:root{--bg:#eef2f8;--card:#fff;--ink:#111827;--muted:#64748b;--brand:#1c4ed8;--brand2:#f97316;--ok:#0f9f6e;--bad:#c2410c;--line:#dbe3ef;--soft:#f8fafc;--shadow:0 22px 60px rgba(15,23,42,.12)}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;font-family:Inter,system-ui,-apple-system,Segoe UI,Roboto,Arial,sans-serif;background:radial-gradient(circle at 10% 0,#dbeafe,transparent 30%),var(--bg);color:var(--ink);line-height:1.62}.topbar{position:sticky;top:0;z-index:20;background:rgba(255,255,255,.88);backdrop-filter:blur(18px);border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;padding:14px clamp(16px,4vw,54px)}.brand{display:flex;gap:14px;align-items:center}.brand h1{font-size:1.06rem;margin:0}.brand p{margin:0;color:var(--muted);font-size:.86rem}.badge{background:linear-gradient(135deg,var(--brand),#0ea5e9);color:#fff;border-radius:16px;padding:11px 13px;font-weight:900;box-shadow:0 10px 24px rgba(28,78,216,.25)}nav{display:flex;gap:12px}nav a{color:var(--ink);text-decoration:none;font-weight:800;font-size:.92rem}.hero{display:grid;grid-template-columns:minmax(0,1fr) 330px;gap:28px;padding:70px clamp(16px,5vw,70px);background:radial-gradient(circle at top right,#bfdbfe,transparent 36%),linear-gradient(135deg,#fff,#eef4ff)}.eyebrow{text-transform:uppercase;letter-spacing:.13em;color:var(--brand);font-weight:900;font-size:.8rem}.hero h2{font-size:clamp(2rem,4.5vw,4.7rem);line-height:1.02;margin:10px 0 18px}.hero p{max-width:900px;color:#334155;font-size:1.13rem}.actions{display:flex;gap:12px;margin-top:26px;flex-wrap:wrap}.btn,button{border:1px solid var(--line);background:#fff;color:var(--ink);border-radius:14px;padding:11px 16px;text-decoration:none;font-weight:900;cursor:pointer;box-shadow:0 3px 0 rgba(15,23,42,.04)}.primary,.btn.primary{background:linear-gradient(135deg,var(--brand),#2563eb);border-color:var(--brand);color:#fff}.stats{display:grid;gap:14px;align-content:center}.stats div{background:#fff;border:1px solid var(--line);border-radius:24px;padding:26px;box-shadow:var(--shadow)}.stats strong{display:block;font-size:2.4rem;color:var(--brand);line-height:1}.stats span{color:var(--muted);font-weight:800}main{padding:28px clamp(12px,3vw,46px)}.panel{background:rgba(255,255,255,.85);border:1px solid var(--line);border-radius:30px;padding:clamp(16px,3vw,32px);box-shadow:var(--shadow);margin-bottom:30px}.section-head{display:flex;justify-content:space-between;gap:20px;align-items:end;border-bottom:1px solid var(--line);padding-bottom:18px;margin-bottom:20px}.section-head h2{margin:0;font-size:1.8rem}.section-head p{margin:0;color:var(--muted);max-width:800px}.tools,.quiz-toolbar{display:flex;gap:10px;flex-wrap:wrap;align-items:center;margin-bottom:22px}.tools input{flex:1;min-width:280px;border:1px solid var(--line);border-radius:16px;padding:14px 15px;font-size:1rem;background:#fff}.tools select{border:1px solid var(--line);border-radius:16px;padding:14px;background:#fff}.chapter-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(235px,1fr));gap:13px;margin-bottom:24px}.chapter-card{border:1px solid var(--line);border-top:5px solid var(--chap);border-radius:20px;padding:15px;background:linear-gradient(180deg,#fff,#f8fafc);cursor:pointer;transition:.18s transform,.18s box-shadow}.chapter-card:hover{transform:translateY(-2px);box-shadow:0 12px 32px rgba(15,23,42,.1)}.chapter-emoji{font-size:1.55rem}.chapter-card h3{margin:4px 0 5px;font-size:1rem}.chapter-card span{color:var(--muted);font-size:.9rem}.page-list{display:grid;gap:24px}.page-card{border:1px solid var(--line);border-radius:28px;overflow:hidden;background:#fff;box-shadow:0 14px 40px rgba(15,23,42,.08)}.page-head{display:flex;justify-content:space-between;gap:16px;padding:18px 20px;border-bottom:1px solid var(--line);background:linear-gradient(90deg,#fff,#f8fafc)}.page-title{display:flex;gap:12px;align-items:center}.chapter-dot{display:grid;place-items:center;width:42px;height:42px;border-radius:14px;background:color-mix(in srgb,var(--chap) 12%,white);border:1px solid color-mix(in srgb,var(--chap) 30%,white);font-size:1.3rem}.page-head h3{margin:0;font-size:1.12rem}.page-head small{color:var(--muted);font-weight:800}.page-body.pro{display:grid;grid-template-columns:minmax(380px,500px) minmax(0,1fr);gap:24px;padding:22px;background:linear-gradient(180deg,#fff,#f8fafc)}.original-pane{min-width:0}.sticky-original{position:sticky;top:92px}.page-img{width:100%;border-radius:18px;border:1px solid var(--line);box-shadow:0 14px 34px rgba(0,0,0,.14);background:#fff}.quick{display:flex;gap:8px;flex-wrap:wrap;margin-top:12px}.pill{font-size:.79rem;padding:6px 10px;border-radius:999px;background:#eaf1ff;color:#1d4ed8;font-weight:900}.linkpill{text-decoration:none}.study-pane{display:grid;gap:16px;align-content:start}.study-hero-card{border:1px solid color-mix(in srgb,var(--chap) 20%,white);background:linear-gradient(135deg,color-mix(in srgb,var(--chap) 10%,white),#fff);border-radius:22px;padding:16px 18px}.study-hero-card span{display:block;color:var(--chap);font-size:.8rem;font-weight:1000;text-transform:uppercase;letter-spacing:.12em}.study-hero-card strong{display:block;font-size:1.15rem}.mini-title{font-weight:1000;color:#0f172a;letter-spacing:.01em;margin-bottom:10px}.visual-cards,.key-facts,.readable,.raw{background:#fff;border:1px solid var(--line);border-radius:22px;padding:17px;box-shadow:0 8px 24px rgba(15,23,42,.04)}.definition-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(210px,1fr));gap:10px}.definition-grid article{border:1px solid #e2e8f0;background:linear-gradient(180deg,#fff,#f8fafc);border-radius:16px;padding:12px}.definition-grid b{display:block;color:var(--chap);font-size:.98rem;margin-bottom:5px}.definition-grid span{display:block;color:#334155;font-size:.92rem}.key-facts{display:grid;gap:8px}.fact{border-left:5px solid var(--chap);background:#f8fafc;border-radius:12px;padding:10px 12px;color:#263244}.readable h4{margin:18px 0 8px;font-size:1.18rem;color:var(--chap);border-bottom:1px solid #e2e8f0;padding-bottom:6px}.readable h4:first-of-type{margin-top:0}.readable p{margin:0 0 11px;color:#1f2937;font-size:1.02rem}.nice-list,.number-list{margin:0 0 13px 0;padding:0;display:grid;gap:8px}.nice-list li,.number-list li{list-style:none;position:relative;background:#f8fafc;border:1px solid #e2e8f0;border-radius:14px;padding:10px 12px 10px 38px}.nice-list li:before{content:'◆';position:absolute;left:14px;color:var(--chap);font-size:.82rem}.number-list{counter-reset:item}.number-list li{counter-increment:item}.number-list li:before{content:counter(item);position:absolute;left:11px;top:10px;width:20px;height:20px;border-radius:50%;display:grid;place-items:center;background:var(--chap);color:white;font-size:.72rem;font-weight:900}.raw summary{font-weight:900;color:#475569;cursor:pointer}.raw pre{white-space:pre-wrap;background:#0f172a;color:#e2e8f0;border-radius:14px;padding:14px;overflow:auto;max-height:420px}.hidden{display:none}.original-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(180px,1fr));gap:14px}.thumb{display:block;text-decoration:none;color:var(--ink);border:1px solid var(--line);border-radius:16px;overflow:hidden;background:#fff;box-shadow:0 6px 18px rgba(15,23,42,.06)}.thumb img{width:100%;display:block}.thumb span{display:block;padding:9px 11px;font-weight:900;font-size:.86rem}.question{border:1px solid var(--line);border-radius:20px;padding:17px;margin-bottom:14px;background:#fff;box-shadow:0 8px 22px rgba(15,23,42,.04)}.question h3{font-size:1rem;margin:0 0 12px}.options{display:grid;gap:9px}.option{width:100%;text-align:left;border-radius:14px;padding:10px 12px;display:flex;gap:10px;align-items:flex-start}.option span{display:inline-grid;place-items:center;min-width:25px;height:25px;border-radius:50%;background:#eef2ff;color:#1d4ed8;font-weight:1000}.option.correct{background:#ecfdf3;border-color:#86efac;color:#065f46}.option.wrong{background:#fff7ed;border-color:#fdba74;color:#9a3412}.answer{margin-top:10px;padding:10px 12px;border-left:4px solid var(--brand);background:#eff6ff;border-radius:10px;display:none}.answer.show{display:block}#score{font-weight:1000;color:var(--brand)}#topBtn{position:fixed;right:18px;bottom:18px;border-radius:999px;width:48px;height:48px;box-shadow:var(--shadow)}mark{background:#fef08a;border-radius:4px;padding:0 2px}@media(max-width:1050px){.hero{grid-template-columns:1fr}.page-body.pro{grid-template-columns:1fr}.sticky-original{position:relative;top:0}.section-head{display:block}nav{display:none}}@media(max-width:560px){.page-head{display:block}.page-head .btn{display:inline-block;margin-top:12px}.definition-grid{grid-template-columns:1fr}.hero h2{font-size:2.15rem}}

/* Quiz retry controls */
.question-top{display:flex;justify-content:space-between;gap:14px;align-items:flex-start;margin-bottom:12px}.question-top h3{margin:0;flex:1}.retry-btn{white-space:nowrap;border-color:#bfdbfe;background:#eff6ff;color:#1d4ed8;padding:8px 12px;border-radius:999px;font-size:.88rem;box-shadow:none}.retry-btn:hover{background:#dbeafe}.retry-btn[hidden]{display:none!important}.question.is-wrong{border-color:#fed7aa;box-shadow:0 10px 28px rgba(251,146,60,.12)}.question.is-correct{border-color:#bbf7d0;box-shadow:0 10px 28px rgba(34,197,94,.10)}@media(max-width:560px){.question-top{display:block}.retry-btn{margin-top:10px}}

/* v3 layout: separated study, quiz, and original pages */
nav a.active{color:var(--brand);background:#eef4ff;border:1px solid #dbeafe;border-radius:999px;padding:8px 12px}
.head-actions,.original-page-head>div:last-child{display:flex;gap:8px;flex-wrap:wrap;justify-content:flex-end}.page-body.study-full{padding:22px;background:linear-gradient(180deg,#fff,#f8fafc)}.study-only .study-pane{max-width:1180px;margin:0 auto;width:100%}.study-only .page-card{scroll-margin-top:92px}.study-hero-card{font-size:1.02rem}.visual-cards{background:linear-gradient(135deg,#ffffff,#f8fbff)}.key-facts{background:linear-gradient(135deg,#fff,#fff7ed)}
.quiz-page{padding-top:20px}.quiz-panel{max-width:1180px;margin-inline:auto}.quiz-sticky{position:sticky;top:75px;z-index:15;display:grid;grid-template-columns:repeat(3,minmax(120px,1fr)) auto;gap:12px;align-items:stretch;margin:-4px 0 24px;padding:12px;background:rgba(239,246,255,.92);backdrop-filter:blur(14px);border:1px solid #bfdbfe;border-radius:24px;box-shadow:0 14px 40px rgba(30,64,175,.14)}.score-card{background:#fff;border:1px solid #dbeafe;border-radius:18px;padding:10px 14px;box-shadow:0 6px 16px rgba(15,23,42,.05)}.score-card span{display:block;font-size:.76rem;text-transform:uppercase;letter-spacing:.12em;color:#64748b;font-weight:1000}.score-card strong{font-size:1.65rem;line-height:1.1;color:var(--brand)}.quiz-actions{display:flex;gap:8px;align-items:center;justify-content:flex-end;flex-wrap:wrap}.question{scroll-margin-top:170px}.question h3{font-size:1.08rem}.option:not(:disabled):hover{transform:translateY(-1px);box-shadow:0 8px 18px rgba(15,23,42,.08)}.option{transition:.15s transform,.15s box-shadow,.15s background}
.original-tools{position:sticky;top:75px;z-index:12;background:rgba(255,255,255,.92);backdrop-filter:blur(14px);padding:12px;border:1px solid var(--line);border-radius:20px;box-shadow:0 10px 30px rgba(15,23,42,.08)}.original-jump{display:flex;gap:8px;flex-wrap:wrap;margin:0 0 20px}.original-jump button{border-left:5px solid var(--chap);font-size:.86rem;padding:8px 10px}.original-pages{display:grid;gap:28px}.original-page-card{border:1px solid var(--line);border-top:6px solid var(--chap);border-radius:26px;overflow:hidden;background:#fff;box-shadow:0 18px 48px rgba(15,23,42,.09);scroll-margin-top:155px}.original-page-head{display:flex;justify-content:space-between;gap:16px;align-items:center;padding:16px 18px;background:linear-gradient(90deg,#fff,#f8fafc);border-bottom:1px solid var(--line)}.original-page-head h3{margin:0;font-size:1.1rem}.original-page-head small{color:var(--muted);font-weight:900}.original-page-card img{display:block;width:min(100%,900px);margin:0 auto;background:#fff}.original-page-card:hover{box-shadow:0 22px 58px rgba(15,23,42,.13)}
@media(max-width:900px){.quiz-sticky{grid-template-columns:repeat(3,1fr)}.quiz-actions{grid-column:1/-1;justify-content:stretch}.quiz-actions button{flex:1}.original-page-head{display:block}.original-page-head>div:last-child{justify-content:flex-start;margin-top:10px}.head-actions{justify-content:flex-start;margin-top:12px}.topbar{align-items:flex-start;gap:12px}.topbar nav{display:flex;flex-wrap:wrap}.brand p{display:none}}
@media(max-width:560px){.quiz-sticky{top:82px;grid-template-columns:1fr 1fr 1fr;border-radius:18px;padding:8px}.score-card{padding:8px}.score-card span{font-size:.65rem}.score-card strong{font-size:1.15rem}.quiz-actions{grid-column:1/-1}.original-tools{top:82px}.original-page-card{scroll-margin-top:210px}.topbar{position:relative}.quiz-sticky,.original-tools{top:0}.hero{padding:38px 16px}.stats{grid-template-columns:1fr 1fr 1fr}.stats div{padding:14px}.stats strong{font-size:1.5rem}}
@media(max-width:1050px){nav{display:flex;flex-wrap:wrap}.topbar{gap:14px}}

/* Fix requested: Study page keeps original PDF page beside study material */
.study-only .page-body.study-with-original{display:grid;grid-template-columns:minmax(330px,470px) minmax(0,1fr);gap:24px;padding:22px;background:linear-gradient(180deg,#fff,#f8fafc)}
.study-only .page-body.study-with-original .study-pane{max-width:none;margin:0;width:100%}
.study-only .original-pane{display:block}
.study-only .sticky-original{position:sticky;top:92px}
.study-only .page-img{width:100%;border-radius:20px;border:1px solid var(--line);box-shadow:0 16px 38px rgba(15,23,42,.16);background:#fff}
.study-only .quick{display:flex;gap:8px;flex-wrap:wrap;margin-top:12px}
.study-only .linkpill{display:inline-block;color:#1d4ed8;text-decoration:none}
@media(max-width:1050px){.study-only .page-body.study-with-original{grid-template-columns:1fr}.study-only .sticky-original{position:relative;top:0}.study-only .original-pane{max-width:720px;margin:0 auto;width:100%}}