:root{color-scheme:light;--paper:#f6f4ef;--surface:#fffefb;--ink:#15253b;--muted:#5e6975;--line:#d9ddd9;--blue:#244fde;--yellow:#f4cd58;--soft:#e9eef8;--warn:#74531b;--warn-bg:#fff3c9;--shadow:0 20px 60px #172b4810;--radius:12px}
:root[data-theme=dark]{color-scheme:dark;--paper:#121b28;--surface:#1a2636;--ink:#edf1f5;--muted:#a8b5c6;--line:#344256;--blue:#9badff;--yellow:#f4cd58;--soft:#23334c;--warn:#f4d78a;--warn-bg:#423923;--shadow:0 20px 60px #0002}
*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:100px}body{margin:0;background:var(--paper);color:var(--ink);font-family:-apple-system,BlinkMacSystemFont,"PingFang SC","Microsoft YaHei",sans-serif;font-size:15px;line-height:1.7}h1,h2,h3,h4,p{margin:0}a{color:inherit;text-decoration:none}button,input,select{font:inherit}button,a,input,select,summary{-webkit-tap-highlight-color:transparent}button,summary{cursor:pointer}button{color:inherit}a:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible,summary:focus-visible,[tabindex]:focus-visible{outline:3px solid var(--blue);outline-offset:4px}a:hover{color:var(--blue)}button:disabled{opacity:.5;cursor:not-allowed}input[type=checkbox]{accent-color:var(--blue);width:17px;height:17px}button{border:1px solid var(--line);background:var(--surface);border-radius:6px;padding:7px 12px}button:hover:not(:disabled){border-color:var(--blue)}[hidden]{display:none!important}.js-only{display:none!important}.js-enabled .js-only{display:initial!important}.js-enabled .article-tools,.js-enabled .practice-columns,.js-enabled .practice-export{display:flex!important}.js-enabled .practice-review{display:grid!important}.js-enabled .reading-progress{display:block!important}.sr-only{position:absolute;width:1px;height:1px;padding:0;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap}.skip{position:fixed;left:20px;top:-80px;z-index:100;background:var(--ink);color:var(--paper);padding:12px 20px;border-radius:6px}.skip:focus{top:10px}.page{width:min(1220px,calc(100% - 96px));margin:0 auto}.eyebrow,.micro{font-size:11px;font-weight:650;letter-spacing:1.6px;color:var(--muted)}.dot{display:inline-block;width:7px;height:7px;border-radius:50%;background:var(--blue);margin-right:8px}.lead{font-size:18px;line-height:1.9;color:var(--muted)}em{font-style:normal;color:var(--blue)}.button{display:inline-flex;align-items:center;justify-content:center;gap:18px;min-height:46px;padding:10px 20px;border:1px solid var(--line);border-radius:7px;font-size:14px;font-weight:600;background:var(--surface);white-space:nowrap;transition:transform .15s,border-color .15s}.button:hover{transform:translateY(-1px);border-color:var(--blue)}.button.blue{background:#244fde;border-color:#244fde;color:#fff}.button.ink{background:var(--ink);border-color:var(--ink);color:var(--paper)}.button.compact{padding:8px 15px;min-height:40px;font-size:12px}.text-link{color:var(--blue);font-size:14px;font-weight:600;display:inline-flex;align-items:center;gap:12px}.text-button{border:0;background:none;text-decoration:underline;text-underline-offset:4px;padding:0}.site-header{position:sticky;top:0;z-index:30;display:flex;align-items:center;justify-content:space-between;gap:26px;padding:18px max(32px,calc((100vw - 1320px)/2));border-bottom:1px solid var(--line);background:var(--paper)}.brand{display:flex;gap:10px;align-items:center;flex-shrink:0}.brand>span{font-size:17px;font-weight:750;letter-spacing:-.5px;line-height:1.3}.brand small{display:block;font-size:9px;letter-spacing:1.2px;color:var(--muted);margin-top:4px}.site-header nav{display:flex;gap:32px;font-size:13px}.site-header nav a[aria-current=page]{color:var(--blue);font-weight:650}.header-tools{display:flex;gap:12px;align-items:center}.theme-button{width:38px;height:38px;border-radius:50%;padding:0;font-size:20px;background:transparent}.site-footer{margin:84px auto 0;padding:32px max(32px,calc((100vw - 1220px)/2));border-top:1px solid var(--line);display:flex;gap:36px;align-items:center;justify-content:space-between}.site-footer b{font-size:14px}.site-footer p,.site-footer small{font-size:11px;color:var(--muted)}.site-footer nav{display:flex;gap:18px;flex-wrap:wrap;font-size:12px}.toast{position:fixed;bottom:24px;left:50%;transform:translateX(-50%);z-index:90;background:var(--ink);color:var(--paper);max-width:calc(100vw - 32px);padding:10px 18px;border-radius:8px;font-size:13px;box-shadow:var(--shadow)}.toast:empty{display:none}
/* The centre: an editorial opening, then a compact task index. */
.learn-hero{padding:72px 0 52px;display:grid;grid-template-columns:1.08fr 1fr;gap:8%;align-items:center}.hero-copy h1{font-size:clamp(42px,4.8vw,66px);line-height:1.28;letter-spacing:-2.8px;margin:24px 0}.hero-copy .lead{font-size:17px}.search-form{margin-top:30px}.search-form>label{display:block;font-size:12px;font-weight:600;margin-bottom:10px}.search-box{display:flex;align-items:center;border:1px solid var(--line);border-radius:9px;background:var(--surface);padding:6px;box-shadow:0 4px 20px #15253b04}.search-box:focus-within{border-color:var(--blue);box-shadow:0 0 0 3px color-mix(in srgb,var(--blue) 12%,transparent)}.search-box>span{font-size:27px;padding:0 10px;color:var(--muted)}.search-box input{min-width:0;width:100%;border:0;background:transparent;padding:10px 4px;outline:none;font-size:13px;color:var(--ink)}.search-box input:focus-visible{outline:none}.search-box button{border:0;background:var(--ink);color:var(--paper);font-size:12px;white-space:nowrap;padding:11px 16px}.search-form>p{display:flex;gap:8px;align-items:center;margin-top:9px;color:var(--muted);font-size:11px}.search-form kbd{margin-left:auto;border:1px solid var(--line);padding:0 7px;border-radius:4px;font-family:inherit}.hero-notebook{display:block;padding:20px 22px 22px;background:#172a44;color:#f6f4ef;border-radius:14px;box-shadow:0 20px 42px #14253e20;transform:rotate(1deg);transition:transform .25s}.hero-notebook:hover{color:#fff;transform:rotate(0)}.notebook-top{display:flex;justify-content:space-between;font-size:10px;letter-spacing:1.5px;margin-bottom:18px;color:#a9bad0}.notebook-paper{padding:30px 27px 24px;background:#fffdf7;color:#15253b;border-radius:5px;transform:rotate(-2deg)}.notebook-paper .micro{color:#647083}.notebook-paper h2{font-size:26px;line-height:1.6;margin:16px 0 22px;letter-spacing:-.8px}.notebook-rule{display:flex;align-items:center;gap:16px;border-top:1px solid #dce1e7;padding-top:12px;font-size:10px;color:#647083}.flow-arrow{color:#244fde;font-size:22px;animation:nudge 3s ease-in-out infinite}.notebook-paper table{width:100%;font-size:13px;margin-top:12px;border-collapse:collapse}.notebook-paper th{text-align:left;font-size:10px;color:#667487;font-weight:500;padding:9px 3px}.notebook-paper td{padding:14px 3px;border-top:1px solid #dce1e7}.notebook-paper s{font-size:11px;color:#8791a0;margin-right:4px}.notebook-paper .attention{background:#fff0bc}.notebook-paper .attention span{font-size:10px;background:#e5bc4b;padding:1px 5px;border-radius:3px}.note-pencil{font-size:12px;color:#5b5c4b;margin-top:16px}.notebook-bottom{display:flex;justify-content:space-between;align-items:center;padding:26px 5px 2px}.notebook-bottom strong{display:block;font-size:17px}.notebook-bottom small{display:block;font-size:10px;color:#bdc9da;margin-top:3px}.circle-arrow{border-radius:50%;background:#f4cd58;color:#15253b;font-size:23px;display:grid;place-items:center;width:43px;height:43px}.section-label{display:flex;align-items:baseline;justify-content:space-between;gap:20px;margin-bottom:20px}.section-label h2{font-size:18px;letter-spacing:-.4px}.section-label>span,.section-label>a{font-size:11px;color:var(--muted)}.route-section{padding:28px 0 55px}.quick-routes{display:grid;grid-template-columns:repeat(3,1fr);border-top:1px solid var(--line);border-bottom:1px solid var(--line)}.quick-routes>a{display:flex;gap:14px;padding:24px 20px 24px 0;align-items:center}.quick-routes>a+a{border-left:1px solid var(--line);padding-left:24px}.route-number{font-size:26px;letter-spacing:-1px;color:var(--blue);font-variant-numeric:tabular-nums}.quick-routes h3{font-size:15px}.quick-routes p{font-size:10px;color:var(--muted);margin-top:4px}.quick-routes>a>b{margin-left:auto;font-size:20px}.library{display:grid;grid-template-columns:240px 1fr;gap:60px;align-items:start;padding:30px 0 64px}.library-nav{position:sticky;top:116px}.library-nav h2{font-size:28px;margin:10px 0 24px}.library-nav h2>span{font-size:11px;font-weight:500;color:var(--muted);margin-left:14px}.library-nav nav a{display:flex;justify-content:space-between;gap:12px;border-bottom:1px solid var(--line);padding:12px 0;font-size:13px}.reading-progress{font-size:11px;color:var(--muted);margin-top:32px}.reading-progress progress{display:block;width:100%;height:5px;margin:8px 0 12px;accent-color:var(--blue)}.reading-progress button{border:0;padding:0;background:none;font-size:11px;color:var(--muted);text-decoration:underline;text-underline-offset:3px}.reading-progress small{display:block;margin-top:7px;font-size:10px}.guide-group{margin-bottom:40px;scroll-margin-top:110px}.group-title{display:flex;justify-content:space-between;gap:16px;align-items:baseline;border-bottom:2px solid var(--ink);padding-bottom:13px}.group-title h3{font-size:17px}.group-title p{font-size:11px;color:var(--muted)}.guide-row{padding:23px 0;display:flex;justify-content:space-between;gap:24px;align-items:center;border-bottom:1px solid var(--line)}.guide-row h4{font-size:16px;font-weight:600}.guide-row p{font-size:12px;color:var(--muted);margin-top:5px;max-width:540px}.read-time{white-space:nowrap;color:var(--muted);font-size:10px}.read-time b{font-size:17px;color:var(--ink);margin-left:12px}.read-mark{font-size:11px;color:var(--blue)}.diagnose{display:grid;grid-template-columns:1fr 1.4fr;gap:10%;padding:50px;background:var(--soft);border-radius:12px}.diagnose h2{font-size:32px;margin:14px 0}.diagnose p{font-size:13px;color:var(--muted)}summary{list-style:none}summary::-webkit-details-marker{display:none}.diagnose details{border-bottom:1px solid color-mix(in srgb,var(--ink) 18%,transparent)}.diagnose summary{font-size:15px;font-weight:600;padding:19px 0;display:flex;justify-content:space-between;gap:20px}.diagnose details a{display:block;padding:4px 0 10px;font-size:12px;color:var(--blue)}.diagnose .text-link{margin-top:23px}.resource-strip{margin-top:64px;display:grid;grid-template-columns:1fr auto;gap:24px;align-items:center}.resource-strip h2{font-size:24px;margin-top:10px}.resource-actions{display:flex;gap:10px}.demo-video{grid-column:1/-1;border-top:1px solid var(--line);border-bottom:1px solid var(--line);margin-top:10px;padding:17px 0}.demo-video summary{display:flex;justify-content:space-between;font-size:13px}.demo-video video{display:block;max-width:800px;width:100%;margin:20px auto 12px;border-radius:8px}.demo-video p{font-size:11px;text-align:center;color:var(--muted)}.search-results{padding:26px 28px;margin-bottom:30px;border:1px solid var(--line);border-radius:10px;background:var(--surface);scroll-margin-top:102px}.search-results h2{font-size:20px}.search-results #searchStatus{font-size:12px;color:var(--muted)}.search-hit{display:block;position:relative;border-bottom:1px solid var(--line);padding:18px 32px 18px 0}.search-hit>span{font-size:10px;color:var(--blue)}.search-hit h3{font-size:16px;margin:3px 0}.search-hit p{font-size:12px;color:var(--muted)}.search-hit>b{position:absolute;right:0;top:35px}.empty-search{padding:24px 0 8px}.empty-search h3{font-size:18px}.empty-search p{font-size:13px;max-width:650px;margin-top:8px}.empty-search a{text-decoration:underline;color:var(--blue)}
/* Reading: persistent library, generous text column, local table of contents. */
.article-layout{display:grid;grid-template-columns:205px minmax(0,1fr) 164px;gap:46px;padding-top:38px}.article-sidebar{position:sticky;top:110px;max-height:calc(100vh - 135px);overflow:auto;padding-right:12px;font-size:12px}.back-link{font-weight:600}.mini-search{display:flex;margin:20px 0;border:1px solid var(--line);border-radius:6px;background:var(--surface);padding:3px}.mini-search input{min-width:0;width:100%;background:transparent;border:0;font-size:12px;padding:6px;color:var(--ink)}.mini-search button{padding:3px 8px;border:0;background:transparent}.article-index>summary{font-size:11px;color:var(--muted);letter-spacing:1px;margin-bottom:16px}.article-index nav p{font-size:10px;color:var(--muted);margin:22px 0 7px}.article-index nav a{display:block;padding:6px 9px;line-height:1.65;margin-left:-9px;border-radius:5px;font-size:11px}.article-index a[aria-current=page]{background:var(--soft);color:var(--blue);font-weight:650}.article-body{min-width:0;padding-bottom:30px}.breadcrumb{display:flex;gap:9px;font-size:11px;color:var(--muted);margin-bottom:24px}.article-header .eyebrow{font-size:10px;letter-spacing:.4px}.article-header h1{font-size:38px;line-height:1.45;letter-spacing:-1.5px;margin:16px 0}.article-header .lead{font-size:15px;line-height:1.95}.article-tools{gap:12px;margin-top:20px}.article-tools button{font-size:11px;padding:5px 10px;border-color:var(--line);background:transparent}.article-section{margin-top:46px;scroll-margin-top:110px}.article-section h2{font-size:22px;letter-spacing:-.6px;margin-bottom:18px;line-height:1.6}.article-section h2 a{display:flex;align-items:baseline;gap:12px;font-size:11px;font-weight:500;color:var(--muted)}.article-section h2 span{font-size:22px;font-weight:650;color:var(--ink)}.article-section h2 i{font-size:15px;color:var(--blue);opacity:0;font-style:normal}.article-section h2 a:hover i,.article-section h2 a:focus-visible i{opacity:1}.article-section>p{font-size:14px;line-height:2;color:var(--muted);margin-top:14px}.steps-list{padding:0;margin:16px 0;list-style:none;counter-reset:steps}.steps-list li{counter-increment:steps;display:flex;gap:16px;padding:12px 0;line-height:1.9;font-size:14px}.steps-list li:before{content:counter(steps);display:grid;place-items:center;border-radius:50%;background:var(--soft);font-size:11px;color:var(--blue);min-width:26px;height:26px;flex-shrink:0;margin-top:2px}.table-scroll{overflow:auto;border:1px solid var(--line);border-radius:8px;margin:20px 0;max-width:100%;background:var(--surface)}.table-scroll table{width:100%;border-collapse:collapse;text-align:left;font-size:12px}.table-scroll th{background:var(--soft);font-size:11px;font-weight:650;white-space:nowrap;padding:13px 14px;color:var(--ink)}.table-scroll td{padding:15px 14px;border-top:1px solid var(--line);min-width:110px;vertical-align:top;color:var(--muted);line-height:1.85}.table-scroll td:first-child{color:var(--ink);font-weight:550}.article-note{border-left:3px solid var(--yellow);background:var(--warn-bg);border-radius:0 6px 6px 0;padding:18px 20px;margin-top:20px;color:var(--warn)}.article-note b{font-size:12px}.article-note p{font-size:12px;line-height:1.95;margin-top:5px}.article-note a{text-decoration:underline}.prompt-block{border:1px solid var(--line);border-radius:8px;background:var(--surface);padding:18px 20px;margin:20px 0}.prompt-block>div{display:flex;align-items:center;justify-content:space-between;gap:10px;font-size:10px;color:var(--muted)}.prompt-block button{font-size:10px;padding:3px 9px}.prompt-block p{font-size:13px;line-height:2;margin-top:13px}.inline-links{display:flex;flex-wrap:wrap;gap:10px 22px;margin-top:20px}.inline-links a{font-size:12px;color:var(--blue);border-bottom:1px solid var(--line);padding-bottom:4px}.toc{position:sticky;top:118px;align-self:start;font-size:11px}.toc nav{border-left:1px solid var(--line);margin:18px 0 28px}.toc nav a{display:block;padding:7px 0 7px 14px;line-height:1.7;border-left:2px solid transparent;margin-left:-1px;color:var(--muted)}.toc nav a[aria-current=location]{border-color:var(--blue);color:var(--blue)}.toc-practice{display:block;padding:15px;border-radius:7px;background:var(--soft);font-size:10px}.toc-practice b{display:block;font-size:12px;margin-top:7px}.toc>.text-link{font-size:11px;margin-top:18px}.completion{border-top:2px solid var(--ink);padding:25px 25px 20px;margin-top:46px;background:var(--surface);scroll-margin-top:110px}.completion h2{font-size:23px;margin:8px 0 16px}.completion ul{list-style:none;padding:0;font-size:13px;line-height:2.2}.completion li{display:flex;gap:12px}.completion li span{color:var(--blue)}.complete-toggle{font-size:12px;cursor:pointer}.complete-toggle input{vertical-align:middle;margin-right:6px}.complete-toggle small{font-size:10px;color:var(--muted);margin-left:6px}.storage-note{font-size:11px;color:var(--warn);margin-top:8px}.next-guides{margin-top:36px}.next-guides h2{font-size:17px;margin-bottom:8px}.next-guides>a{display:flex;justify-content:space-between;gap:15px;border-bottom:1px solid var(--line);padding:14px 0;font-size:13px}.article-cta{margin-top:25px;display:flex;gap:18px;align-items:center}.article-cta .text-link{font-size:12px}
/* FAQ and practice. */
.simple-hero{max-width:710px;padding:64px 0 44px}.simple-hero h1{font-size:50px;line-height:1.35;letter-spacing:-2px;margin:20px 0}.simple-hero .lead{font-size:16px}.faq-layout{display:grid;grid-template-columns:210px minmax(0,1fr);gap:90px}.faq-nav{position:sticky;top:120px;align-self:start}.faq-nav a{display:flex;justify-content:space-between;border-bottom:1px solid var(--line);font-size:13px;padding:12px 0}.faq-group{margin-bottom:40px;scroll-margin-top:110px}.faq-group h2{font-size:19px;border-bottom:2px solid var(--ink);padding-bottom:16px}.faq-item{border-bottom:1px solid var(--line);scroll-margin-top:110px}.faq-item summary{padding:21px 0;display:flex;justify-content:space-between;gap:25px;align-items:center;font-weight:550;font-size:15px}.faq-item summary>span{font-size:20px;font-weight:400;transition:transform .15s}.faq-item[open] summary>span{transform:rotate(45deg)}.faq-item[open],.faq-item:target{background:var(--surface)}.faq-item[open] summary,.faq-item[open] .faq-answer{padding-left:18px;padding-right:18px}.faq-answer{padding:0 0 23px}.faq-answer p{font-size:14px;color:var(--muted);line-height:1.95;margin-bottom:15px}.faq-answer .text-link{font-size:12px}.copy-faq{font-size:10px;margin-left:16px;border:0;background:transparent;color:var(--muted);padding:5px}.faq-end{padding:32px;border-top:1px solid var(--line);margin-top:20px;text-align:center}.faq-end h2{font-size:27px}.faq-end p{font-size:13px;color:var(--muted);margin:10px 0 20px}.faq-end .text-link{margin-left:20px}.practice-header{display:flex;justify-content:space-between;gap:40px;align-items:end;padding:62px 0 36px}.practice-header h1{font-size:46px;line-height:1.4;letter-spacing:-1.8px;margin:16px 0}.practice-header .lead{font-size:15px}.practice-boundary{font-size:12px;border-left:2px solid var(--yellow);padding-left:20px;max-width:340px}.practice-boundary b{font-size:12px}.practice-boundary p{color:var(--muted);font-size:11px;margin:7px 0 12px}.practice-boundary a{color:var(--blue);font-size:11px}.practice-steps{display:flex;gap:40px;border-top:1px solid var(--line);padding:18px 0;margin-bottom:18px;font-size:12px;color:var(--muted)}.practice-steps b{font-size:11px;margin-right:10px;border:1px solid var(--line);border-radius:50%;display:inline-grid;place-items:center;width:30px;height:30px}.practice-steps .done{color:var(--blue)}.practice-steps .done b{background:var(--blue);color:var(--paper);border-color:var(--blue)}.practice-workbench{display:grid;grid-template-columns:320px minmax(0,1fr);border:1px solid var(--line);border-radius:12px;overflow:hidden;box-shadow:var(--shadow);background:var(--surface)}.practice-source{padding:28px 25px;background:var(--soft);border-right:1px solid var(--line)}.practice-source h2{font-size:21px;margin:18px 0 22px;line-height:1.6}.practice-source article{padding:0 0 22px;margin:0 0 22px;border-bottom:1px solid 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