:root{--ink:#1b2a4a;--ink-soft:#2e3f63;--paper:#fbf9f4;--paper-dim:#f1eee5;--marigold:#e8a33d;--marigold-deep:#c9821f;--slate:#55606e;--leaf:#3f7856;--brick:#b4532a;--physics:#2f5d8a;--line:#dcd6c6}*{box-sizing:border-box}body{background:var(--paper);color:var(--ink);-webkit-font-smoothing:antialiased;margin:0;font-family:IBM Plex Sans,sans-serif;line-height:1.55}h1,h2,h3{color:var(--ink);margin:0;font-family:Lora,serif;font-weight:600}a{color:inherit;text-decoration:none}.wrap{max-width:1100px;margin:0 auto;padding:0 28px}nav{z-index:40;background:var(--paper);border-bottom:1px solid var(--line);position:sticky;top:0}.breadcrumb-bar-sticky{z-index:30;position:sticky;top:59px}.breadcrumb{color:var(--slate);flex-wrap:wrap;align-items:center;gap:1px;padding:10px 0;font-size:.8rem;display:flex}.breadcrumb-item{align-items:center;display:inline-flex}.breadcrumb a{color:var(--slate);border-radius:5px;padding:3px 7px;text-decoration:none;transition:background .15s,color .15s}.breadcrumb a:hover{color:var(--ink);background:#fff}.breadcrumb-current{color:var(--paper);background:var(--ink);border-radius:20px;margin-left:2px;padding:3px 10px;font-size:.74rem;font-weight:600}.breadcrumb-sep{color:var(--slate);opacity:.5;margin:0 2px;font-size:.85rem}.sticky-header{z-index:25;background:var(--paper);position:sticky;top:59px}.section-divider-sticky{top:calc(59px + var(--sticky-header-h,140px));z-index:20;position:sticky}.nav-inner{justify-content:space-between;align-items:center;max-width:1100px;margin:0 auto;padding:16px 28px;display:flex}.logo{align-items:center;gap:8px;font-family:Lora,serif;font-size:1.35rem;font-weight:700;display:flex}.logo-icon{width:26px;height:26px;display:block}.nav-links{color:var(--slate);gap:32px;font-size:.95rem;display:flex}.nav-links a:hover{color:var(--ink)}.nav-cta{color:var(--paper);background:linear-gradient(135deg,#1b2a4a,#2f5d8a);border-radius:3px;padding:9px 18px;font-size:.9rem;font-weight:600}.nav-cta:hover{filter:brightness(1.15)}@media (max-width:720px){.nav-links{display:none}}.hero{color:var(--paper);text-align:center;background:linear-gradient(135deg,#1b2a4a 0%,#2f5d8a 55%,#3f7856 100%);padding:72px 0 56px}.hero-eyebrow{color:var(--marigold);letter-spacing:.02em;margin-bottom:16px;font-size:.92rem;font-weight:600}.hero h1{color:var(--paper);max-width:640px;margin:0 auto;font-size:2.5rem;line-height:1.2}.hero p.lede{color:#c8cfe0;max-width:480px;margin:18px auto 0;font-size:1.05rem}.hero-price{color:#c8cfe0;background:linear-gradient(135deg,#ffffff29,#ffffff0d);border-radius:30px;align-items:baseline;gap:8px;margin-top:28px;padding:10px 20px;font-size:.92rem;display:inline-flex}.hero-price b{color:var(--marigold);font-family:Lora,serif;font-size:1.15rem}section{padding:64px 0}.section-head{text-align:center;max-width:600px;margin:0 auto 40px}.section-head h2{font-size:1.85rem}.section-head p{color:var(--slate);margin-top:12px;font-size:1rem}.class-grid{grid-template-columns:repeat(4,1fr);gap:18px;display:grid}.class-grid>a{height:100%;display:block}@media (max-width:960px){.class-grid{grid-template-columns:repeat(2,1fr)}}@media (max-width:560px){.class-grid{grid-template-columns:1fr}}.class-card-link{height:100%;display:block}.class-card{border:1px solid var(--line);background:var(--paper);border-radius:8px;flex-direction:column;height:100%;padding:26px 22px 22px;transition:border-color .18s,transform .18s,box-shadow .18s;display:flex;position:relative;overflow:hidden}.class-card-link:hover .class-card{border-color:var(--ink);transform:translateY(-4px)scale(1.035);box-shadow:0 14px 28px #1b2a4a24}.class-card .bar{width:5px;position:absolute;top:0;bottom:0;left:0}.class-num{color:var(--ink);font-family:Lora,serif;font-size:2.6rem;font-weight:700;line-height:1}.class-num span{color:var(--slate);margin-left:4px;font-family:IBM Plex Sans,sans-serif;font-size:1rem;font-weight:500}.class-subjects{color:var(--slate);margin-top:12px;font-size:.86rem}.class-foot{justify-content:space-between;align-items:center;margin-top:auto;padding-top:18px;display:flex}.status{border-radius:20px;padding:3px 10px;font-size:.74rem;font-weight:700}.status.live{color:var(--leaf);background:#e7f0ea}.status.soon{background:var(--paper-dim);color:var(--slate)}.class-link{color:var(--ink);border-bottom:1px solid var(--ink);padding-bottom:1px;font-size:.85rem;font-weight:600}.class-card.disabled .class-link{color:var(--slate);border-color:var(--line);cursor:default}.class-card.featured{background:var(--ink);border-color:var(--ink)}.class-card.featured .class-num,.class-card.featured .class-num span,.class-card.featured .class-subjects{color:var(--paper)}.class-card.featured .class-subjects{color:#c8cfe0}.class-card.featured .class-link{color:var(--marigold);border-color:var(--marigold)}.trust{border-top:1px solid var(--line);border-bottom:1px solid var(--line);padding:22px 0}.trust-inner{color:var(--slate);text-align:center;flex-wrap:wrap;justify-content:center;gap:40px;font-size:.88rem;display:flex}.trust-inner strong{color:var(--ink);font-family:Lora,serif;font-weight:600}footer{background:var(--ink);color:#96a0b8;padding:36px 0;font-size:.85rem}.footer-inner{flex-wrap:wrap;justify-content:space-between;gap:14px;display:flex}.footer-links{border-top:1px solid #ffffff1f;flex-wrap:wrap;gap:24px;margin-top:20px;padding-top:20px;font-size:.82rem;display:flex}.footer-links a{color:#96a0b8}.footer-links a:hover,.footer-inner .logo{color:var(--paper)}.section-divider{letter-spacing:.02em;color:var(--paper);background:var(--ink);border-radius:5px;margin:34px 0 14px;padding:9px 16px;font-family:IBM Plex Mono,monospace;font-size:.76rem}.section-divider:first-child{margin-top:6px}.qa-card{border:1px solid var(--line);background:var(--paper);border-radius:8px;margin-bottom:14px;padding:22px 24px}.q-label{color:var(--brick);margin-bottom:6px;font-family:IBM Plex Mono,monospace;font-size:.74rem}.q-text{font-family:Lora,serif;font-size:1.05rem;font-weight:600;line-height:1.4}.table-scroll{-webkit-overflow-scrolling:touch;margin:14px 0 0;overflow-x:auto}.q-table{border-collapse:collapse;min-width:100%;font-size:.86rem}.q-table th,.q-table td{border:1px solid var(--line);text-align:center;white-space:nowrap;padding:6px 12px}.q-table thead th{background:var(--paper-dim);color:var(--ink);font-weight:600}.q-table td{color:var(--ink-soft)}.q-table-given th[scope=row]{background:var(--paper-dim);color:var(--ink);text-align:left;white-space:normal;min-width:130px;font-weight:600}.q-table-given tr:first-child td{color:var(--ink);font-weight:600}.ledger{margin-top:14px}.ledger-title{color:var(--ink);margin-bottom:8px;font-family:Lora,serif;font-size:.95rem;font-weight:600}.ledger-table{border-collapse:collapse;min-width:100%;margin-bottom:14px;font-size:.84rem}.ledger-table caption{caption-side:top;text-align:left;color:var(--ink-soft);padding-bottom:6px;font-size:.8rem;font-weight:600}.ledger-table th,.ledger-table td{border:1px solid var(--line);white-space:nowrap;padding:6px 10px}.ledger-table thead th{background:var(--ink);color:var(--paper);text-align:center;font-weight:600}.ledger-table td{color:var(--ink-soft);text-align:left}.ledger-amount{font-family:IBM Plex Mono,monospace;font-size:.82rem;text-align:right!important}.ledger-total td{color:var(--ink);border-top:2px solid var(--ink);background:var(--paper-dim);font-weight:700}.math-line{margin-top:4px;line-height:1.9;display:block}.math-line:first-child{margin-top:0}.math-arrow{color:var(--marigold-deep);margin-right:2px;font-weight:700}.math-aside{color:var(--slate);font-size:.82em}.math-fallback{font-family:inherit}.q-text .math-line{display:inline}.q-diagram{border:1px solid var(--line);background:#fff;border-radius:6px;max-width:100%;height:auto;margin:14px 0 0;padding:8px;display:block}.body-text{color:var(--ink-soft);white-space:pre-line;font-size:.96rem}.trick-box{background:var(--paper-dim);color:var(--ink-soft);border-radius:5px;margin-top:16px;padding:12px 14px;font-size:.88rem}.trick-box .lbl{color:var(--marigold-deep);font-family:IBM Plex Mono,monospace;font-size:.72rem;font-weight:700}.trick-box p{margin:6px 0 0}.ad-slot{text-align:center;margin:34px 0}.ad-label{letter-spacing:.05em;color:var(--slate);text-transform:uppercase;margin-bottom:6px;font-size:.68rem;display:block}.ad-box{border:1px dashed var(--line);color:var(--slate);background:var(--paper-dim);border-radius:6px;padding:26px 16px;font-size:.85rem}.subject-grid{grid-template-columns:repeat(4,1fr);gap:18px;display:grid}.subject-grid>a{height:100%;display:block}@media (max-width:900px){.subject-grid{grid-template-columns:repeat(2,1fr)}}@media (max-width:520px){.subject-grid{grid-template-columns:1fr}}.subject-card{border:1px solid var(--line);background:var(--paper);border-radius:6px;flex-direction:column;height:100%;padding:22px 20px;transition:border-color .15s;display:flex;position:relative}.subject-card:hover{border-color:var(--ink)}.subject-swatch{border-radius:3px;width:34px;height:6px;margin-bottom:16px}.subject-card h3{font-size:1.08rem;font-weight:600}.subject-card .detail{color:var(--slate);margin-top:10px;margin-bottom:14px;font-size:.86rem}.subject-card .status{align-self:flex-start;margin-top:auto}.back-link{color:var(--slate);font-size:.85rem}.back-link:hover{color:var(--ink)}.chapter-head{padding:30px 0 6px}.chapter-head .eyebrow{color:var(--marigold-deep);font-family:IBM Plex Mono,monospace;font-size:.78rem}.chapter-head h1{margin-top:8px;font-size:1.55rem;line-height:1.3}.chapter-head .count{color:var(--slate);margin-top:8px;font-size:.85rem}.theme{--g1:#5b3df5;--g2:#c13df5}.theme[data-cls="6"]{--g1:#e8553a;--g2:#f08a1f}.theme[data-cls="7"]{--g1:#00997a;--g2:#0969c9}.theme[data-cls="8"]{--g1:#0969c9;--g2:#6c5ce7}.theme[data-cls="9"]{--g1:#d6336c;--g2:#e8553a}.theme[data-cls="10"]{--g1:#5b3df5;--g2:#c13df5}.theme[data-cls="11"]{--g1:#0f9d8a;--g2:#2d5bff}.theme[data-cls="12"]{--g1:#d97706;--g2:#d6336c}body{background:#f8f7fc}nav:not(.breadcrumb){background:linear-gradient(135deg,var(--g1),var(--g2));border-bottom:0}nav:not(.breadcrumb) .logo,nav:not(.breadcrumb) .nav-links,nav:not(.breadcrumb) .nav-links a:hover{color:#fff}nav:not(.breadcrumb) .nav-links{opacity:.9}.logo-icon{box-sizing:border-box;background:#fff;border-radius:8px;width:30px;height:30px;padding:3px}.nav-cta{border-radius:999px;color:#1b1330!important;background:#fff!important}.nav-cta:hover{filter:none;transform:translateY(-1px)}nav.breadcrumb{background:0 0;border:0;position:static}.hero{background:linear-gradient(135deg,var(--g1),var(--g2))}.hero-eyebrow{color:#ffe9b8}.hero p.lede{color:#ffffffe0}.breadcrumb-bar{background:#f0eefa;border-bottom:1px solid #e4e0f3}.breadcrumb-current{background:linear-gradient(135deg,var(--g1),var(--g2));color:#fff}.sticky-header{background:#f8f7fc}.section-divider{background:linear-gradient(135deg,var(--g1),var(--g2));color:#fff;border-radius:12px}.qa-card{background:#fff;border-color:#e7e3f4;border-radius:18px;box-shadow:0 6px 18px #1b13300f}.q-label{color:var(--g1)}.ledger-table thead th{background:linear-gradient(135deg,var(--g1),var(--g2))}.trick-box{background:#f2f0fb;border-radius:12px}.trick-box .lbl,.chapter-head .eyebrow{color:var(--g1)}.subject-card{background:#fff;border-color:#e7e3f4;border-radius:20px;padding:24px 22px;transition:transform .18s,box-shadow .18s,border-color .18s;box-shadow:0 6px 18px #1b13300f}a:hover>.subject-card{border-color:var(--g1);transform:translateY(-4px);box-shadow:0 16px 30px #1b133024}.subject-swatch{width:48px;height:8px;background:linear-gradient(90deg,var(--g1),var(--g2))!important}.status.live{background:linear-gradient(135deg,var(--g1),var(--g2));color:#fff}.status.soon{color:#5b5675;background:#eeebf8}.pricing{text-align:center;background:linear-gradient(#eeebf8,#f8f7fc)}footer{background:linear-gradient(135deg,#14102b,#1b2a4a)}.spot{color:#fff;background:linear-gradient(135deg,var(--g1),var(--g2));transition:background .3s}.spot nav{background:0 0;position:relative}.spot-inner{text-align:center;flex-direction:column;align-items:center;gap:clamp(16px,3.5vw,26px);max-width:900px;margin:0 auto;padding:14px 16px 56px;display:flex}.spot-title{color:#fff;max-width:640px;font-size:clamp(1.5rem,4.5vw,2.3rem);line-height:1.2}.spot-tabs{flex-wrap:wrap;justify-content:center;gap:6px;display:flex}.spot-tab{font:inherit;cursor:pointer;color:#fff;background:#ffffff1f;border:1px solid #fff6;border-radius:999px;min-height:44px;padding:10px 18px;font-size:.92rem;font-weight:600}.spot-tab.on{color:#1b1330;background:#fff}.spot-note{background:#ffffff29;border-radius:999px;padding:6px 14px;font-size:.82rem}.spot-kicker{letter-spacing:.1em;opacity:.9;overflow-wrap:anywhere;font-size:.8rem;font-weight:600}.spot-row{justify-content:center;align-items:center;gap:clamp(8px,3vw,24px);width:100%;display:flex}.spot-num{text-align:center;min-width:0;font-family:Lora,serif;font-size:clamp(110px,34vw,200px);font-weight:700;line-height:.9}.spot-num.two{font-size:clamp(84px,26vw,154px);line-height:1.17}.spot-arrow{color:#fff;cursor:pointer;background:#ffffff24;border:1px solid #fff6;border-radius:50%;flex:none;width:48px;height:48px;font-size:22px}.spot-arrow:hover{background:#ffffff47}.spot-dots{align-items:center;gap:8px;display:flex}.spot-dot{cursor:pointer;background:#fff6;border:0;border-radius:999px;width:12px;height:12px;padding:0;transition:width .2s}.spot-dot.on{background:#fff;width:36px}.spot-chips{flex-wrap:wrap;justify-content:center;gap:10px;max-width:720px;display:flex}.spot-chip{font:inherit;cursor:pointer;color:#fff;background:#ffffff1f;border:1px solid #ffffff80;border-radius:999px;min-height:44px;padding:10px 22px;font-weight:600}.spot-chip.on{color:#1b1330;background:#fff}.spot-subject{box-sizing:border-box;background:#ffffff2e;border:1px solid #ffffff59;border-radius:14px;align-items:center;gap:6px;min-height:44px;padding:10px 18px;font-weight:600;transition:transform .15s,background .15s;display:inline-flex}.spot-subject.off{opacity:.65;border-style:dashed}.spot-subject small{font-size:.68rem;font-weight:700}.spot-cta{color:#1b1330;background:#fff;border-radius:999px;align-items:center;min-height:44px;padding:12px 28px;font-weight:700;display:inline-flex;box-shadow:0 10px 24px #0003}.spot-soon{background:#ffffff2e;border:1px dashed #fff9;border-radius:999px;padding:12px 24px;font-weight:600}.spot-foot{opacity:.9;max-width:320px;font-size:.88rem}@media (max-width:560px){.spot .nav-cta{padding:8px 14px}}.spot-seg{background:#0a081e47;border:1px solid #ffffff40;border-radius:999px;gap:2px;padding:5px;display:inline-flex}.spot-seg .spot-chip{background:0 0;border:0;padding:10px 22px}.spot-seg .spot-chip.on{color:#1b1330;background:#fff;box-shadow:0 4px 12px #00000040}.spot-subject{color:#1b1330;background:#fffffff2;border:0;border-radius:8px;padding:12px 18px;box-shadow:0 6px 16px #0000002e}a.spot-subject:hover{background:#fff;transform:translateY(-3px)}.spot-subject span{color:var(--g1);font-weight:800}.spot-subject.off{color:#fff;box-shadow:none;opacity:1;background:#ffffff24;border:1px dashed #ffffff8c}.share-float{z-index:60;position:fixed;top:76px;right:14px}.share-toggle{cursor:pointer;background:linear-gradient(135deg,var(--g1),var(--g2));border:2px solid #fff;border-radius:50%;justify-content:center;align-items:center;width:46px;height:46px;padding:0;transition:transform .15s;display:flex;box-shadow:0 8px 20px #00000047}.share-toggle:hover{transform:scale(1.08)}.share-menu{width:210px;color:var(--ink);background:#fff;border-radius:14px;padding:8px;position:absolute;top:56px;right:0;box-shadow:0 18px 40px #00000047}.share-item{box-sizing:border-box;cursor:pointer;width:100%;min-height:44px;font:inherit;color:var(--ink);text-align:left;background:0 0;border:0;border-radius:10px;align-items:center;gap:12px;padding:6px 8px;font-size:.92rem;font-weight:600;display:flex}.share-item:hover{background:#f2f0fb}.share-ico{border-radius:50%;flex:none;justify-content:center;align-items:center;width:32px;height:32px;display:inline-flex}.share-ico svg{width:18px;height:18px}@media (max-width:600px){.share-float{top:70px;right:8px}.share-toggle{opacity:.9;border-width:1.5px;width:34px;height:34px;box-shadow:0 4px 12px #00000040}.share-toggle svg{width:16px;height:16px}.share-menu{width:190px;top:42px}}.share-menu{grid-template-columns:repeat(3,44px);gap:10px;width:auto;padding:12px;display:grid}.share-item{color:#fff;border-radius:50%;justify-content:center;width:44px;height:44px;min-height:0;padding:0}.share-item:hover{background-blend-mode:normal;transform:translateY(-3px);box-shadow:0 8px 16px #00000040}.share-item svg{width:20px;height:20px}.share-copied{text-align:center;color:var(--g1);grid-column:1/-1;font-size:.8rem;font-weight:600}@media (max-width:600px){.share-menu{grid-template-columns:repeat(3,40px);gap:8px;padding:10px}.share-item{width:40px;height:40px}}.share-menu{flex-direction:column;align-items:center;gap:10px;width:auto;padding:10px;display:flex}@media (max-width:600px){.share-menu{grid-template-columns:none;gap:8px;padding:8px}}.share-copied{max-width:120px}.unlock-banner{color:#fff;background:linear-gradient(135deg,var(--g1),var(--g2));border-radius:18px;flex-wrap:wrap;justify-content:space-between;align-items:center;gap:10px 14px;margin:0 0 14px;padding:16px 20px;scroll-margin-top:140px;display:flex;box-shadow:0 10px 22px #0000002e}.unlock-banner.flash,.unlock-banner:target{animation:1.4s unlock-pulse}@keyframes unlock-pulse{0%,to{transform:scale(1);box-shadow:0 10px 22px #0000002e}30%{transform:scale(1.03);box-shadow:0 0 0 4px #ffd08a,0 16px 32px #0000004d}}.unlock-text{flex:240px;font-family:Lora,serif;font-size:1.1rem;font-weight:700;line-height:1.3}.unlock-actions{flex-wrap:wrap;align-items:center;gap:14px;display:flex}.unlock-buy{color:#1b1330;background:#fff;border-radius:999px;align-items:center;min-height:44px;padding:10px 22px;font-size:.92rem;font-weight:700;display:inline-flex}.unlock-paid{color:#fff;font-size:.85rem;text-decoration:underline}