:root{color-scheme:light;--paper:#f7f5ef;--ink:#26322f;--muted:#596660;--accent:#a54a2c;--line:#dcded5;--surface:#fffefa}
*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:65px}body{margin:0;background:var(--paper);color:var(--ink);font:16px/1.8 -apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif}a{color:var(--accent);text-underline-offset:3px}header{max-width:1160px;margin:auto;padding:44px 24px 28px}h1{font-size:clamp(29px,4vw,47px);line-height:1.25;letter-spacing:-.02em;margin:12px 0 20px}.kicker{color:var(--accent);font-weight:700;font-size:13px;letter-spacing:.07em}.lede{font-size:18px;max-width:900px;color:var(--muted)}.download{display:inline-block;border:1px solid var(--accent);padding:6px 16px;border-radius:6px;margin-right:14px}.book-layout{display:grid;grid-template-columns:245px minmax(0,1fr);gap:32px;max-width:1160px;margin:0 auto;padding:0 24px 60px}.book-toc{align-self:start;position:sticky;top:65px;max-height:calc(100vh - 85px);overflow:auto;padding:0 14px 14px 0}.book-toc h2{font-size:18px;margin:0 0 12px}.book-toc nav{display:grid;gap:8px}.book-toc nav a{font-size:14px;color:var(--muted);text-decoration:none;line-height:1.5}.book-toc nav a:hover{color:var(--accent)}main{min-width:0;max-width:100%}section{min-width:0}h2{font-size:27px;line-height:1.4;margin:0 0 16px}h3{font-size:23px;line-height:1.4;margin:0 0 20px}h4{font-size:16px;margin:20px 0 8px}p{margin:12px 0;overflow-wrap:anywhere}ol,ul{padding-left:1.4em}li{margin:6px 0}.intro{padding:22px 0 40px}.category{padding:32px 0 0;border-top:2px solid var(--line);scroll-margin-top:65px}.lesson{background:#eee9db;border-left:4px solid var(--accent);padding:16px 20px;margin:18px 0}.question-links{font-size:14px;line-height:2.2;padding-bottom:18px}.problem{padding:28px 0 32px;border-top:1px solid var(--line);scroll-margin-top:65px}.number{display:inline-block;font-size:14px;color:var(--accent);background:#f0e7db;border-radius:5px;padding:3px 8px;vertical-align:middle;margin-right:5px}.example{background:#edf1e9;padding:12px 16px;border-radius:6px}.pitfall{border-left:3px solid #b57e35;padding:10px 15px;background:#faf1df}code{font-family:"SFMono-Regular",Consolas,monospace;font-size:.88em;background:#ecebe5;padding:2px 4px;border-radius:3px}pre{max-width:100%;min-width:0;overflow-x:auto;background:#202b29;color:#f4f3e9;padding:18px;border-radius:8px;line-height:1.6;font-size:13px;tab-size:4}pre code{background:none;color:inherit;padding:0;font-size:inherit;white-space:pre}.source-link{display:flex;justify-content:space-between;gap:12px;font-size:13px;color:var(--muted)}#sources{padding-top:32px;border-top:2px solid var(--line)}.search-tools{display:grid;grid-template-columns:minmax(0,1fr) auto auto;gap:10px;align-items:center;margin:24px 0 0}.search-tools label{grid-column:1/-1;font-size:14px}.search-tools input{min-width:0;width:100%;border:1px solid var(--line);padding:10px;font:inherit;border-radius:5px;background:var(--surface)}.search-tools output{font-size:13px}.search-tools button{border:1px solid var(--line);padding:10px;background:var(--surface);border-radius:5px;color:var(--ink)}[hidden]{display:none!important}
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@media print{@page{size:A4;margin:15mm 14mm 17mm}html,body{background:white;font-size:10pt;line-height:1.6;scroll-behavior:auto}header{max-width:none;padding:0 0 12pt}.notes-sitebar,.book-toc,.search-tools,.source-link,.download,header>p:last-child{display:none!important}.book-layout{display:block;max-width:none;padding:0}main{display:block;max-width:none}h1{font-size:25pt}h2{font-size:19pt}h3{font-size:15pt}h4{font-size:11pt}h2,h3,h4{break-after:avoid-page}p,li{orphans:3;widows:3}.category{break-before:page;padding-top:0;border:0}.problem{display:block!important;padding:18pt 0 14pt;overflow:visible}.category[hidden],.problem[hidden]{display:block!important}.lesson,.example,.pitfall{background:#f3f2ee!important;-webkit-print-color-adjust:exact;print-color-adjust:exact}pre{white-space:pre-wrap;overflow:visible;font-size:8.2pt;line-height:1.45;background:#f4f4ef!important;color:#18231e!important;border:1px solid #ddd;break-inside:auto;border-radius:3px;padding:10pt}pre code{white-space:pre-wrap;overflow-wrap:anywhere}.question-links{font-size:9pt}.number{font-size:10pt}a{color:inherit;text-decoration:none}#sources{break-before:page}}