:root{--ink:#20283d;--muted:#58647a;--paper:#faf8f3;--card:#fff;--line:#e4e7eb;--navy:#20365f;--blue:#dcecfb;--mint:#daf1e6;--peach:#ffead9;--lav:#eee8fb;--yellow:#fff2c6;--accent:#ff725e;--shadow:0 12px 34px rgba(31,48,79,.08)}
    *{box-sizing:border-box}
    html{scroll-behavior:smooth}
    body{margin:0;background:var(--paper);color:var(--ink);font-family:ui-sans-serif,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;line-height:1.58}
    a{color:#2458a6}
    button,input{font:inherit}
    button{cursor:pointer}
    .skip{position:absolute;left:-9999px;top:8px;background:white;padding:.6rem 1rem;z-index:10}.skip:focus{left:8px}
    .topbar{background:#fff;border-bottom:1px solid var(--line)}
    .topbar-inner,.wrap{max-width:1160px;margin:auto;padding-left:24px;padding-right:24px}
    .topbar-inner{min-height:68px;display:flex;align-items:center;justify-content:space-between;gap:20px}
    .brand{font-size:.93rem;font-weight:900;letter-spacing:.06em;text-transform:uppercase;color:var(--navy)}
    .toplinks{display:flex;align-items:center;gap:22px;font-size:.9rem;font-weight:700}
    .toplinks a{text-decoration:none;color:var(--navy)}.toplinks a:hover{text-decoration:underline}
    .hero{padding:68px 0 46px;background:radial-gradient(circle at 82% 18%,#fee1cf 0 13%,transparent 13.2%),radial-gradient(circle at 92% 82%,#dcecfb 0 8%,transparent 8.2%),linear-gradient(145deg,#fff9ed,#f4f8ff)}
    .hero-grid{display:grid;grid-template-columns:minmax(0,1.25fr) minmax(260px,.75fr);gap:34px;align-items:center}
    .eyebrow{display:inline-block;text-transform:uppercase;letter-spacing:.13em;font-size:.76rem;font-weight:900;color:#9a4435;background:#ffe8dc;padding:6px 11px;border-radius:100px}
    h1,h2,h3,p{margin-top:0}
    h1{font-size:clamp(2.5rem,5vw,4.6rem);line-height:1.08;letter-spacing:-.055em;color:var(--navy);max-width:720px;margin:18px 0 18px}
    .lead{font-size:1.15rem;max-width:640px;color:#42506a;margin-bottom:24px}
    .hero-actions{display:flex;flex-wrap:wrap;gap:12px;align-items:center}
    .button{display:inline-flex;align-items:center;justify-content:center;gap:8px;background:var(--navy);color:white;border-radius:12px;padding:12px 17px;text-decoration:none;font-weight:800;border:2px solid var(--navy)}
    .button:hover{background:#304e83}.button.secondary{background:white;color:var(--navy)}.button.secondary:hover{background:#f4f7fb}
    .hero-art{min-height:275px;background:white;border:2px solid var(--navy);border-radius:22px;box-shadow:12px 12px 0 #bcd5ef;padding:24px;transform:rotate(2deg);position:relative}
    .hero-art small{display:block;color:#6d7b92;text-transform:uppercase;font-weight:900;letter-spacing:.12em;margin-bottom:20px}
    .art-line{display:flex;align-items:center;justify-content:space-between;border-bottom:1px dashed #cbd4e0;padding:10px 0;font-weight:850;color:var(--navy)}
    .art-line span:last-child{background:var(--yellow);border-radius:9px;padding:4px 9px}
    .art-note{font-size:.85rem;color:var(--muted);padding-top:18px;margin:0}
    .intro{padding:34px 0 18px}
    .intro-grid{display:grid;grid-template-columns:1.1fr .9fr;gap:18px}
    .intro-card{background:white;border:1px solid var(--line);border-radius:18px;padding:22px;box-shadow:var(--shadow)}
    .intro-card h2{font-size:1.2rem;margin-bottom:9px;color:var(--navy)}
    .intro-card p{margin-bottom:0;color:var(--muted)}
    .progress-track{height:12px;background:#e5eaf1;border-radius:100px;overflow:hidden;margin:13px 0 7px}.progress-fill{width:0;height:100%;background:linear-gradient(90deg,#50b99d,#6e94da);border-radius:100px;transition:width .3s}
    .progress-text{font-size:.9rem;font-weight:700;color:var(--muted)}
    .contents{padding:24px 0 16px}.section-kicker{text-transform:uppercase;letter-spacing:.12em;font-weight:900;color:#7a5777;font-size:.78rem;margin-bottom:8px}
    .contents h2{font-size:1.65rem;letter-spacing:-.03em;color:var(--navy);margin-bottom:14px}
    .topic-links{display:flex;flex-wrap:wrap;gap:9px}
    .topic-links a{font-weight:800;font-size:.89rem;border-radius:100px;padding:8px 13px;background:white;border:1px solid #d8dfe8;color:var(--navy);text-decoration:none}
    .topic-links a:hover,.topic-links a:focus{background:var(--blue);border-color:#a9c8e6}
    .lessons{padding:16px 0 70px}
    .lesson{scroll-margin-top:20px;margin:22px 0;background:var(--card);border:1px solid var(--line);border-radius:24px;overflow:hidden;box-shadow:var(--shadow)}
    .lesson-head{padding:26px 30px 24px;background:var(--tint);border-bottom:1px solid var(--line);display:grid;grid-template-columns:1fr auto;gap:20px;align-items:start}
    .lesson-number{display:inline-block;background:white;color:var(--navy);font-weight:900;font-size:.78rem;letter-spacing:.08em;text-transform:uppercase;border-radius:100px;padding:5px 10px;margin-bottom:10px}
    .lesson h2{font-size:clamp(1.6rem,3vw,2.15rem);letter-spacing:-.035em;line-height:1.15;margin-bottom:8px;color:var(--navy)}
    .lesson-head p{margin:0;max-width:700px;color:#46536b}
    .source-tag{font-size:.79rem;font-weight:800;color:#53617b;white-space:nowrap;background:rgba(255,255,255,.72);border-radius:8px;padding:7px 9px}
    .lesson-body{padding:28px 30px 30px;display:grid;grid-template-columns:minmax(0,1fr) minmax(0,.92fr);gap:24px 34px}
    .lesson-body>div{min-width:0}.full{grid-column:1/-1}
    .mini-title{font-size:.8rem;letter-spacing:.1em;text-transform:uppercase;font-weight:900;color:#796181;margin-bottom:8px}
    .plain{font-size:1rem;margin-bottom:0}.steps{margin:0;padding-left:22px}.steps li{padding-left:4px;margin:7px 0}.steps li::marker{font-weight:900;color:#dc6b56}
    .example{background:#f4f7fb;border:1px solid #dce5f0;border-radius:15px;padding:17px 19px}.example .mini-title{color:#35638d}.example p:last-child{margin-bottom:0}
    .math{font-family:ui-serif,Georgia,serif;font-size:1.12em;font-weight:700;color:#20365f;white-space:normal}
    .math-line{display:block;margin:7px 0;color:#20365f;font-weight:750}
    .prep{background:#fff9e7;border:1px solid #f4e6b4;border-radius:15px;padding:17px 19px}
    .prep .mini-title{color:#8a6823}.prep p{margin:0}
    .watch{border-left:4px solid #ef9274;padding:8px 13px;background:#fff7f3;border-radius:0 10px 10px 0;font-size:.93rem;color:#5c5360}
    .practice{border-top:1px solid var(--line);padding:19px 30px 24px;background:#fcfdfd;display:grid;grid-template-columns:1fr auto;gap:14px;align-items:start}
    .practice strong{color:var(--navy)}.practice p{margin:4px 0 0}
    details{grid-column:1/-1}.answer-toggle{background:var(--navy);color:white;padding:8px 13px;border-radius:10px;font-weight:800;list-style:none;display:inline-block;font-size:.9rem;cursor:pointer}
    .answer-toggle::-webkit-details-marker{display:none}details[open] .answer-toggle{background:#385c8b}.answer{margin-top:12px;background:#eaf7f0;border:1px solid #bce0c7;padding:13px 16px;border-radius:11px}
    .extra-practice{border-top:1px solid var(--line);padding:26px 30px 30px;background:#fff}.extra-practice h3{font-size:1.18rem;color:var(--navy);margin:0 0 5px}.extra-practice>p{color:var(--muted);margin:0 0 17px;font-size:.92rem}.quiz-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}.quiz-card{border:1px solid #dce2eb;background:#fbfcfe;border-radius:14px;padding:16px;display:flex;flex-direction:column;gap:11px;min-width:0}.quiz-level{align-self:flex-start;border-radius:100px;padding:3px 9px;font-size:.72rem;letter-spacing:.07em;text-transform:uppercase;font-weight:900;color:#365b79;background:#e6f1fb}.quiz-card:nth-child(2) .quiz-level{color:#59623a;background:#ecf1d7}.quiz-card:nth-child(3) .quiz-level{color:#8a4f48;background:#ffebe3}.quiz-question{font-weight:800;color:var(--ink);margin:0;flex:1}.quiz-card details{margin-top:auto}.quiz-card summary{font-size:.82rem}.quiz-card .answer{font-size:.9rem;line-height:1.5;margin-top:10px}.quiz-card .answer p{margin:0}
    .done-label{display:flex;align-items:center;gap:8px;font-size:.86rem;font-weight:800;color:#405272;white-space:nowrap}.done-label input{width:19px;height:19px;accent-color:#28896e}
    .lesson.is-done{border-color:#add9c5}.lesson.is-done .lesson-number::after{content:' ✓';color:#268267}
    .study-plan{background:#20365f;color:white;border-radius:24px;padding:30px;margin-top:35px;display:grid;grid-template-columns:.7fr 1.3fr;gap:24px}
    .study-plan h2{font-size:1.7rem;margin:0}.study-plan p{color:#dfe8f6}.study-plan ol{margin:0;padding-left:22px;display:grid;gap:8px}
    .study-plan li{padding-left:5px}.study-plan li::marker{color:#ffbf91;font-weight:900}
    .footer{border-top:1px solid var(--line);padding:24px 0 36px;color:var(--muted);font-size:.88rem}.footer-inner{display:flex;justify-content:space-between;gap:14px;flex-wrap:wrap}
    @media(max-width:800px){.hero-grid,.intro-grid,.lesson-body,.study-plan{grid-template-columns:1fr}.hero-art{max-width:440px;min-height:235px}.hero{padding-top:46px}.lesson-head{grid-template-columns:1fr}.source-tag{justify-self:start}.full{grid-column:1}.practice{grid-template-columns:1fr}.done-label{white-space:normal}.quiz-grid{grid-template-columns:1fr}}
    @media(max-width:540px){.topbar-inner,.wrap{padding-left:17px;padding-right:17px}.topbar-inner{min-height:60px}.toplinks{gap:12px;font-size:.8rem}.toplinks a:last-child{display:none}.hero{padding:34px 0}.hero-art{display:none}.lesson-head,.lesson-body,.practice,.extra-practice{padding-left:19px;padding-right:19px}.lesson-body{gap:21px}.lesson{border-radius:18px}.study-plan{padding:22px}}
    @media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}.progress-fill{transition:none}}
    @media print{body{background:white}.topbar,.hero-actions,.topic-links,.done-label,.answer-toggle{display:none!important}.hero{padding:18px 0;background:white}.hero-art{display:none}.intro{padding:0}.lesson,.intro-card{break-inside:avoid;box-shadow:none}.lesson{margin:14px 0}.lesson-body{gap:13px}.practice{padding-top:10px}details .answer{display:block}.study-plan{background:#eee;color:#111}.study-plan p{color:#111}}
/* Multi-page navigation */
a.brand{text-decoration:none}
.home-page .hero{padding:60px 0 52px}
.home-page .hero-art{min-height:245px}
.home-intro{padding:37px 0 13px}
.home-intro h2{color:var(--navy);font-size:1.8rem;letter-spacing:-.03em;margin-bottom:5px}
.home-intro p{color:var(--muted);margin-bottom:0}
.home-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px;padding:17px 0 26px}
.home-card{display:flex;flex-direction:column;min-height:215px;background:#fff;border:1px solid var(--line);border-radius:19px;padding:22px 23px;text-decoration:none;color:var(--ink);box-shadow:var(--shadow);transition:transform .15s,box-shadow .15s}
.home-card:hover,.home-card:focus-visible{transform:translateY(-3px);box-shadow:0 16px 32px rgba(31,48,79,.12);border-color:#b8cbe3}
.home-card .card-top{display:flex;justify-content:space-between;gap:12px;color:#5b6880;font-size:.75rem;font-weight:900;text-transform:uppercase;letter-spacing:.07em}
.home-card h3{font-size:1.32rem;color:var(--navy);letter-spacing:-.025em;line-height:1.2;margin:16px 0 8px}
.home-card p{color:#55627a;margin:0 0 18px;max-width:50ch}
.home-card .card-cta{font-weight:900;color:#2458a6;margin-top:auto}
.home-plan{padding-bottom:62px}
.topic-shell{padding-top:34px;padding-bottom:60px}
.topic-toolbar{display:flex;align-items:center;justify-content:space-between;gap:14px;margin-bottom:17px;color:#607089;font-size:.86rem;font-weight:800}
.topic-toolbar a{color:var(--navy);text-decoration:none}.topic-toolbar a:hover{text-decoration:underline}
.topic-toolbar .watch-link{background:#fff0e4;border:1px solid #f3d0b7;border-radius:100px;color:#8e4a34;padding:6px 12px;text-decoration:none}.topic-toolbar .watch-link:hover{background:#ffe3d1;text-decoration:none}
.topic-page .lesson{margin:0}
.lesson h1{font-size:clamp(1.6rem,3vw,2.15rem);letter-spacing:-.035em;line-height:1.15;margin-bottom:8px;color:var(--navy)}
.page-nav{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:13px;margin-top:22px}
.page-nav a{display:block;background:white;border:1px solid var(--line);border-radius:15px;padding:16px 18px;text-decoration:none;color:var(--navy);font-weight:900}
.page-nav a:hover,.page-nav a:focus-visible{background:var(--blue)}
.page-nav small{display:block;color:#718098;text-transform:uppercase;letter-spacing:.08em;margin-bottom:4px}
.page-nav .next{text-align:right;grid-column:2}
.topic-footnote{color:var(--muted);font-size:.88rem;margin-top:26px}
@media(max-width:800px){.home-grid{grid-template-columns:1fr}}
@media(max-width:540px){.home-page .hero{padding:36px 0}.home-card{min-height:0;padding:19px}.topic-shell{padding-top:20px}.topic-toolbar{align-items:flex-start;flex-direction:column}.page-nav{grid-template-columns:1fr}.page-nav .next{grid-column:1}.page-nav a{text-align:left!important}}
@media(max-width:540px){.brand{white-space:nowrap;font-size:.78rem}.toplinks a:nth-child(2){display:none}}
@media print{.home-card,.page-nav a{box-shadow:none}.topic-toolbar,.page-nav{display:none}}