:root{color-scheme:light;--paper:#f7f5ef;--ink:#24372f;--muted:#57685f;--green:#2f654a;--light:#e4eee5;--line:#ccd7ca;--warm:#fcf0d6;font-family:-apple-system,BlinkMacSystemFont,"PingFang SC","Microsoft YaHei",sans-serif;font-size:20px}
*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:110px}body{margin:0;background:var(--paper);color:var(--ink);line-height:1.8}button,textarea{font:inherit}button,a,summary{touch-action:manipulation}button,summary{cursor:pointer}button{border:1px solid var(--line);background:#fff;color:var(--ink);border-radius:12px;min-height:48px;padding:9px 16px;line-height:1.5}button:hover{border-color:var(--green);background:#edf4ed}button:disabled{opacity:.6;cursor:default}button[aria-pressed=true],button.primary{background:var(--green);border-color:var(--green);color:white}a{color:var(--green);text-underline-offset:4px}a:hover{color:#143b27}button:focus-visible,a:focus-visible,summary:focus-visible,textarea:focus-visible,[tabindex]:focus-visible{outline:3px solid #bf7223;outline-offset:4px}p{margin:0 0 1em}h1,h2,h3,h4{line-height:1.45;margin:0 0 .6em}h1{font-size:clamp(2.3rem,5vw,3.7rem);letter-spacing:.04em}h2{font-size:1.55rem}h3{font-size:1.15rem}h4{font-size:1rem}ul,ol{padding-left:1.5em}li{margin-bottom:.5em}img,svg{max-width:100%}[hidden]{display:none!important}.small{font-size:.8rem;color:var(--muted)}.skip{position:fixed;top:-90px;background:#fff;z-index:50;padding:12px}.skip:focus{top:10px}.topbar{max-width:1440px;margin:auto;padding:22px 32px;display:flex;align-items:center;justify-content:space-between;gap:20px;font-size:.85rem;border-bottom:1px solid var(--line)}.topbar a{padding:8px 0;min-height:48px;display:inline-flex;align-items:center}main{max-width:1440px;margin:auto;padding:0 32px}.hero{max-width:1040px;padding:55px 0 32px}.eyebrow{text-transform:uppercase;font-size:.8rem;letter-spacing:.12em;color:var(--green);font-weight:700;margin-bottom:12px}.hero-question{font-size:1.55rem;font-weight:650;line-height:1.65}.intro{max-width:850px;color:var(--muted);font-size:1.05rem}.learning-map{display:grid;grid-template-columns:repeat(3,1fr);gap:16px;margin:30px 0}.learning-map div{border-top:3px solid var(--green);padding:15px 0;display:flex;flex-direction:column}.learning-map span{font-size:.85rem;color:var(--muted)}.reading-hint{font-size:.85rem;color:var(--muted)}.reading-toolbar{position:sticky;top:0;z-index:10;background:rgba(247,245,239,.98);border-block:1px solid var(--line);display:flex;gap:18px;align-items:center;justify-content:space-between;padding:12px 0}.view-switch{display:flex;gap:8px}.reading-toolbar p{font-size:.8rem;margin:0}.source-jump{font-size:.85rem;white-space:nowrap}.reading-layout{display:grid;grid-template-columns:252px minmax(0,1fr);gap:40px;padding:32px 0 50px}.contents{min-width:0}.contents details{position:sticky;top:104px}.contents summary{font-weight:700;font-size:1rem;min-height:48px;padding:8px 0}.contents summary span{font-size:.75rem;font-weight:400;color:var(--muted);margin-left:10px}.contents nav{display:grid;gap:6px;margin-top:12px}.nav-lesson{border-color:transparent;background:transparent;border-radius:8px;text-align:left;font-size:.8rem;padding:9px 10px;display:flex;gap:10px;align-items:baseline;line-height:1.6;width:100%}.nav-lesson[aria-current=page]{background:var(--light);border-color:var(--line);font-weight:700}.nav-number{color:var(--green);flex:0 0 1.4em}.nav-read{font-size:.7rem;color:var(--green);margin-left:auto;white-space:nowrap}.final-jump{display:block;font-size:.85rem;padding:12px 10px}.reading{min-width:0}.lesson{scroll-margin-top:0;max-width:930px;margin:0 auto 55px;background:#fff;border:1px solid var(--line);border-radius:22px;overflow:hidden}.lesson-header{padding:30px 34px 24px;background:#f0f4ec;border-bottom:1px solid var(--line)}.lesson-number{font-size:.8rem;color:var(--green);margin-bottom:10px}.lesson-subtitle{color:var(--muted);margin-bottom:14px}.lesson-goals{font-size:.9rem;margin:0;padding-left:1.25em}.lesson-main{padding:28px 34px}.dialogue-block{display:flex;gap:12px;margin-bottom:20px;align-items:flex-start}.avatar{background:#e5ecdf;border-radius:50%;width:42px;height:42px;flex:0 0 42px;display:flex;align-items:center;justify-content:center;font-size:.75rem;font-weight:700;color:var(--green);margin-top:4px}.bubble{border-radius:0 16px 16px 16px;padding:15px 20px;background:#f3f5f0;flex:1;min-width:0;white-space:pre-line}.bubble p{margin:0}.dialogue-block.knowledge .bubble{background:var(--warm);border-left:4px solid #d49b3c}.dialogue-block.example .bubble{background:#edf3f8}.block-label{font-size:.7rem;display:block;color:var(--muted);font-weight:700;margin-bottom:6px}.continue-row{border:1px dashed var(--line);border-radius:14px;padding:16px;display:flex;gap:12px;flex-wrap:wrap;align-items:center;margin-bottom:24px}.continue-row p{width:100%;font-size:.8rem;color:var(--muted);margin:0}.section-label{font-size:.75rem;color:var(--green);letter-spacing:.1em;font-weight:700}.activity,.knowledge-summary,.self-explain,.book-link{margin-top:30px;padding-top:24px;border-top:1px solid var(--line)}.activity-guide{font-size:.9rem}.activity-guide ol{margin:10px 0}.observation{background:#f2f5ef;border-radius:12px;padding:16px 18px;margin-top:18px;font-size:.9rem}.observation p:last-child{margin-bottom:0}.diagram{margin:28px 0;padding:20px;background:#f6f7f2;border:1px solid var(--line);border-radius:16px}.diagram figcaption{font-size:.9rem;font-weight:700;margin-bottom:16px}.diagram-nodes{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}.diagram-node{background:#fff;border-radius:10px;padding:12px;font-size:.9rem;border:1px solid var(--line)}.diagram-node span{display:block;font-size:.8rem;color:var(--muted)}.diagram-edges{font-size:.8rem;margin-bottom:0}.diagram-edges li{margin-bottom:8px}.questions{margin-top:34px}.question{margin:22px 0 32px;padding:22px;border:1px solid var(--line);border-radius:16px;background:#fff;min-width:0}.question legend{font-weight:700;padding:0 6px;line-height:1.7;max-width:100%}.question-options{display:grid;gap:10px}.answer{width:100%;text-align:left;background:#f7f8f4;display:flex;gap:12px;align-items:baseline}.option-letter{font-size:.8rem;font-weight:700;color:var(--green);flex:0 0 1.5em}.answer[aria-pressed=true] .option-letter{color:inherit}.answer-reason{border-left:4px solid #bc9146;background:#fff5e3;padding:16px;margin:16px 0 0;white-space:pre-line}.answer-reason.correct{border-color:var(--green);background:#eaf2e7}.self-explain textarea,.chapter-note textarea{display:block;width:100%;padding:14px;border:1px solid #94a995;border-radius:12px;background:#fffef9;resize:vertical;min-height:120px;line-height:1.8;color:var(--ink)}details{margin:18px 0}summary{min-height:48px;line-height:1.65;padding:8px 0;font-weight:650}details>p{margin-top:14px}.reference-answer{padding:16px;background:#f4f5ee;border-radius:12px;white-space:pre-line}.knowledge-summary{background:#f0f5ec;padding:20px;border:0;border-radius:14px}.knowledge-summary ul{margin-bottom:0}.math{background:#fbf6eb;border:1px solid #e2d9c1;border-radius:14px;padding:8px 18px}.formula{font-family:ui-monospace,SFMono-Regular,monospace;white-space:pre-wrap;overflow-wrap:anywhere;line-height:1.8;padding:12px;background:#fff;font-size:.85rem;border-radius:8px}.book-link{font-size:.85rem;color:var(--muted)}.book-link p:last-child{margin-bottom:0}.lesson-footer{padding:20px 34px;background:#f6f7f2;display:flex;justify-content:space-between;flex-wrap:wrap;gap:10px}.lesson-footer button{font-size:.9rem}.quiet{background:transparent;font-size:.85rem}.end-section{max-width:930px;margin:0 0 48px auto;padding:30px 34px;background:#fff;border:1px solid var(--line);border-radius:22px;scroll-margin-top:0}.chapter-note{border-top:1px solid var(--line);padding-top:20px;margin-top:24px}.source-row{padding:16px 0;border-bottom:1px solid var(--line);font-size:.85rem}.source-row p{margin:0 0 6px}.source-row .source-links{display:flex;flex-wrap:wrap;gap:6px}.source-row button{font-size:.8rem;padding:6px 12px}.bibliography{font-size:.8rem;overflow-wrap:anywhere;line-height:1.8}.sources details{border-top:1px solid var(--line);padding-top:12px;font-size:.85rem}footer{max-width:1440px;margin:auto;border-top:1px solid var(--line);padding:28px 32px 45px;font-size:.8rem;color:var(--muted)}footer p{margin-bottom:4px}#clear-confirm{display:block;margin-top:12px}#clear-confirm button{margin:6px}.lesson-open-all{font-size:.85rem}.lesson-citation{font-size:.8rem}.error-message{padding:25px;background:#fff1de;border-radius:12px}
@media(min-width:1200px){.end-section{margin-right:calc((100% - 292px - min(930px,100% - 292px))/2)}}@media(max-width:1000px){main{padding:0 22px}.reading-layout{grid-template-columns:210px minmax(0,1fr);gap:24px}.lesson-main,.lesson-header{padding:24px}.lesson-footer{padding:20px 24px}.nav-lesson{font-size:.75rem}.end-section{max-width:none;margin-left:234px;padding:26px}.topbar{padding:14px 22px}.reading-toolbar{gap:10px}.reading-toolbar p{max-width:175px}}
@media(max-width:760px){:root{font-size:20px}html{scroll-padding-top:140px}.topbar{padding:8px 16px;gap:8px;font-size:.7rem;flex-wrap:wrap}.topbar span{order:3;width:100%}main{padding:0 14px}.hero{padding:30px 4px 20px}.hero-question{font-size:1.2rem}.intro{font-size:1rem}.learning-map{gap:8px;margin:22px 0}.learning-map div{padding:10px 0}.learning-map b{font-size:.85rem}.learning-map span{font-size:.7rem}.reading-hint{font-size:.8rem}.reading-toolbar{flex-wrap:wrap;padding:10px 0;gap:6px 12px}.view-switch{width:100%}.view-switch button{flex:1;padding:8px 10px;font-size:.9rem}.reading-toolbar p{font-size:.7rem;max-width:none}.source-jump{font-size:.7rem;margin-left:auto}.reading-layout{display:block;padding-top:12px}.contents details{position:static;border-bottom:1px solid var(--line);margin-top:0;padding:0 4px 12px}.contents nav{grid-template-columns:1fr}.nav-lesson{font-size:.85rem}.contents{margin-bottom:22px}.lesson{border-radius:17px;margin-bottom:32px;scroll-margin-top:0}.lesson-header{padding:22px 18px}.lesson-main{padding:22px 16px}.lesson h2{font-size:1.35rem}.lesson-goals{font-size:.85rem}.dialogue-block{gap:8px}.avatar{width:32px;height:32px;flex-basis:32px;font-size:.65rem}.bubble{padding:13px 14px}.continue-row{padding:12px;gap:8px}.continue-row button{width:100%}.diagram{padding:14px}.diagram-nodes{grid-template-columns:1fr}.diagram-node{font-size:.85rem}.question{padding:14px 12px;margin:20px 0 30px}.answer{padding:12px;font-size:.95rem;gap:4px}.option-letter{flex-basis:1.3em}.answer-reason{padding:13px;font-size:.95rem}.lesson-footer{padding:16px;display:grid;grid-template-columns:1fr}.end-section{margin-left:0;padding:24px 18px;border-radius:17px;scroll-margin-top:0}.end-section h2{font-size:1.3rem}.book-link{font-size:.8rem}.reading-layout .lesson:last-child{margin-bottom:0}.sources{font-size:.9rem}.learning-map div:last-child{min-width:0}footer{padding:24px 18px}.self-explain textarea,.chapter-note textarea{font-size:1rem}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*::before,*::after{animation:none!important;transition:none!important}}@media print{.topbar,.reading-toolbar,.contents,.continue-row,.lesson-footer,footer,.question-options,.fbw button{display:none!important}.reading-layout{display:block}.end-section{margin-left:0}.lesson{break-inside:avoid;border-color:#aaa}.reading{width:100%}details{display:block}main{padding:0}.hero{padding-top:0}:root{font-size:12pt}.bubble{background:#fff}.avatar{display:none}.answer-reason{display:block}.reading-layout{padding:0}}

.reading[data-view="read"] .avatar{display:none}.reading[data-view="read"] .bubble{border-radius:14px}.reading[data-view="read"] .dialogue-block{display:block}
