:root{--bg:#f5f1e8;--surface:#fffdf8;--surface2:#f0ece3;--text:#10213a;--muted:#667085;--line:#ded8ca;--blue:#2157d5;--blue2:#6fa1ff;--gold:#ae8a43;--teal:#2f8f88;--shadow:0 20px 50px rgba(26,38,62,.10);--radius:24px}html[data-theme="dark"]{--bg:#07101d;--surface:#0c1728;--surface2:#111d30;--text:#f2f5fb;--muted:#9ba7bb;--line:#223149;--blue:#6b9cff;--blue2:#97b8ff;--gold:#c8a15d;--teal:#5eb8b1;--shadow:0 22px 60px rgba(0,0,0,.36)}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:radial-gradient(circle at 82% 4%,rgba(70,112,210,.08),transparent 28%),var(--bg);color:var(--text);font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;transition:.25s}a{color:inherit;text-decoration:none}.topbar{height:82px;padding:0 clamp(20px,5vw,72px);display:flex;align-items:center;gap:36px;border-bottom:1px solid color-mix(in srgb,var(--line) 70%,transparent);position:sticky;top:0;background:color-mix(in srgb,var(--bg) 88%,transparent);backdrop-filter:blur(18px);z-index:20}.brand{display:flex;align-items:center;gap:12px;min-width:220px}.brand-mark{width:36px;height:34px;position:relative;display:inline-block}.brand-mark:before,.brand-mark:after{content:"";position:absolute;bottom:3px;border-left:18px solid transparent;border-right:18px solid transparent}.brand-mark:before{border-bottom:30px solid var(--gold);left:0;transform:scale(.86)}.brand-mark:after{border-bottom:22px solid var(--surface);left:0;bottom:3px;transform:scale(.64)}.brand-copy{font-family:Georgia,"Times New Roman",serif;font-size:23px;letter-spacing:.16em;line-height:.82}.brand-copy small{display:block;font-family:Inter,sans-serif;font-size:9px;letter-spacing:.28em;color:var(--blue);margin-top:8px}nav{display:flex;gap:28px;flex:1;justify-content:center}nav a{font-size:14px;color:var(--muted);padding:30px 0;position:relative}nav a.active{color:var(--text)}nav a.active:after{content:"";position:absolute;left:0;right:0;bottom:18px;height:2px;background:var(--blue);border-radius:2px}.actions{display:flex;gap:10px}.actions button{border:1px solid var(--line);background:var(--surface);color:var(--text);height:38px;padding:0 13px;border-radius:12px;cursor:pointer}.actions .lang span{color:var(--line);padding:0 5px}main{max-width:1480px;margin:auto;padding:0 clamp(20px,5vw,72px) 72px}.hero{min-height:430px;display:grid;grid-template-columns:1.03fr .97fr;align-items:center;gap:36px}.eyebrow,.mini{font-size:11px;font-weight:800;letter-spacing:.22em;color:var(--blue)}h1{font-family:Georgia,"Times New Roman",serif;font-size:clamp(46px,5.4vw,78px);line-height:.99;letter-spacing:-.04em;margin:18px 0 22px;max-width:760px}h1 span{color:var(--blue)}.hero p{font-size:18px;color:var(--muted)}.hero-art{height:340px;position:relative;perspective:1000px}.glass-scene{position:absolute;inset:35px 30px;transform:rotateX(3deg) rotateY(-8deg)}.glass-base{position:absolute;width:72%;height:42%;left:14%;bottom:10%;border-radius:50%;background:radial-gradient(ellipse,rgba(48,93,186,.28),transparent 65%);filter:blur(7px)}.glass-panel{position:absolute;border:1px solid color-mix(in srgb,var(--blue) 30%,var(--line));border-radius:22px;box-shadow:0 28px 60px rgba(28,75,166,.14),inset 0 1px rgba(255,255,255,.35);backdrop-filter:blur(4px)}.glass-panel.a{width:47%;height:55%;left:5%;top:24%;transform:rotate(-8deg);background:linear-gradient(150deg,color-mix(in srgb,var(--surface) 82%,transparent),color-mix(in srgb,var(--blue) 7%,transparent))}.glass-panel.b{width:52%;height:62%;right:4%;top:8%;transform:rotate(8deg);background:linear-gradient(145deg,color-mix(in srgb,var(--blue) 52%,transparent),color-mix(in srgb,var(--surface) 68%,transparent))}.glass-panel.c{width:43%;height:40%;left:31%;bottom:2%;transform:rotate(1deg);background:linear-gradient(145deg,color-mix(in srgb,var(--surface) 76%,transparent),color-mix(in srgb,var(--gold) 8%,transparent))}.glass-panel:after{content:"f(x) = ax + b";position:absolute;right:12%;top:18%;font-family:Georgia,serif;font-size:20px;color:color-mix(in srgb,var(--text) 65%,transparent)}.curriculum{display:grid;grid-template-columns:330px 1fr;gap:22px;align-items:start}.subject-list,.tree-panel,.features,.coming-card,.lesson-card{border:1px solid var(--line);background:color-mix(in srgb,var(--surface) 94%,transparent);box-shadow:var(--shadow);border-radius:var(--radius)}.subject-list{padding:12px;position:sticky;top:102px}.subject-btn{width:100%;border:0;background:transparent;color:var(--text);display:grid;grid-template-columns:44px 1fr auto;gap:13px;align-items:center;padding:17px 14px;border-radius:16px;text-align:left;cursor:pointer;margin:3px 0}.subject-btn:hover{background:var(--surface2)}.subject-btn.active{background:color-mix(in srgb,var(--blue) 10%,var(--surface));outline:1px solid color-mix(in srgb,var(--blue) 38%,transparent)}.subject-icon{width:44px;height:44px;border-radius:12px;display:grid;place-items:center;font-weight:800;background:var(--surface2);color:var(--blue)}.subject-btn:nth-child(2) .subject-icon{color:#765ec6}.subject-btn:nth-child(3) .subject-icon{color:var(--gold)}.subject-btn:nth-child(4) .subject-icon{color:var(--teal)}.subject-name small{display:block;color:var(--muted);font-size:11px;margin-bottom:4px}.tree-panel{padding:28px}.tree-head{display:flex;justify-content:space-between;align-items:end;margin-bottom:20px}.tree-head h2{font-family:Georgia,serif;font-size:32px;margin:6px 0 0}.count{color:var(--muted);font-size:13px}.tree-section{border-top:1px solid var(--line)}.tree-section:first-child{border-top:0}.section-toggle,.group-toggle{width:100%;border:0;background:transparent;color:var(--text);display:flex;justify-content:space-between;align-items:center;padding:18px 5px;font-size:15px;font-weight:700;cursor:pointer}.section-body{display:none;padding:0 0 14px 22px}.tree-section.open>.section-body,.group.open>.section-body{display:block}.leaf{border-left:1px solid var(--line);padding:11px 0 11px 18px;position:relative}.leaf:before{content:"";position:absolute;width:7px;height:7px;background:var(--blue);border-radius:50%;left:-4px;top:19px}.leaf-title{font-size:14px;font-weight:650;margin-bottom:9px}.leaf-actions{display:flex;flex-wrap:wrap;gap:7px}.leaf-actions a{font-size:11px;padding:7px 9px;border:1px solid var(--line);border-radius:9px;color:var(--muted)}.leaf-actions a:hover{border-color:var(--blue);color:var(--blue)}.group{margin-left:4px;border-left:1px dashed var(--line);padding-left:16px}.group-toggle{font-size:13px;padding:13px 4px}.chev{color:var(--muted);transition:.2s}.open>.section-toggle .chev,.open>.group-toggle .chev{transform:rotate(180deg)}.features{margin-top:28px;padding:24px;display:grid;grid-template-columns:repeat(4,1fr);gap:0}.features>div{padding:7px 24px;border-right:1px solid var(--line)}.features>div:last-child{border-right:0}.features b{display:block;font-family:Georgia,serif;font-size:16px;margin-bottom:7px}.features span{font-size:12px;color:var(--muted)}.page-shell{min-height:calc(100vh - 82px);display:grid;place-items:center;padding:44px 20px}.coming-card{width:min(760px,100%);padding:46px;text-align:center}.lesson-card{width:min(1040px,100%);padding:44px 56px}.lesson-card>.crumb,.lesson-card>.page-type,.lesson-card>.lesson-title,.lesson-card>.subject-label{text-align:center}.crumb{font-size:12px;color:var(--muted);margin-bottom:22px}.page-type{font-size:12px;font-weight:800;letter-spacing:.18em;color:var(--blue);text-transform:uppercase}.lesson-title{font-family:Georgia,serif;font-size:26px;margin:10px 0 4px}.lesson-card>.lesson-title{font-size:clamp(34px,4vw,52px);letter-spacing:-.025em;margin-top:12px}.subject-label{color:var(--gold);font-size:13px;font-weight:700}.soon{margin:30px auto 18px;display:inline-block;padding:8px 14px;border:1px solid color-mix(in srgb,var(--blue) 30%,var(--line));background:color-mix(in srgb,var(--blue) 8%,var(--surface));color:var(--blue);border-radius:999px;font-weight:800;letter-spacing:.1em}.release{display:grid;grid-template-columns:1fr 1fr;gap:12px;max-width:430px;margin:0 auto 28px}.release div{background:var(--surface2);border-radius:14px;padding:15px}.release small{display:block;color:var(--muted);font-size:10px;text-transform:uppercase;letter-spacing:.1em;margin-bottom:5px}.release strong{font-size:15px}.back{display:inline-flex;padding:11px 16px;border-radius:12px;background:var(--text);color:var(--bg);font-size:13px;font-weight:700}.lesson-card>.back{margin-top:34px}.video-note{color:var(--muted);max-width:500px;margin:20px auto 30px;line-height:1.6}.lesson-content{margin-top:42px;text-align:left}.lesson-section{padding:38px 0;border-top:1px solid var(--line)}.lesson-section:first-child{border-top:0}.section-kicker{display:block;font-size:10px;font-weight:800;letter-spacing:.18em;color:var(--blue);margin-bottom:12px}.lesson-section h2{font-family:Georgia,"Times New Roman",serif;font-size:clamp(26px,3vw,38px);line-height:1.12;letter-spacing:-.025em;margin:0 0 15px}.lesson-section h3{font-family:Georgia,"Times New Roman",serif;font-size:20px;margin:0 0 8px}.lesson-section p{color:var(--muted);font-size:16px;line-height:1.75;margin:0 0 18px}.equation-callout{display:flex;align-items:center;justify-content:center;gap:22px;padding:24px;border:1px solid color-mix(in srgb,var(--blue) 28%,var(--line));background:linear-gradient(135deg,color-mix(in srgb,var(--blue) 7%,var(--surface)),var(--surface2));border-radius:18px;font-family:Georgia,serif;font-size:27px}.equation-callout strong{color:var(--blue)}.equation-arrow{color:var(--gold)}.rule-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:12px}.rule-grid>div,.definition-grid>div,.quick-grid>div{border:1px solid var(--line);background:var(--surface2);border-radius:16px;padding:18px}.rule-grid small,.quick-grid small{display:block;color:var(--muted);font-size:10px;text-transform:uppercase;letter-spacing:.12em}.rule-grid strong{display:block;font-family:Georgia,serif;font-size:26px;margin:8px 0}.rule-grid span{font-size:12px;color:var(--muted)}.definition-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:14px}.lesson-content code{display:block;font-family:"SFMono-Regular",Consolas,monospace;color:var(--text);font-size:16px;line-height:1.6;background:color-mix(in srgb,var(--blue) 6%,var(--surface));border:1px solid color-mix(in srgb,var(--blue) 16%,var(--line));padding:10px 13px;border-radius:10px;margin-top:10px}.core-rule{text-align:center}.big-rule{display:inline-block;margin-top:10px;padding:14px 20px;border-radius:12px;background:var(--text);color:var(--bg);font-weight:900;letter-spacing:.12em}.pattern-list{display:grid;gap:10px}.pattern-list>div{display:grid;grid-template-columns:48px 1fr;gap:14px;align-items:center;padding:15px;border:1px solid var(--line);border-radius:14px}.pattern-list>div>span{width:42px;height:42px;border-radius:12px;background:color-mix(in srgb,var(--blue) 10%,var(--surface));color:var(--blue);display:grid;place-items:center;font-weight:800}.pattern-list b{display:block}.pattern-list code{margin-top:6px}.steps{display:grid;gap:14px;padding:0;margin:22px 0;counter-reset:step;list-style:none}.steps li{padding:18px;border-left:3px solid var(--blue);background:var(--surface2);border-radius:0 14px 14px 0}.steps li b,.steps li span{display:block}.steps li span{color:var(--muted);font-size:14px;margin-top:4px}.check-box{display:flex;justify-content:space-between;gap:16px;padding:14px 16px;border-radius:12px;background:color-mix(in srgb,var(--teal) 10%,var(--surface));border:1px solid color-mix(in srgb,var(--teal) 28%,var(--line))}.check-box span{color:var(--teal);font-weight:800}.solution-stack{display:grid;gap:10px;margin:18px 0}.solution-stack code{margin:0;font-size:18px}.tip-line{padding:16px 18px;border-left:3px solid var(--gold);background:color-mix(in srgb,var(--gold) 8%,var(--surface));border-radius:0 12px 12px 0}.sat-note{padding:18px;border-radius:14px;background:color-mix(in srgb,var(--blue) 8%,var(--surface));border:1px solid color-mix(in srgb,var(--blue) 25%,var(--line))}.sat-note b{color:var(--blue)}.sat-note p{margin:6px 0 0}.mistake-list{display:grid;grid-template-columns:1fr 1fr;gap:14px}.mistake-list>div{padding:18px;border:1px solid var(--line);border-radius:14px}.mistake-list>div b{display:block;margin-bottom:7px}.mistake-list>div p{font-size:14px;margin:0}.sat-strategy{background:linear-gradient(135deg,color-mix(in srgb,var(--blue) 6%,transparent),transparent);border-radius:18px;padding-left:24px;padding-right:24px}.quick-grid{display:grid;grid-template-columns:repeat(5,1fr);gap:10px}.quick-grid code{margin-top:7px;padding:0;border:0;background:transparent;font-size:14px}.answer-reveal{margin-top:16px;border:1px solid var(--line);border-radius:12px;padding:14px 16px;background:var(--surface2)}.answer-reveal summary{cursor:pointer;font-weight:800;color:var(--blue)}.answer-reveal p{margin:12px 0 0}.recap-list{padding-left:22px;color:var(--muted);line-height:1.8}.formula-row{display:grid;grid-template-columns:repeat(4,1fr);gap:10px}.formula-row code{margin:0;text-align:center}.next-links{display:grid;grid-template-columns:repeat(2,1fr);gap:12px}.next-links a{padding:18px;border:1px solid var(--line);border-radius:14px;font-weight:800;transition:.2s}.next-links a:hover{border-color:var(--blue);transform:translateY(-2px)}.next-links span{display:block;color:var(--muted);font-size:12px;font-weight:500;margin-top:5px}@media(max-width:900px){.topbar{height:auto;min-height:72px;padding:14px 20px;gap:12px}.brand{min-width:auto;flex:1}.brand-copy{font-size:18px}.topbar nav{display:none}.hero{grid-template-columns:1fr;min-height:650px;padding-top:40px}.hero-art{height:270px}.curriculum{grid-template-columns:1fr}.subject-list{position:static;display:grid;grid-template-columns:repeat(2,1fr)}.tree-panel{padding:20px}.features{grid-template-columns:1fr 1fr}.features>div{border-right:0;border-bottom:1px solid var(--line)}.lesson-card{padding:34px 28px}.rule-grid{grid-template-columns:repeat(2,1fr)}.quick-grid{grid-template-columns:repeat(2,1fr)}.formula-row{grid-template-columns:repeat(2,1fr)}}@media(max-width:560px){main{padding-left:14px;padding-right:14px}.topbar{padding:11px 14px}.actions .lang{display:none}.hero{min-height:570px}.hero h1{font-size:44px}.hero-art{height:220px}.subject-list{grid-template-columns:1fr}.subject-btn{padding:11px}.tree-panel{border-radius:18px;padding:16px}.tree-head h2{font-size:27px}.leaf-actions a{font-size:10px}.features{grid-template-columns:1fr}.coming-card{padding:28px 18px}.release{grid-template-columns:1fr}.lesson-card{padding:28px 18px}.lesson-content{margin-top:32px}.lesson-section{padding:30px 0}.definition-grid,.mistake-list,.next-links{grid-template-columns:1fr}.rule-grid{grid-template-columns:1fr 1fr}.equation-callout{font-size:21px;gap:12px;padding:18px}.quick-grid{grid-template-columns:1fr}.formula-row{grid-template-columns:1fr 1fr}.check-box{flex-direction:column}}
.lesson-content-status{display:flex;align-items:center;gap:7px;margin:10px 0 4px;padding:9px 11px;border-radius:12px;font-size:12px;font-weight:800;line-height:1.25;border:1px solid var(--line,#d8dee8);background:var(--card,#fff);color:var(--muted,#617083)}.lesson-content-status.ready{color:#147a46;border-color:rgba(20,122,70,.25);background:rgba(20,122,70,.08)}.lesson-content-status.scheduled{color:#805b12;border-color:rgba(128,91,18,.24);background:rgba(199,150,42,.10)}.lesson-content-status .dot{width:8px;height:8px;border-radius:50%;background:currentColor;display:inline-block;flex:0 0 auto}.lesson-content-status b{font-weight:900}.lesson-content-status small{font-size:11px;font-weight:700;opacity:.78;margin-left:auto}@media(max-width:700px){.lesson-content-status{width:100%;box-sizing:border-box}.lesson-content-status.scheduled{align-items:flex-start;flex-wrap:wrap}.lesson-content-status small{display:block;width:100%;margin-left:15px}}