px}.article-aside{grid-template-columns:minmax(0,1fr) 220px;gap:22px}.topic-grid{grid-template-columns:repeat(3,minmax(0,1fr))}.shortcut-inner{grid-template-columns:1fr;gap:7px}}@media(max-width:760px){.hero,.split-feature,.editor-grid,.footer-grid,.article-aside{grid-template-columns:1fr}.hero{padding-top:28px}.hero .media{order:-1}.split-feature--reverse .media{order:0}.term-sidebar{position:static}.topic-grid,.gallery-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.matrix,.rule-grid,.three-col,.related-grid{grid-template-columns:1fr 1fr}.footer-grid{gap:15px}.footer-bottom{flex-direction:column}.path-steps{grid-template-columns:1fr 1fr}}@media(max-width:640px){.container{width:calc(100% - 32px)}body{font-size:15px}.topbar{gap:9px}.brand img{max-height:28px;max-width:130px}.brand strong{font-size:19px}.entry-link{padding:6px 10px;font-size:12px}.entry-link span{display:none}h1{font-size:29px}h2{font-size:22px}h3{font-size:18px}.lead{font-size:15px}.section{margin-block:34px}.page-intro{padding-top:27px}.page-intro h1{font-size:27px}.hero{gap:22px}.hero-actions{gap:9px}.button-link{padding:10px 12px;font-size:13px}.media--hero{height:200px}.media--feature{height:180px}.media--card{height:145px}.media--banner,.media--wide{height:150px}.media--mobile{height:290px;max-width:250px}.topic-grid,.gallery-grid,.rule-grid,.three-col,.matrix,.related-grid{grid-template-columns:1fr}.topic-card{padding:18px}.editor-lead{padding:23px}.info-card{padding:18px}.split-feature{gap:18px}.mini-steps{grid-template-columns:1fr}.path-steps{gap:12px}.footer-grid{padding-top:33px}.footer-bottom{padding-bottom:24px}.bottom-nav{position:fixed;display:grid;grid-template-columns:repeat(4,1fr);left:0;right:0;bottom:0;background:#fff;border-top:1px solid var(--line);z-index:22;padding-bottom:env(safe-area-inset-bottom);box-shadow:0 -2px 12px #12365312}.bottom-nav a{min-height:53px;display:flex;justify-content:center;align-items:center;font-size:13px;text-decoration:none;font-weight:700}.bottom-nav a[aria-current=page]{color:#008da8;border-top:3px solid var(--cyan)}body{padding-bottom:calc(53px + env(safe-area-inset-bottom))}.back-to-top{bottom:calc(70px + env(safe-area-inset-bottom));right:12px;width:40px;height:40px}.editor-note{padding:18px}.feature-panel{padding:18px}}@media(max-height:520px) and (max-width:640px){.bottom-nav{position:static}body{padding-bottom:0}.back-to-top{bottom:15px}}@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*:before,*:after{transition:none!important;animation:none!important}}