:root{--ink:#17333e;--muted:#58707a;--accent:#175968;--paper:#f4f7f6;--line:#cedbdc;--gold:#eed9a8}*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:24px}body{margin:0;background:var(--paper);color:var(--ink);font:16px/1.85 -apple-system,BlinkMacSystemFont,"PingFang SC","Microsoft YaHei",sans-serif}a{color:inherit;text-underline-offset:.25em}a:hover{color:#a34c22}a:focus-visible{outline:3px solid #a34c22;outline-offset:5px}h1,h2,h3,p,figure{margin:0}h1,h2,h3{line-height:1.35}h1{font-size:clamp(34px,4.2vw,58px);font-weight:650;letter-spacing:-.04em}h2{font-size:clamp(25px,2.6vw,36px);letter-spacing:-.035em}h3{font-size:20px}p+p{margin-top:16px}.site-head,.site-foot,.home-main,.inside-main,.crumb{max-width:1248px;margin:auto}.site-head{display:flex;justify-content:space-between;align-items:center;padding:25px 40px}.brand{font-size:22px;font-weight:700;text-decoration:none;letter-spacing:-.02em}.brand span{display:block;font-size:11px;letter-spacing:.18em;font-weight:500;text-transform:uppercase;color:var(--muted)}.site-head nav{display:flex;gap:30px;font-size:14px}.site-head nav a{text-decoration:none}.skip-link{position:absolute;top:-100px;left:20px;z-index:20;background:white;padding:12px}.skip-link:focus{top:5px}.home-main{padding:0 40px}.hero{position:relative;min-height:560px;display:flex;align-items:center;margin-top:9px;isolation:isolate}.hero figure{position:absolute;inset:0;z-index:-1}.hero img{height:100%;width:100%;object-fit:cover;object-position:68% center;display:block}.hero figcaption{position:absolute;bottom:10px;right:15px;font-size:10px;background:#ffffffde;padding:1px 8px;color:#344952}.hero-note{width:430px;background:#ffffffed;margin:42px;padding:35px 36px;border-top:5px solid var(--accent);box-shadow:0 12px 35px #102a3a12}.eyebrow{display:block;font-size:11px;font-weight:700;letter-spacing:.1em;color:var(--accent);margin-bottom:15px}.hero h1 span{display:block;font-size:.44em;letter-spacing:.02em;font-weight:500;margin-top:5px}.hero h2{font-size:25px;margin:20px 0 12px}.hero p{font-size:15px;color:var(--muted);line-height:1.75}.button{display:inline-block;background:var(--accent);color:white;text-decoration:none;font-size:14px;font-weight:600;padding:11px 20px;margin-top:23px}.button:hover{background:#103d48;color:white}.secondary{font-size:13px;display:inline-block;margin:14px 0 0 16px}.chapter{padding:75px 0;border-bottom:1px solid var(--line)}.chapter-heading{display:grid;grid-template-columns:100px 1fr;gap:15px;margin-bottom:32px}.chapter-number{font-size:14px;color:var(--muted);font-family:ui-monospace,monospace;letter-spacing:.07em;padding-top:7px}.chapter-heading p{color:var(--muted);max-width:640px;margin-top:12px}.address-example{margin-left:115px;padding:30px;background:#e5efee;border-left:4px solid var(--accent)}.address-example code{font-size:clamp(19px,2.5vw,30px);overflow-wrap:anywhere}.address-example strong{background:var(--gold);padding:2px 4px}.address-key{display:flex;gap:40px;margin-top:22px;font-size:13px}.address-key p{margin:0}.address-key b{display:block}.address-example .note{font-size:12px;color:var(--muted);margin-top:18px}.context-link{display:inline-block;margin-top:22px;font-weight:600;font-size:14px}.problem-table{width:100%;border-collapse:collapse;font-size:15px}.problem-table th{text-align:left;background:var(--accent);color:white;font-size:13px;padding:15px 22px;font-weight:500}.problem-table td{padding:24px 22px;border-bottom:1px solid var(--line);vertical-align:top}.problem-table td:first-child{font-weight:600;width:28%}.problem-table td:last-child{color:var(--muted);width:44%}.guide-directory{display:block}.guide-item{display:grid;grid-template-columns:70px 1fr 85px;gap:22px;padding:30px 12px;text-decoration:none;border-top:1px solid var(--line);align-items:center}.guide-item:last-child{border-bottom:1px solid var(--line)}.guide-number{font:14px/1.5 sans-serif;color:var(--muted)}.guide-item p{font-size:14px;color:var(--muted);margin-top:9px}.guide-item:hover{background:#e7efed}.read-label{font-size:12px}.site-foot{padding:48px 40px;display:grid;grid-template-columns:1fr auto;gap:25px}.site-foot p{color:var(--muted);font-size:13px;margin-top:10px}.site-foot>a{font-size:13px}.site-foot small{grid-column:1/-1;font-size:11px;color:var(--muted)}.crumb{font-size:12px;padding:10px 40px 28px;color:var(--muted);overflow-wrap:anywhere}.inside-main{padding:25px 40px 70px;max-width:1000px}.page-intro{max-width:780px;margin-bottom:38px}.page-intro h1{font-size:42px}.page-intro p{font-size:18px;color:var(--muted);margin-top:24px}.sheet-section{padding:28px 0;border-top:1px solid var(--line)}.sheet-section h2{font-size:25px;margin-bottom:16px}.sheet-section p{max-width:760px}.paper-main{max-width:920px;margin:auto;padding:25px 40px 72px}.reading-sheet>header{padding-bottom:32px;border-bottom:1px solid var(--line)}.reading-sheet h1{font-size:clamp(29px,3.6vw,46px)}.article-date{color:var(--muted);font-size:12px;margin-top:24px}.paper-body{max-width:720px;margin:35px auto 0}.paper-body h2{font-size:26px;margin:36px 0 17px}.paper-body p{line-height:1.95}.plain-answer{border-left:4px solid var(--accent);padding:16px 22px;background:#e6efec;font-size:18px}.paper-body ul{padding-left:24px}.paper-body li{margin:9px 0}.inside-main .address-example{margin:0}.history-note{background:#e7edea;padding:23px;border-left:4px solid #617670}.history-note+p{margin-top:25px}.relation{border-top:1px solid var(--line);padding-top:24px;margin-top:32px;font-size:14px}@media(max-width:650px){.site-head{padding:20px;display:block}.brand{font-size:20px}.site-head nav{gap:25px;margin-top:18px;font-size:13px}.home-main{padding:0 20px}.hero{display:flex;flex-direction:column;min-height:0;margin:2px -20px 0;align-items:stretch}.hero figure{position:relative;inset:auto;order:2;height:240px;margin:0 20px}.hero-note{width:auto;margin:0;padding:24px 20px 28px;border-top:1px solid var(--line);box-shadow:none;background:var(--paper)}.hero h1{font-size:39px}.hero h2{font-size:25px;margin:17px 0 10px}.hero p{max-width:340px}.button{margin-top:19px}.secondary{margin-left:15px}.hero img{object-position:65% center}.hero figcaption{font-size:9px;right:8px;bottom:7px}.eyebrow{margin-bottom:10px;font-size:10px}.chapter{padding:44px 0}.chapter-heading{grid-template-columns:35px 1fr;gap:9px;margin-bottom:25px}.chapter-number{font-size:11px;padding-top:5px}.chapter-heading h2{font-size:26px}.chapter-heading p{font-size:14px}.address-example{margin-left:0;padding:23px 18px}.address-key{gap:18px;flex-wrap:wrap}.address-key p{font-size:12px}.problem-table{font-size:13px}.problem-table th{padding:12px 8px;font-size:11px}.problem-table td{padding:18px 8px;line-height:1.75}.problem-table td:first-child{width:27%}.problem-table td:last-child{width:43%}.guide-item{grid-template-columns:26px 1fr;gap:13px;padding:24px 0}.guide-item h3{font-size:18px}.guide-number{font-size:12px;align-self:start;padding-top:4px}.read-label{grid-column:2}.guide-item p{font-size:13px}.site-foot{padding:36px 20px;grid-template-columns:1fr;gap:20px}.site-foot small{grid-column:1}.crumb{padding:8px 20px 20px;font-size:11px}.inside-main,.paper-main{padding:15px 20px 45px}.page-intro h1{font-size:32px}.page-intro p{font-size:16px}.sheet-section h2,.paper-body h2{font-size:23px}.paper-body{margin-top:26px}.paper-body p{font-size:16px}.plain-answer{padding:15px;font-size:16px}.reading-sheet h1{font-size:31px}.article-date{margin-top:20px}}@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}}