:root{--paper:#f8f6f0;--ink:#26372e;--forest:#234c3a;--muted:#7c8279;--rule:#d8d9ce;--accent:#aa583e;--wash:#eeeee4;--sidebar:250px;--reading:780px}
*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:100px}body{margin:0;background:radial-gradient(ellipse at 90% 0,#e8eadd66,transparent 52%),var(--paper);color:var(--ink);font-family:"Songti SC","STSong","Noto Serif CJK SC",serif;font-size:17px;line-height:1.95}a{color:inherit;text-decoration:none}button{font:inherit;cursor:pointer}button:focus-visible,a:focus-visible,summary:focus-visible{outline:3px solid #bd7e36;outline-offset:4px}.skip{position:fixed;top:-60px;background:var(--ink);color:white;padding:8px 20px;z-index:99}.skip:focus{top:0}.reading-progress{position:fixed;top:0;left:0;height:3px;background:var(--accent);z-index:50}.sidebar{position:fixed;width:var(--sidebar);inset:0 auto 0 0;padding:44px 28px;background:#edf0e7;border-right:1px solid var(--rule);display:flex;flex-direction:column;overflow:auto}.brand{font-size:25px;letter-spacing:3px;font-weight:700;line-height:1.5}.brand span{display:block;font-size:11px;letter-spacing:2px;font-weight:400;margin-top:7px;color:#657366}.volume-label{font-size:11px;letter-spacing:1px;margin-top:58px;color:#647561}.spine-number{font-size:76px;line-height:1.2;letter-spacing:-5px;font-weight:400;color:var(--forest);margin:14px 0 27px}nav{display:grid;gap:4px}nav a{display:block;padding:10px 0;font-size:14px;line-height:1.6;border-bottom:1px solid #d9dfd3}nav a span{font-size:11px;margin-right:12px;color:#83917e}nav a:hover,nav a.active{color:var(--accent)}nav a.active{font-weight:bold}.sidebar-foot{margin-top:auto;padding-top:52px;font-size:11px;line-height:2;color:#7c8876}.book-shell{margin-left:var(--sidebar)}.toolbar{position:sticky;top:0;z-index:20;background:#f8f6f0f5;backdrop-filter:blur(12px);border-bottom:1px solid var(--rule);min-height:68px;padding:12px 30px;display:flex;gap:16px;align-items:center;justify-content:space-between;font-size:12px;font-family:"PingFang SC",sans-serif}.toolbar-label{white-space:nowrap;color:var(--forest);font-weight:600}.subtle{color:#9a9f93;font-weight:400}.controls{display:flex;gap:10px;align-items:center;flex-wrap:wrap}.controls button,.mode-link{border:1px solid #bdc5b6;border-radius:2px;background:transparent;padding:7px 11px;font-size:12px;color:var(--forest);line-height:1.5}.controls button:hover,.mode-link:hover{background:#e8ece0}.controls button[aria-pressed=true]{background:var(--forest);color:white}.package-link{padding:4px;color:#6a7562}.student-tag{font-size:12px;color:var(--forest)}main{max-width:calc(var(--reading) + 100px);margin:0 auto;padding:0 50px 72px}.chapter-cover{position:relative;padding:65px 0 48px;border-bottom:2px solid var(--ink);animation:reveal .6s ease-out}.eyebrow{font-family:"PingFang SC",sans-serif;font-size:10px;letter-spacing:1.8px;color:var(--accent);font-weight:600}.edition{font-size:12px;color:var(--muted);margin:20px 0}h1{font-size:clamp(38px,4.3vw,62px);line-height:1.4;letter-spacing:1px;font-weight:700;margin:16px 0 23px}.cover-dot{color:var(--accent)}.cover-deck{font-size:16px;line-height:1.9;color:#737b6b;max-width:500px}.chapter-meta{display:flex;gap:24px;flex-wrap:wrap;font-family:"PingFang SC",sans-serif;font-size:11px;color:#79816f;margin-top:30px}.section-heading{display:flex;gap:22px;align-items:flex-start;border-top:1px solid var(--ink);padding-top:28px;margin:76px 0 32px;scroll-margin-top:90px}.section-number{font-size:37px;line-height:1.6;color:#a7afa0;font-weight:400}.section-heading h2{font-size:29px;margin:0;line-height:1.7;letter-spacing:1px}.section-heading p{margin:6px 0 0;color:var(--muted);font-size:13px}.group-heading{font-size:21px;margin:45px 0 24px;padding:0 0 13px;border-bottom:1px solid var(--rule)}.prose p{margin:18px 0}.prose h2,.prose h3{font-size:22px;margin:30px 0 18px}.prose img,.question img,.teacher img{display:block;max-width:100%;max-height:330px;width:auto;height:auto;margin:22px auto;mix-blend-mode:multiply}.provenance{font-family:"PingFang SC",sans-serif;font-size:10px;line-height:1.6;color:#89917f;margin:12px 0 22px;letter-spacing:.1px}.provenance a:hover{text-decoration:underline;color:var(--forest)}.teacher,.editor,.intro{padding:24px 27px;margin:30px 0;border-left:3px solid var(--forest);background:#ecefe5}.teacher h3,.editor h3,.intro h3{font-size:17px;line-height:1.6;margin:6px 0 16px}.teacher p,.editor p,.intro p{font-size:15px;line-height:1.95;margin:14px 0}.editor{border-left-color:var(--accent);background:#f1e9de}.intro{margin-top:33px;background:transparent;border-left:1px solid var(--accent);padding:3px 24px}.intro .eyebrow{display:none}.intro p{color:#69715f}.question{margin:31px 0 43px;scroll-margin-top:90px}.question-label{font-size:12px;letter-spacing:1px;color:var(--accent);font-family:"PingFang SC",sans-serif;font-weight:600;margin-bottom:12px}.question-body{border-left:2px solid #d3b59b;padding:1px 0 1px 22px}.question-body>p:first-child{margin-top:0}.question-body>p:last-child{margin-bottom:0}.question-body p{margin:15px 0}.question-body ol{padding-left:22px}.answer{margin:18px 0 0;background:#eeeee5;border:1px solid #e1e2d7}.answer summary{padding:10px 17px;font-size:12px;color:#526449;cursor:pointer;font-family:"PingFang SC",sans-serif;list-style-position:inside}.answer summary span{float:right;color:#8e9684;font-size:10px}.answer-body{padding:3px 21px 13px;font-size:16px;line-height:1.95;border-top:1px solid #e0e3d6}.question-analysis{margin:14px 0 0;padding:10px 18px;border-left:2px solid #b1be9f}.question-analysis p{font-size:14px;line-height:1.9;margin:8px 0}.question-analysis .provenance{margin-bottom:6px}.question-analysis .eyebrow{color:#71805f}.math.display{max-width:100%;overflow-x:auto;overflow-y:hidden;padding:5px 0;margin:15px 0}.math:not(.display){overflow-wrap:normal}.katex{font-size:1.04em}.katex-display{margin:.35em 0}.katex-render-error{color:#b3261e;border:1px solid #b3261e}.book-footer{border-top:2px solid var(--ink);margin-top:64px;padding-top:20px;font-size:12px;color:#838a7a}.book-footer a{display:inline-block;margin-top:20px;color:var(--forest)}.answers-hidden .answer,.answers-hidden .question-analysis,.notes-hidden .teacher-only{display:none!important}#status{position:fixed;bottom:25px;left:calc(50% + var(--sidebar)/2);transform:translateX(-50%) translateY(12px);background:var(--forest);color:white;border-radius:3px;padding:10px 20px;font:13px/1.6 "PingFang SC",sans-serif;opacity:0;pointer-events:none;transition:.2s;z-index:40;max-width:90vw;white-space:normal}#status.visible{opacity:1;transform:translateX(-50%) translateY(0)}
.key-point{--key-ink:#365542;--key-wash:#e8eee4;margin:28px 0;padding:22px 26px 16px;border:1px solid #ccd5c5;border-left:5px solid var(--key-ink);background:linear-gradient(115deg,var(--key-wash),#f9f8f1);scroll-margin-top:100px;break-inside:avoid}.key-label{font:600 11px/1.6 "PingFang SC",sans-serif;letter-spacing:1.5px;color:var(--key-ink)}.prose .key-point h3{margin:7px 0 17px;font-size:19px;line-height:1.65;color:var(--key-ink)}.prose .key-point p{margin:13px 0}.key-method{--key-ink:#3e6372;--key-wash:#e6edf0;border-color:#c6d3d9;border-left-color:var(--key-ink)}.key-condition{--key-ink:#8b512b;--key-wash:#f2e5d3;border-color:#ddc9af;border-left-color:var(--key-ink)}.key-concept{--key-ink:#625d3e;--key-wash:#eeecd9;border-color:#d6d2ba;border-left-color:var(--key-ink)}.key-point .math.display{margin:13px 0}.key-point .katex{color:var(--ink)}
@media(max-width:720px){.key-point{padding:18px 16px 12px;margin:24px 0}.prose .key-point h3{font-size:17px}.key-label{font-size:10px;letter-spacing:1px}}
@keyframes reveal{from{opacity:0;transform:translateY(12px)}to{opacity:1;transform:none}}
@media(min-width:1500px){:root{--sidebar:290px;--reading:820px}.sidebar{padding-left:40px}.toolbar{padding-left:45px;padding-right:45px}}
@media(max-width:1000px){:root{--sidebar:210px}.sidebar{padding:32px 22px}.toolbar{padding:10px 18px;align-items:flex-start}.toolbar-label{padding-top:8px}.controls{justify-content:flex-end;gap:6px}main{padding:0 32px 60px}.package-link{display:none}}
@media(max-width:720px){:root{--sidebar:0px}.sidebar{position:relative;width:auto;height:auto;padding:22px 22px 14px;border-right:0;border-bottom:1px solid var(--rule);display:block}.brand{font-size:20px;letter-spacing:2px}.brand span{display:inline;margin-left:13px;font-size:10px;letter-spacing:1px}.volume-label,.spine-number,.sidebar-foot{display:none}nav{display:flex;overflow-x:auto;gap:20px;margin-top:15px;padding-bottom:4px}nav a{white-space:nowrap;padding:5px 0;border:0;font-size:12px}nav a span{margin-right:5px;font-size:10px}.book-shell{margin-left:0}.toolbar{min-height:62px;padding:10px 16px;gap:8px}.toolbar-label{display:none}.controls{justify-content:flex-start;gap:6px}.controls button,.mode-link{font-size:11px;padding:7px 9px}main{padding:0 22px 45px}.chapter-cover{padding:40px 0 30px}h1{font-size:39px}.cover-deck{font-size:14px}.chapter-meta{font-size:10px;gap:15px}.section-heading{gap:14px;margin-top:52px}.section-heading h2{font-size:25px}.section-number{font-size:31px}.section-heading p{font-size:11px}.teacher,.editor{padding:19px 18px}.teacher p,.editor p{font-size:14px}.question-body{padding-left:15px}.answer-body{padding-left:16px;padding-right:16px;font-size:15px}body{font-size:16px}.katex{font-size:1em}.prose img,.question img{max-height:280px}#status{left:50%;font-size:12px;width:max-content;max-width:90vw}.prose,.question,.teacher{overflow-wrap:anywhere}.math .katex{overflow-wrap:normal}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*::before,*::after{animation:none!important;transition:none!important}}
/* Keep the established book palette while spending more of each screen on content. */
@media screen{
body:not(.spacious){--sidebar:228px;--reading:900px;line-height:1.78}
body:not(.spacious) .sidebar{padding:30px 23px}
body:not(.spacious) .volume-label{margin-top:32px}
body:not(.spacious) .spine-number{font-size:58px;margin:8px 0 18px}
body:not(.spacious) main{max-width:calc(var(--reading) + 64px);padding:0 32px 48px}
body:not(.spacious) .chapter-cover{padding:28px 0 22px}
body:not(.spacious) .edition{margin:10px 0}
body:not(.spacious) h1{font-size:42px;line-height:1.4;margin:12px 0 10px}
body:not(.spacious) .chapter-cover br{display:none}
body:not(.spacious) .cover-deck{margin:8px 0;font-size:15px;max-width:none}
body:not(.spacious) .chapter-meta{margin-top:14px;gap:20px}
body:not(.spacious) .section-heading{padding-top:16px;margin:36px 0 20px;gap:16px}
body:not(.spacious) .section-heading h2{font-size:26px;line-height:1.5}
body:not(.spacious) .section-heading p{margin:3px 0 0}
body:not(.spacious) .section-number{font-size:30px;line-height:1.4}
body:not(.spacious) .group-heading{margin:25px 0 14px;padding-bottom:8px}
body:not(.spacious) .prose p{margin:12px 0}
body:not(.spacious) .prose h2,body:not(.spacious) .prose h3{margin:20px 0 12px}
body:not(.spacious) .prose img,body:not(.spacious) .question img,body:not(.spacious) .teacher img{margin:14px auto;max-height:270px}
body:not(.spacious) .provenance{margin:6px 0 10px}
body:not(.spacious) .teacher,body:not(.spacious) .editor,body:not(.spacious) .intro{padding:15px 19px;margin:18px 0}
body:not(.spacious) .teacher p,body:not(.spacious) .editor p,body:not(.spacious) .intro p{line-height:1.78;margin:9px 0}
body:not(.spacious) .question{margin:20px 0 26px}
body:not(.spacious) .question-label{margin-bottom:8px}
body:not(.spacious) .question-body p{margin:11px 0}
body:not(.spacious) .answer{margin-top:12px}
body:not(.spacious) .answer summary{padding:7px 14px}
body:not(.spacious) .answer-body{padding:2px 17px 9px;line-height:1.78}
body:not(.spacious) .answer-body p{margin:11px 0}
body:not(.spacious) .question-analysis{margin-top:10px;padding:7px 15px}
body:not(.spacious) .key-point{margin:18px 0;padding:15px 19px 10px}
body:not(.spacious) .key-point h3{margin:5px 0 10px;font-size:18px}
body:not(.spacious) .key-point p{margin:9px 0}
body:not(.spacious) .math.display{margin:9px 0;padding:2px 0}
body:not(.spacious) .book-footer{margin-top:36px}
body:not(.spacious) .toolbar{min-height:58px;padding:10px 22px;gap:10px}
body:not(.spacious) .controls{gap:7px}
}
dialog{width:min(590px,calc(100vw - 28px));max-height:88vh;padding:26px;border:1px solid #bdc5b6;border-radius:5px;background:var(--paper);color:var(--ink);box-shadow:0 20px 80px #1b322938;font-family:"PingFang SC",sans-serif;line-height:1.7}
dialog::backdrop{background:#203a2a70;backdrop-filter:blur(3px)}
.dialog-heading{display:flex;align-items:flex-start;justify-content:space-between;gap:15px}.dialog-heading h2{margin:3px 0 0;font-size:24px;font-family:"Songti SC",serif}.dialog-heading button{border:0;background:transparent;font-size:26px;line-height:1.2;color:var(--forest)}
.dialog-description,.print-help{font-size:12px;color:#697364;margin:12px 0 18px}dialog fieldset{border:0;border-top:1px solid var(--rule);padding:14px 0;margin:0}dialog legend{padding:0 12px 0 0;font-size:11px;letter-spacing:1px;color:#64745d}.print-modes{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:8px}.print-choice{display:flex;align-items:center;gap:7px;border:1px solid #ccd2c4;padding:9px 12px;font-size:13px;cursor:pointer}.print-choice:has(:checked){border-color:var(--forest);background:#e8eddf}.print-scopes{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:9px 15px;font-size:12px}.print-scopes label,.print-options label{display:flex;gap:7px;align-items:flex-start}.print-options{display:flex;gap:12px;flex-wrap:wrap;font-size:12px;margin:5px 0 12px}input{accent-color:var(--forest)}.scope-actions{display:flex;gap:12px;margin:0 0 10px}.scope-actions button{border:0;background:transparent;padding:0;color:var(--forest);font-size:11px;text-decoration:underline}#print-summary{font-size:12px;color:var(--forest);padding:10px 12px;background:#e9eddf;margin:10px 0}.print-help{font-size:11px;margin-bottom:14px}.dialog-actions{display:flex;justify-content:flex-end;gap:10px}.dialog-actions button,#print-preview-bar button{padding:8px 13px;font-size:12px;border:1px solid #bfc9b6;background:transparent;color:var(--forest)}#print-submit,#print-now{background:var(--forest)!important;color:white!important}button:disabled{opacity:.4;cursor:not-allowed}#print-output,#print-preview-bar{display:none}
body.print-preview .book-shell,body.print-preview .sidebar,body.print-preview .reading-progress{display:none}
body.print-preview #print-preview-bar{display:flex;position:sticky;top:0;z-index:30;align-items:center;justify-content:space-between;gap:10px;padding:12px 24px;background:var(--paper);border-bottom:1px solid var(--rule);font:13px/1.6 "PingFang SC",sans-serif}
#print-preview-bar small{color:var(--muted);font-size:11px}#print-preview-bar>div{display:flex;gap:8px}
body.print-preview #print-output{display:block;width:min(210mm,calc(100% - 32px));margin:22px auto 40px;padding:12mm;background:white;box-shadow:0 4px 30px #243c2915}
#print-output{font-size:10.5pt;line-height:1.5;color:#202720;overflow-wrap:anywhere}#print-output .print-title{border-bottom:1.5px solid #333;padding-bottom:6px;margin-bottom:12px}#print-output .print-title h1{font-size:16pt;line-height:1.4;margin:0 0 5px}#print-output .print-title p{font-size:9pt;margin:0;color:#60665c}#print-output .section-heading{margin:14px 0 8px;padding-top:6px;gap:10px;break-after:avoid}#print-output .section-heading h2{font-size:12.5pt;line-height:1.4}#print-output .section-heading p{display:none}#print-output .section-number{font-size:17pt;line-height:1.2}#print-output .group-heading{font-size:11pt;margin:12px 0 7px;padding-bottom:4px;break-after:avoid}#print-output .prose p,#print-output .question-body p{margin:5px 0}#print-output .prose h2,#print-output .prose h3{font-size:11.5pt;margin:10px 0 6px;break-after:avoid}#print-output .question{margin:10px 0 12px;break-inside:avoid-page;page-break-inside:avoid}#print-output .question-label{font-size:8.5pt;margin-bottom:4px;break-after:avoid;color:#343e31}#print-output .question-body{padding:0;border:0;break-inside:avoid-page}#print-output .print-answer{border-top:1px solid #ccc;margin-top:6px;padding-top:4px;break-inside:auto}#print-output .print-answer h4{font:600 9pt/1.5 "PingFang SC",sans-serif;margin:0 0 5px;break-after:avoid}#print-output .answer-body{font-size:10pt;line-height:1.5;padding:0;border:0}#print-output .answer-body p{margin:5px 0}#print-output .key-point{background:none;padding:7px 10px 5px;margin:9px 0;border-color:#ccc;border-left:3px solid #666;break-inside:avoid}#print-output .key-point h3{font-size:10.5pt;margin:3px 0 6px;color:#303a2c}#print-output .key-label{font-size:8pt;color:#5c6256}#print-output .teacher,#print-output .editor,#print-output .intro,#print-output .print-commentary{background:none;border-left:1px solid #aaa;margin:8px 0;padding:5px 10px;break-inside:auto}#print-output .teacher p,#print-output .editor p,#print-output .print-commentary p{font-size:9.5pt;line-height:1.5;margin:5px 0}#print-output img{max-width:100%;max-height:40mm;margin:6px auto;mix-blend-mode:normal;break-inside:avoid}#print-output .math.display{overflow:visible;margin:5px 0;padding:1px 0;break-inside:avoid}#print-output .katex-display{margin:.1em 0}#print-output p{orphans:2;widows:2}#print-output p:has(>img){break-after:avoid}#print-output .provenance{font-size:7.5pt;color:#666;margin:5px 0 8px}
@media(max-width:720px){
body:not(.spacious){--sidebar:0px;font-size:16px}
body:not(.spacious) .sidebar{padding:17px 20px 10px}
body:not(.spacious) main{padding:0 20px 36px}
body:not(.spacious) .toolbar{padding:8px 12px}
body:not(.spacious) .controls{gap:6px}
body:not(.spacious) h1{font-size:32px}
body:not(.spacious) .chapter-cover{padding:22px 0 18px}
body:not(.spacious) .section-heading{margin-top:29px;gap:12px}
body:not(.spacious) .section-heading h2{font-size:23px}
body:not(.spacious) .teacher,body:not(.spacious) .editor,body:not(.spacious) .key-point{padding:12px 14px}
dialog{padding:20px}.print-scopes{gap:9px;font-size:11px}.print-options{display:grid;gap:7px}
body.print-preview #print-preview-bar{align-items:flex-start;flex-direction:column;padding:9px 12px}#print-preview-bar small{display:none}#print-preview-bar button{padding:7px 10px;font-size:11px}body.print-preview #print-output{width:100%;margin:0;padding:24px 20px;box-shadow:none}
}
.dialog-actions{position:sticky;bottom:-1px;padding:12px 0 2px;background:var(--paper);border-top:1px solid var(--rule);z-index:2}
@page{size:A4;margin:12mm 12mm 13mm}
@media print{
html{scroll-behavior:auto}body{background:white;margin:0}
.sidebar,.book-shell,.reading-progress,#status,#print-dialog,#print-preview-bar,.skip{display:none!important}
body #print-output{display:block!important;width:auto!important;margin:0!important;padding:0!important;box-shadow:none!important}
#print-output a{color:inherit;text-decoration:none}#print-output .print-module{break-inside:auto}#print-output .key-point,#print-output .teacher,#print-output .editor{box-decoration-break:clone;-webkit-box-decoration-break:clone}
}

#print-output .print-question-head{break-inside:avoid-page;page-break-inside:avoid}
/* Contain trailing margins; image-heavy stems need room for every caption. */
#print-output .question{display:flow-root}
#print-output .print-compact-figures .question-body img{max-height:34mm}

/* A compact page index reuses the book's left-hand reading rail. */
@media screen{
html{scroll-padding-top:var(--reader-offset,80px)}
.book-body [id]{scroll-margin-top:12px}
.sidebar,body:not(.spacious) .sidebar{padding-top:24px;padding-bottom:16px;gap:0}
.sidebar .volume-label{margin-top:22px;font-size:10px;line-height:1.6}
.sidebar .spine-number{font-size:36px;letter-spacing:-1px;margin:8px 0 15px}
.sidebar .sidebar-foot{padding-top:14px;font-size:10px;flex-shrink:0}
.toc-tools{font-family:"PingFang SC",sans-serif;flex-shrink:0}
.toc-tools label{display:block;font-size:12px;font-weight:600;color:var(--forest);margin-bottom:8px}
.toc-tools input,.toc-tools select{width:100%;min-width:0;border:1px solid #c4cdbd;border-radius:3px;background:#f9faf5;color:var(--ink);font:11px/1.6 "PingFang SC",sans-serif;padding:7px 8px}
.toc-tools input:focus,.toc-tools select:focus{outline:2px solid var(--forest);outline-offset:1px}
.toc-tools select{margin-top:6px}
#toc-count{font-size:10px;color:#73816c;margin:7px 0;line-height:1.6}
.sidebar .page-toc{display:block;flex:1;min-height:50px;overflow:auto;overscroll-behavior:contain;scrollbar-width:thin;margin:0 -8px 0 -3px;padding:0 8px 0 3px}
.page-toc .toc-link{border:0;border-radius:3px;margin:1px 0;padding:6px 8px;font-size:12px;line-height:1.6;overflow-wrap:anywhere}
.page-toc .toc-link[hidden]{display:none}
.page-toc .toc-section{font-size:13px;font-weight:600;border-top:1px solid #d0dac8;padding-top:10px;margin-top:8px}
.page-toc .toc-section span{margin-right:5px;font-size:10px}
.page-toc .toc-link .toc-title{font-size:inherit;margin-right:0;color:inherit}
.page-toc .toc-heading{color:#596952;font-weight:600}
.page-toc .toc-question{padding-left:17px;font-size:11px;color:#69775f}
.page-toc .toc-preview{display:-webkit-box;margin-top:2px;color:#8a9184;font-size:10px;font-weight:400;line-height:1.45;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden}
.page-toc .toc-key{padding-left:17px;color:#966043;font-size:11px}
.page-toc .toc-link:hover{background:#e3e9db;color:var(--forest)}
.page-toc .toc-link.active{background:#dce6d3;color:#234c3a;box-shadow:inset 2px 0 #aa583e}
#toc-toggle,#toc-dismiss,#toc-backdrop{display:none}
.question-analysis h3,.question-analysis h4{font-size:15px;margin:12px 0 7px}
.answer-body>.question-analysis{border-top:1px solid #d8dfcf;margin-top:16px;padding:12px 0 0;border-left:0}
}
@media screen and (max-width:720px){
.sidebar,body:not(.spacious) .sidebar{position:fixed;inset:0 auto 0 0;z-index:62;width:min(330px,88vw);height:100dvh;display:flex;padding:22px 20px 16px;transform:translateX(-105%);transition:transform .18s ease;box-shadow:10px 0 40px #243c291a}
body.toc-open{overflow:hidden}
body.toc-open .sidebar{transform:translateX(0)}
.sidebar .brand{font-size:21px;padding-right:25px}
.sidebar .brand span{display:block;margin:6px 0 0;font-size:10px}
.sidebar .volume-label,.sidebar .spine-number,.sidebar .sidebar-foot{display:block}
.sidebar .volume-label{margin-top:16px}
.sidebar .spine-number{font-size:28px;margin:6px 0 12px}
.sidebar .page-toc{overflow-x:hidden}
.page-toc .toc-link{white-space:normal}
#toc-toggle{display:inline-block}
#toc-dismiss{display:block;position:absolute;right:8px;top:10px;z-index:2;min-width:44px;min-height:44px;background:var(--paper);border:0;font-size:26px;color:var(--forest);line-height:1;padding:3px 8px}
#toc-backdrop:not([hidden]){display:block;position:fixed;inset:0;z-index:61;background:#172a2355;border:0;backdrop-filter:blur(2px)}
}
@media print{#toc-backdrop,#toc-toggle,#toc-dismiss{display:none!important}}
@media screen{
.chapter-cover .eyebrow,.spine-number,.section-number,.toolbar-label .subtle,.toc-section>span:not(.toc-title){display:none}
.section-heading{gap:0}
.chapter-cover h1{font-family:"Songti SC","STSong","Noto Serif CJK SC",serif;font-weight:600;letter-spacing:0;line-height:1.38;text-wrap:balance}
.chapter-cover .cover-dot{display:none}
.book-body :is(.prose,.question-body,.answer-body,.teacher,.editor,.intro) p{text-align:justify;text-spacing-trim:trim-start;line-height:1.85}
.book-body :is(.prose,.question-body,.answer-body,.teacher,.editor,.intro) p:has(> img){text-align:center}
.page-toc .review-toc-row{display:flex;align-items:center}
.page-toc .review-toc-row>.toc-link{flex:1;min-width:0}
.page-toc .review-toc-toggle{flex:0 0 32px;min-height:32px;border:1px solid #aebfae;border-radius:4px;background:transparent;color:#245b52;font:600 18px/1 sans-serif;cursor:pointer}
.page-toc .review-toc-toggle:focus-visible{outline:3px solid #a97537;outline-offset:2px}
.page-toc .review-toc-group.has-current>.review-toc-row>.toc-link{background:#e5ede0;color:#234c3a;box-shadow:inset 2px 0 #aa583e}
.book-body .question:target{outline:2px solid #9bb8a5;outline-offset:4px}
.book-body .group-heading{color:#9a4b31;border-bottom-color:#d9bca9}
.book-body .section-heading h2{color:#245b52}
.book-body .answer{background:#edf2ef;border-color:#c8d8ce}
.book-body .answer summary{color:#245b52}
}
@media(max-width:720px){
body:not(.spacious) .chapter-cover h1{font-size:clamp(27px,6.8vw,32px);line-height:1.45}
.page-toc .review-toc-toggle{flex-basis:44px;min-height:44px}
}

/* Compact screen reading without changing the separate print layout. */
@media screen{
body:not(.spacious){font-size:16px;line-height:1.68}
body:not(.spacious) .chapter-cover{padding:20px 0 16px}
body:not(.spacious) h1{font-size:36px;line-height:1.3;margin:8px 0}
body:not(.spacious) .edition{margin:6px 0}
body:not(.spacious) .chapter-meta{margin-top:9px}
body:not(.spacious) .section-heading{margin:26px 0 15px;padding-top:12px}
body:not(.spacious) .section-heading h2{font-size:23px}
body:not(.spacious) .section-number{font-size:27px}
body:not(.spacious) .group-heading{margin:20px 0 11px;font-size:19px}
body:not(.spacious) .prose p{margin:9px 0}
body:not(.spacious) .question{margin:16px 0 20px}
body:not(.spacious) .question-label{margin-bottom:5px}
body:not(.spacious) .question-body p{margin:8px 0}
body:not(.spacious) .key-point{margin:14px 0;padding:12px 16px 8px}
body:not(.spacious) .math.display{margin:7px 0}
}
@media screen and (max-width:720px){
body:not(.spacious) main{padding:0 18px 40px}
body:not(.spacious) h1{font-size:30px}
body:not(.spacious) .toolbar{padding:8px 12px}
body:not(.spacious) .section-heading{gap:10px}
}

@media screen{
.teacher-brief{margin:10px 0;font-size:15px;line-height:1.7}
.teacher-brief strong{font:600 12px/1.5 "PingFang SC",sans-serif;color:var(--forest)}
.teacher-brief p{margin:5px 0!important}
.teacher-guidance-source>summary{cursor:pointer;color:var(--forest);font:600 12px/1.6 "PingFang SC",sans-serif}
.teacher-guidance-source[open]>summary{margin-bottom:12px}
.teacher-guidance-source>summary:focus-visible,.reader-more>summary:focus-visible{outline:3px solid #bd7e36;outline-offset:3px}
.toc-preview .katex{font-size:1em}
.reader-more,.reader-more-items{display:contents}
.reader-more>summary{display:none}
}
@media screen and (max-width:720px){
.reader-more{display:block;position:relative}
.controls .student-tag{display:none}
.reader-more>summary{display:block;list-style:none;border:1px solid #bdc5b6;padding:7px 9px;font:11px/1.5 "PingFang SC",sans-serif;color:var(--forest);cursor:pointer}
.reader-more>summary::-webkit-details-marker{display:none}
.reader-more-items{display:grid;position:absolute;right:0;top:calc(100% + 6px);z-index:45;min-width:150px;padding:8px;gap:5px;background:#f8f6f0;border:1px solid #bdc5b6;box-shadow:0 8px 24px #26372e24}
.reader-more-items button,.reader-more-items a{display:block;width:100%;text-align:left;padding:8px 10px}
.reader-more-items .package-link{display:block}
}