@import url('https://fonts.googleapis.com/css2?family=DM+Sans:wght@400;500;600;700&family=Noto+Sans+SC:wght@400;500;600;700&display=swap');
:root{--bg:#f8f9fc;--panel:#fff;--ink:#1e293b;--strong:#122038;--muted:#728096;--faint:#99a5b5;--line:#e6eaf1;--blue:#4973d6;--blue-lite:#eef3ff;--purple:#8665d9;--green:#159f89;--gold:#d88a41;--sidebar:#131e32;--side-ink:#eef4ff;--shadow:0 8px 38px rgba(30,42,72,.045);--main-width:1100px;color-scheme:light}
:root[data-theme='dark']{--bg:#0f1623;--panel:#182234;--ink:#d7e1ef;--strong:#eef3fd;--muted:#a5b3c6;--faint:#8194ab;--line:#314057;--blue:#8baeff;--blue-lite:#1b2b4c;--shadow:none;--sidebar:#11192a;color-scheme:dark}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--ink);font-family:'DM Sans','Noto Sans SC',-apple-system,BlinkMacSystemFont,'PingFang SC','Microsoft YaHei',sans-serif;font-size:15px;line-height:1.72;-webkit-font-smoothing:antialiased}
button,input{font:inherit}button{cursor:pointer}a{color:var(--blue);text-decoration:none}a:hover{text-decoration:underline}button:focus-visible,a:focus-visible,input:focus-visible{outline:3px solid #6d9bff;outline-offset:3px}
.app-shell{display:grid;grid-template-columns:258px minmax(0,1fr);min-height:100vh}.sidebar{background:var(--sidebar);padding:29px 16px 20px;color:var(--side-ink);display:flex;flex-direction:column;position:sticky;top:0;height:100vh;overflow-y:auto}
.brand{display:flex;gap:12px;align-items:center;padding:3px 10px 32px;cursor:pointer}.brand-icon{width:40px;height:40px;background:#f0f4ff;color:#223762;display:grid;place-items:center;border-radius:12px;font-weight:700;font-size:23px;letter-spacing:-3px}.brand-icon span{color:#608cfa}.brand-name{font-size:16px;font-weight:700;letter-spacing:-.5px}.brand-desc{font-size:11px;color:#8d9fbe;letter-spacing:.5px}.nav-eyebrow{font-size:10px;letter-spacing:2px;color:#8a9ab6;padding:8px 14px;font-weight:700}.course-nav{display:grid;gap:6px}.nav-link{width:100%;padding:13px 11px;border:0;background:none;border-radius:11px;text-align:left;display:flex;align-items:center;gap:11px;color:#b9c8dc;transition:background .18s,color .18s}.nav-link:hover{background:#233653;color:#fff}.nav-link.active{background:#2c3e5a;color:#fff}.nav-symbol{display:grid;place-items:center;width:34px;height:34px;border-radius:10px;background:#293b55;color:#dce5f7;font-size:17px;font-weight:600;flex-shrink:0}.nav-main{min-width:0;flex:1}.nav-main b{font-size:13px;display:block;font-weight:600}.nav-main small{font-size:11px;color:#879bb6;display:block;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.nav-count{font-size:11px;color:#98aec6}.sidebar-bottom{margin-top:auto;padding:24px 12px 4px}.sidebar-note{border-top:1px solid #2b3b53;padding-top:20px;font-size:12px;line-height:1.95;color:#91a3c1}.note-label{color:#d8e6fc;font-weight:700;font-size:12px}.repo-link{margin-top:21px;display:flex;justify-content:space-between;color:#a1b9e6;font-size:12px}.sidebar-loading{font-size:12px;padding:15px;color:#b5c4d7}
.main-frame{min-width:0;display:flex;flex-direction:column}.topbar{height:82px;position:sticky;top:0;z-index:20;border-bottom:1px solid var(--line);background:color-mix(in srgb,var(--bg) 92%,transparent);backdrop-filter:blur(17px);display:flex;align-items:center;justify-content:space-between;gap:18px;padding:0 clamp(24px,4.2vw,68px)}.breadcrumb{font-size:12px;color:var(--muted);letter-spacing:.2px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.breadcrumb span{padding:0 7px;color:var(--faint)}.top-actions{display:flex;align-items:center;gap:11px}.searchbox{border:1px solid var(--line);background:var(--panel);color:var(--muted);border-radius:12px;padding:8px 13px;display:flex;align-items:center;gap:8px;min-width:255px}.search-icon{font-size:21px;line-height:1}.searchbox input{border:0;background:transparent;outline:0;min-width:0;width:170px;color:var(--ink);font-size:12px}.searchbox input::placeholder{color:var(--faint)}.search-shortcut{font-size:10px;color:var(--faint);border:1px solid var(--line);padding:2px 5px;border-radius:5px;white-space:nowrap}.icon-button{width:38px;height:38px;border:1px solid var(--line);border-radius:11px;color:var(--muted);background:var(--panel);font-size:21px}
.main-content{width:min(100%,var(--main-width));padding:clamp(28px,4.5vw,62px) clamp(24px,4.2vw,68px) 80px;margin:0 auto;flex:1}.site-footer{font-size:11px;color:var(--faint);padding:0 25px 24px;text-align:center}.site-footer a{color:var(--muted)}.loading-pane,.empty{border:1px dashed var(--line);border-radius:14px;text-align:center;padding:58px 20px;color:var(--muted);background:var(--panel)}
.eyebrow{color:var(--blue);font-size:11px;letter-spacing:1.65px;font-weight:700;margin-bottom:12px;text-transform:uppercase}.hero h1{font-size:clamp(31px,3.8vw,46px);margin:0 0 16px;color:var(--strong);line-height:1.28;letter-spacing:-1.2px}.hero p{color:var(--muted);margin:0;max-width:720px;line-height:1.9;font-size:14px}.stats{margin:27px 0 0;display:flex;flex-wrap:wrap;gap:11px}.stat{padding:10px 15px;border:1px solid var(--line);border-radius:10px;background:var(--panel);font-size:12px;color:var(--muted)}.stat strong{font-size:17px;color:var(--strong);margin-right:6px;font-variant-numeric:tabular-nums}
.section-title{margin:37px 0 15px;display:flex;align-items:baseline;justify-content:space-between;gap:12px}.section-title h2{font-size:18px;margin:0;font-weight:700;letter-spacing:-.25px;color:var(--strong)}.section-title span{font-size:12px;color:var(--muted)}.course-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:15px}.course-box{border:1px solid var(--line);background:var(--panel);border-radius:16px;padding:23px;text-align:left;color:var(--ink);box-shadow:var(--shadow);transition:transform .2s,border-color .2s}.course-box:hover{transform:translateY(-3px);border-color:#a0b3db}.course-box .course-icon{height:42px;width:42px;display:grid;place-items:center;border-radius:13px;background:color-mix(in srgb,var(--tone) 12%,var(--panel));color:var(--tone);font-size:23px;font-weight:700}.course-box h3{font-size:16px;color:var(--strong);margin:15px 0 5px}.course-box p{font-size:12px;color:var(--muted);margin:0;height:22px}.course-box .course-foot{margin-top:25px;border-top:1px solid var(--line);padding-top:12px;display:flex;justify-content:space-between;color:var(--blue);font-size:12px}
.filters{margin:27px 0 0;display:flex;gap:8px;flex-wrap:wrap}.filter{padding:7px 13px;border-radius:9px;border:1px solid var(--line);background:var(--panel);font-size:12px;color:var(--muted)}.filter.active{color:var(--blue);border-color:color-mix(in srgb,var(--blue) 50%,var(--line));background:var(--blue-lite)}.lesson-list{display:grid;gap:10px}.lesson-row{display:flex;align-items:flex-start;gap:16px;width:100%;text-align:left;border:1px solid var(--line);border-radius:13px;background:var(--panel);padding:17px 19px;box-shadow:var(--shadow);color:var(--ink);transition:transform .18s,border-color .18s}.lesson-row:hover{border-color:#a1b7dd;transform:translateX(2px)}.lesson-no{height:43px;min-width:43px;border-radius:11px;background:var(--blue-lite);color:var(--blue);font-weight:700;display:grid;place-items:center;font-size:14px}.lesson-center{flex:1;min-width:0}.lesson-meta{font-size:11px;color:var(--muted)}.lesson-name{font-size:14px;font-weight:700;margin:4px 0;color:var(--strong)}.lesson-desc{font-size:12px;color:var(--muted);line-height:1.7}.tag{font-size:10px;padding:4px 8px;color:var(--green);border-radius:100px;background:color-mix(in srgb,var(--green) 9%,var(--panel));white-space:nowrap}
.reader{border:1px solid var(--line);border-radius:17px;overflow:hidden;background:var(--panel);box-shadow:var(--shadow)}.reader-head{padding:32px clamp(23px,4vw,48px) 24px;border-bottom:1px solid var(--line)}.back-link{color:var(--blue);border:0;background:none;padding:0;font-size:12px}.reader-head h1{font-size:clamp(25px,3vw,34px);color:var(--strong);margin:9px 0 14px;letter-spacing:-.5px;line-height:1.4}.reader-meta{color:var(--muted);font-size:12px;display:flex;gap:13px;flex-wrap:wrap}.reader-actions{display:flex;gap:9px;flex-wrap:wrap;margin-top:21px}.reader-actions button{background:var(--panel);color:var(--muted);border:1px solid var(--line);padding:7px 12px;border-radius:8px;font-size:12px}.reader-actions button:hover{border-color:var(--blue);color:var(--blue)}.reader-layout{display:grid;grid-template-columns:minmax(0,1fr) 165px;gap:29px;padding:0 clamp(21px,4vw,48px)}.article{min-width:0;padding:18px 0 38px;font-size:14.5px;line-height:2.0;color:var(--ink);word-break:normal;overflow-wrap:break-word}.article h1{display:none}.article h2{font-size:21px;line-height:1.5;margin:37px 0 12px;color:var(--strong);padding-top:18px;border-top:1px solid var(--line)}.article h3{font-size:16px;margin:24px 0 8px;color:var(--strong)}.article p{margin:12px 0}.article blockquote{background:var(--blue-lite);border-left:3px solid var(--blue);padding:11px 17px;margin:17px 0;border-radius:0 8px 8px 0;color:var(--ink)}.article blockquote p{margin:0}.article ol,.article ul{padding-left:24px}.article li{margin:7px 0}.article table{width:100%;display:block;overflow-x:auto;border-collapse:collapse;margin:20px 0;font-size:12.5px}.article th,.article td{border:1px solid var(--line);padding:9px 12px;white-space:nowrap}.article th{background:var(--blue-lite);font-weight:650}.article hr{border:0;border-top:1px solid var(--line);margin:25px 0}.article code:not(pre code){background:var(--blue-lite);color:var(--strong);padding:2px 6px;border-radius:5px;font-size:12px}.article pre{background:#142238;color:#ebf2ff;border-radius:11px;padding:16px;overflow:auto;line-height:1.65}.article pre code{font-family:ui-monospace,'SFMono-Regular',Consolas,monospace;font-size:12px}.article .katex-display{overflow-x:auto;overflow-y:hidden;padding:5px 0 10px;font-size:1.1em}.article strong{color:var(--strong)}.article img,.article svg{max-width:100%}.article a{text-decoration:underline;text-underline-offset:3px}
.toc{padding-top:42px;position:sticky;top:92px;height:max-content;max-height:calc(100vh - 120px);overflow:auto}.toc-title{font-size:10px;letter-spacing:1.6px;color:var(--faint);font-weight:700;margin-bottom:12px}.toc a{display:block;font-size:11px;color:var(--muted);line-height:1.6;padding:5px 0 5px 12px;border-left:2px solid var(--line)}.toc a:hover,.toc a.active{color:var(--blue);border-left-color:var(--blue)}.toc a.sub{padding-left:23px}.reader-pagination{border-top:1px solid var(--line);padding:20px clamp(23px,4vw,48px);display:flex;gap:12px;justify-content:space-between}.reader-pagination button{background:var(--panel);border:1px solid var(--line);border-radius:9px;padding:9px 13px;color:var(--blue);font-size:12px;max-width:49%}.reader-pagination button:disabled{opacity:.4;cursor:default}
/* Animated, accessible concept visuals */
.diagram{margin:25px 0 30px;padding:19px;border:1px solid color-mix(in srgb,var(--blue) 22%,var(--line));background:color-mix(in srgb,var(--blue) 3%,var(--panel));border-radius:15px;overflow:hidden}.diagram-top{display:flex;justify-content:space-between;gap:12px;align-items:center;margin-bottom:5px}.diagram-eyebrow{color:var(--blue);font-size:10px;letter-spacing:1.4px;font-weight:700}.diagram h3{font-size:15px;margin:5px 0 0;color:var(--strong)}.diagram svg{width:100%;height:auto;display:block;max-height:290px}.diagram-scene{position:relative;overflow:hidden}.diagram-caption{font-size:12px;min-height:35px;line-height:1.65;color:var(--muted);margin-top:9px}.diagram-controls{display:flex;align-items:center;gap:8px;flex-wrap:wrap;padding-top:13px;border-top:1px solid var(--line)}.diagram-controls button{border:1px solid var(--line);background:var(--panel);color:var(--blue);font-size:12px;padding:5px 12px;border-radius:8px}.diagram-progress{color:var(--faint);font-size:11px;margin-left:auto;font-variant-numeric:tabular-nums}.diagram input[type=range]{accent-color:var(--blue);max-width:135px}.diagram svg text{font-family:inherit}.diagram .guide{stroke:#c2d0e4;stroke-width:1}.diagram .active-cell{filter:drop-shadow(0 2px 6px rgba(71,110,209,.26))}
.notice{padding:14px 18px;border:1px solid var(--line);background:var(--panel);border-radius:12px;margin-top:26px;color:var(--muted);font-size:12px;line-height:1.85}.notice strong{color:var(--strong)}
@media(max-width:1080px){.reader-layout{grid-template-columns:1fr}.toc{display:none}}
@media(max-width:940px){.app-shell{grid-template-columns:1fr}.sidebar{height:auto;position:relative;padding:9px 12px;display:flex;align-items:center;gap:14px;flex-direction:row;overflow-x:auto;white-space:nowrap}.brand{padding:0;min-width:180px}.brand-icon{width:33px;height:33px;border-radius:10px;font-size:20px}.brand-name{font-size:13px}.brand-desc{font-size:10px}.nav-eyebrow,.sidebar-bottom{display:none}.course-nav{display:flex;gap:3px}.nav-link{padding:8px 10px;margin:0;width:auto}.nav-symbol{display:none}.nav-main b{font-size:12px}.nav-main small,.nav-count{display:none}.topbar{height:67px}}
@media(max-width:600px){.topbar{padding:0 16px}.breadcrumb{max-width:33vw}.searchbox{min-width:unset;padding:8px;width:45vw}.searchbox input{width:100%}.search-shortcut{display:none}.top-actions{gap:6px}.icon-button{width:34px;height:34px}.main-content{padding:27px 16px 53px}.course-grid{grid-template-columns:1fr}.hero h1{font-size:29px}.reader-head{padding:23px 21px}.reader-layout{padding:0 19px}.article{font-size:14px;line-height:1.9}.reader-pagination{padding:18px}.lesson-row{padding:14px;gap:11px}.lesson-no{height:36px;min-width:36px}.tag{display:none}.diagram{padding:12px}.diagram svg{max-height:250px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*::before,*::after{animation-duration:.001ms!important;transition-duration:.001ms!important;scroll-behavior:auto!important}}
.lesson-meta,.lesson-name,.lesson-desc{display:block}

/* Mermaid flow diagrams for future lessons: subtle animated arrows. */
.article .mermaid{margin:22px 0;padding:15px;background:var(--panel);border:1px solid var(--line);border-radius:12px;overflow:auto;text-align:center}
.article .mermaid svg{max-width:100%;height:auto}
.article .mermaid .edgePaths path{stroke-dasharray:8 6;animation:atlas-arrow-flow 6s linear infinite}
@keyframes atlas-arrow-flow{to{stroke-dashoffset:-70}}

/* Progressive four-level learning checks: objective auto-grading + explicit open-ended self-evaluation. */
.quiz-container{border-top:1px solid var(--line);padding:29px clamp(20px,4vw,47px) 36px;background:color-mix(in srgb,var(--blue) 1.5%,var(--panel));scroll-margin-top:95px}
.quiz-head{margin-bottom:24px}.quiz-eyebrow{font-size:10px;font-weight:700;letter-spacing:1.5px;color:var(--blue)}.quiz-head h2{font-size:22px;line-height:1.4;color:var(--strong);margin:9px 0}.quiz-head p{color:var(--muted);font-size:13px;line-height:1.8;max-width:680px;margin:0 0 18px}
.quiz-weight-line{display:grid;grid-template-columns:15fr 20fr 25fr 40fr;border-radius:9px;overflow:hidden;background:var(--line);gap:2px}.quiz-weight-line span{padding:7px 5px;text-align:center;background:color-mix(in srgb,var(--blue) 11%,var(--panel));font-size:10px;color:var(--blue);font-weight:700;white-space:nowrap}
.quiz-question{display:block;border:1px solid var(--line);background:var(--panel);border-radius:12px;padding:15px 18px 19px;margin:0 0 16px;min-width:0}.quiz-question legend{padding:0 8px;display:flex;gap:8px;align-items:center;font-size:12px;color:var(--muted)}.quiz-level{color:var(--blue);font-size:11px;font-weight:800;letter-spacing:.7px}.quiz-question[data-level='4'] .quiz-level{color:#a76c32}.quiz-points{color:var(--muted);font-size:11px}.quiz-prompt{font-size:14px;color:var(--strong);line-height:1.85;margin:8px 0 15px}.quiz-options{display:grid;gap:9px}.quiz-option{display:flex;gap:10px;align-items:flex-start;cursor:pointer;border:1px solid var(--line);border-radius:9px;padding:10px 12px;font-size:13px;line-height:1.6;color:var(--ink)}.quiz-option:has(input:checked){border-color:color-mix(in srgb,var(--blue) 52%,var(--line));background:var(--blue-lite)}.quiz-option input{margin:3px 2px 0 0;accent-color:var(--blue);flex-shrink:0}.quiz-option:has(input:disabled){cursor:default}.quiz-choice{font-weight:700;color:var(--blue);font-size:12px}
.quiz-number-label,.quiz-answer-label{display:flex;flex-direction:column;gap:7px;color:var(--muted);font-size:12px}.quiz-number-label input,.quiz-answer-label textarea,.quiz-self-score select{font:inherit;color:var(--ink);border:1px solid var(--line);border-radius:9px;padding:10px 12px;background:var(--panel);width:100%;max-width:390px}.quiz-answer-label textarea{max-width:none;resize:vertical;min-height:118px;font-size:13px;line-height:1.65}.quiz-number-label span{color:var(--faint)}.quiz-number-label input:disabled,.quiz-answer-label textarea:disabled{opacity:.8}
.quiz-hint{font-size:12px;color:var(--muted);margin-top:13px}.quiz-hint summary{cursor:pointer;color:var(--blue);list-style:inside}.quiz-hint p{line-height:1.7;margin:8px 0 0;padding:10px 12px;background:var(--blue-lite);border-radius:9px}.quiz-feedback{margin:16px 0 0;padding:13px 15px;border-radius:9px;border:1px solid var(--line);font-size:12px;line-height:1.85;color:var(--ink);background:var(--bg)}.quiz-feedback strong{font-size:13px;color:var(--strong)}.quiz-feedback.correct{border-color:color-mix(in srgb,var(--green) 40%,var(--line))}.quiz-feedback.incorrect{border-color:color-mix(in srgb,var(--gold) 55%,var(--line))}.quiz-feedback p{margin:8px 0 0;overflow-wrap:anywhere}.quiz-feedback ol{padding-left:23px;margin:8px 0}.quiz-feedback li{margin:6px 0}.quiz-feedback details{padding:10px;border:1px solid var(--line);border-radius:9px;margin-top:10px;background:var(--panel)}.quiz-feedback summary{cursor:pointer;color:var(--blue)}.quiz-self-score{display:flex;align-items:center;gap:8px;font-weight:600;margin-top:12px;flex-wrap:wrap}.quiz-self-score select{max-width:150px;padding:7px 10px}
.quiz-bottom{margin-top:15px;border-radius:12px;padding:17px 19px;background:var(--blue-lite);border:1px solid var(--line)}.quiz-summary{display:grid;gap:3px}.quiz-summary strong{font-size:14px;color:var(--strong)}.quiz-summary span,.quiz-summary small{font-size:12px;color:var(--muted);line-height:1.6}.quiz-buttons{display:flex;flex-wrap:wrap;gap:9px;margin-top:14px}.quiz-buttons button{border:1px solid var(--line);border-radius:9px;padding:9px 13px;color:var(--blue);background:var(--panel);font-size:12px}.quiz-buttons button.quiz-primary{border-color:var(--blue);background:var(--blue);color:#fff;font-weight:700}.quiz-privacy{font-size:11px;color:var(--muted);margin:14px 0 0;line-height:1.8}.quiz-loading{padding:20px;text-align:center;color:var(--muted);font-size:12px;border:1px dashed var(--line);border-radius:12px}
@media(max-width:600px){.quiz-container{padding:21px 16px 29px}.quiz-head h2{font-size:19px}.quiz-weight-line span{font-size:9px;padding:6px 2px}.quiz-question{padding:13px}.quiz-option{padding:9px}.quiz-prompt{font-size:13px}}