:root{--navy:#123e67;--teal:#087e8b;--ink:#182535;--muted:#5a6878;--line:#dce3e9;--soft:#f4f7f9;--white:#fff}*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:86px}body{margin:0;font-family:Inter,"Segoe UI",Arial,sans-serif;color:var(--ink);line-height:1.7;background:#fff}a{color:var(--navy)}a:hover{color:var(--teal)}.topbar{height:76px;position:sticky;top:0;z-index:5;background:#fff;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;padding:0 max(22px,calc((100vw - 1200px)/2));gap:20px}.brand img{display:block;width:190px;max-width:60vw}.topbar nav{display:flex;gap:24px}.topbar nav a,.chapter-nav a{text-decoration:none;font-size:.91rem;font-weight:650}.menu-toggle{display:none;background:#fff;border:1px solid var(--line);border-radius:6px;padding:8px 12px}.hero{max-width:1200px;margin:auto;padding:76px 24px 68px;display:grid;grid-template-columns:1.05fr .95fr;gap:45px;align-items:center}.eyebrow{font-size:.76rem;font-weight:800;letter-spacing:.13em;color:var(--teal);margin:0 0 10px}.hero h1{font-size:clamp(2.7rem,5vw,4.6rem);line-height:1.06;letter-spacing:-.05em;margin:12px 0 22px}.hero h1 span{display:block;color:var(--navy)}.lead{font-size:1.2rem;color:#455568;max-width:650px}.byline{font-size:.92rem;color:var(--muted);margin-top:25px}.hero blockquote{border-left:3px solid var(--teal);padding:10px 18px;margin:22px 0;color:#435469;background:#f6f8fa}.button{display:inline-block;border:0;border-radius:6px;background:var(--navy);color:#fff;text-decoration:none;padding:12px 19px;font:inherit;font-weight:700;cursor:pointer}.button:hover{background:#0b2e4e;color:#fff}.hero-art{min-height:350px;background:#f3f6f8;border:1px solid var(--line);padding:38px 30px;display:flex;flex-direction:column;align-items:center;justify-content:center}.browser{width:100%;max-width:370px;background:#fff;border:1px solid #cbd5de;border-radius:9px;overflow:hidden;box-shadow:0 10px 24px #142b3b0b}.browser-bar{background:#eaf0f4;padding:9px 15px;font-size:.8rem;color:#546274}.browser-lines{padding:26px;display:grid;gap:13px}.browser-lines i,.server i{display:block;height:8px;background:#dbe4ea;border-radius:2px}.browser-lines i:nth-child(2){width:76%}.browser-lines i:nth-child(3){width:55%}.browser-lines b{height:27px;width:92px;background:var(--teal);border-radius:3px}.connection{padding:13px;color:var(--teal);font-weight:750}.server{width:190px;background:#fff;border:1px solid #cbd5de;border-radius:7px;padding:16px;display:grid;gap:8px}.server strong{color:var(--navy)}.server span{font-size:.8rem;color:var(--muted)}.server i:nth-of-type(2){width:65%}.intro{background:var(--soft);border-block:1px solid var(--line);padding:24px max(24px,calc((100vw - 1150px)/2));display:grid;grid-template-columns:repeat(3,1fr);gap:24px}.intro div{display:grid;gap:2px}.intro span{font-size:.91rem;color:var(--muted)}.section{max-width:1160px;padding:66px 24px;margin:auto}.section h2,.chapter h2,.services h2{font-size:clamp(1.9rem,3vw,2.7rem);letter-spacing:-.035em;line-height:1.2;margin:8px 0 14px}.section>p:not(.eyebrow){color:var(--muted)}label[for=chapter-search]{display:block;font-weight:700;margin:24px 0 6px}input[type=search]{width:100%;max-width:480px;padding:12px 14px;border:1px solid #bfcbd5;border-radius:5px;font:inherit}.toc{display:grid;grid-template-columns:repeat(2,1fr);gap:10px;margin-top:20px}.toc>a{display:flex;gap:14px;align-items:flex-start;border:1px solid var(--line);border-radius:7px;padding:16px;color:var(--ink);text-decoration:none}.toc>a:hover{background:var(--soft);border-color:#a7b8c6}.toc>a>b{color:var(--teal);font-size:.82rem}.toc span{display:grid;gap:3px}.toc small{color:var(--muted);font-size:.86rem}.reading-layout{max-width:1200px;margin:auto;padding:0 24px 70px;display:grid;grid-template-columns:210px minmax(0,1fr);gap:46px;align-items:start}.sidebar{position:sticky;top:98px;max-height:calc(100vh - 110px);overflow:auto}.progress-track{height:5px;background:#e6ebef;border-radius:9px;overflow:hidden}.progress-track span{height:100%;display:block;width:0;background:var(--teal)}#progress-text{font-size:.8rem;color:var(--muted)}.chapter-nav{display:grid;gap:7px}.chapter-nav a{color:#435469;font-size:.82rem;padding:4px 0}.chapter{padding:12px 0 43px;border-bottom:1px solid var(--line);margin-bottom:32px;scroll-margin-top:90px}.chapter h3{font-size:1.18rem;margin:24px 0 8px}.chapter p,.chapter li{color:#35465a}.chapter ul,.chapter ol{padding-left:23px}.flow{display:grid;grid-template-columns:repeat(4,1fr);gap:10px;margin:26px 0}.flow>div{border:1px solid var(--line);border-radius:7px;padding:14px 12px;display:flex;flex-direction:column;gap:6px}.flow b{display:grid;place-items:center;width:28px;height:28px;background:var(--navy);color:#fff;border-radius:50%;font-size:.8rem}.flow strong{font-size:.92rem}.flow small{font-size:.79rem;color:var(--muted);line-height:1.5}.note,.analogy{padding:17px 20px;background:#f3f7f8;border-left:3px solid var(--teal);margin:23px 0}.analogy{background:#f7f7f4;border-color:#9b9b82}.analogy p{margin-bottom:0}.table-wrap{overflow-x:auto;border:1px solid var(--line);border-radius:7px;margin:20px 0}.table-wrap table{width:100%;border-collapse:collapse;min-width:620px;font-size:.91rem}.table-wrap th,.table-wrap td{text-align:left;padding:12px 14px;border-bottom:1px solid var(--line);vertical-align:top}.table-wrap th{background:#f1f5f7;color:var(--navy)}.table-wrap tr:last-child td{border-bottom:0}.choice-list{display:grid;gap:12px}.choice-list article{border:1px solid var(--line);border-radius:7px;padding:16px 18px}.choice-list article>b{color:var(--teal);font-size:.78rem;text-transform:uppercase;letter-spacing:.06em}.choice-list h3{margin:3px 0}.choice-list p{margin:0}.glossary{display:grid;grid-template-columns:160px 1fr;gap:12px 20px}.glossary dt{font-weight:750;color:var(--navy)}.glossary dd{margin:0;color:#35465a}.checklist{list-style:none;padding:0!important}.checklist li{position:relative;padding:9px 0 9px 29px;border-bottom:1px solid #edf0f2}.checklist li:before{content:"✓";position:absolute;left:0;color:var(--teal);font-weight:800}.quiz-question{padding:19px 0;border-bottom:1px solid var(--line)}.quiz-question label{display:block;padding:5px 0;color:#35465a;cursor:pointer}.quiz-question input{accent-color:var(--navy);margin-right:8px}.feedback{font-size:.9rem;font-weight:650;margin-bottom:0}.resources{display:grid;grid-template-columns:repeat(2,1fr);gap:10px}.resources a{border:1px solid var(--line);border-radius:6px;padding:13px 15px;text-decoration:none;font-weight:700;display:flex;justify-content:space-between;gap:8px}.resources span{font-size:.8rem;color:var(--teal);white-space:nowrap}.services{background:#f3f6f8;border-top:1px solid var(--line);text-align:center;padding:55px 24px}.services>p:not(.eyebrow){max-width:650px;margin:14px auto;color:#536274}.services h2{max-width:750px;margin:8px auto}footer{border-top:1px solid var(--line);padding:18px 24px;display:flex;justify-content:space-between;gap:12px;max-width:1200px;margin:auto;font-size:.85rem;color:var(--muted)}footer p{margin:0}footer a{text-decoration:none;font-weight:700}@media(max-width:850px){.hero{grid-template-columns:1fr;gap:25px;padding-top:48px}.hero-art{min-height:300px}.reading-layout{grid-template-columns:1fr;gap:0}.sidebar{position:static;max-height:none;margin-bottom:28px}.chapter-nav{grid-template-columns:repeat(3,1fr)}.flow{grid-template-columns:repeat(2,1fr)}.intro{grid-template-columns:1fr;gap:15px}.toc{grid-template-columns:1fr}}@media(max-width:600px){.topbar{height:66px;padding:0 18px}.brand img{width:165px}.menu-toggle{display:block}.topbar nav{display:none;position:absolute;top:65px;left:0;right:0;background:#fff;border-bottom:1px solid var(--line);padding:15px 22px;flex-direction:column;gap:14px}.topbar nav.open{display:flex}.hero{padding:42px 20px}.hero h1{font-size:2.7rem}.hero-art{padding:28px 18px;min-height:270px}.section{padding:48px 20px}.reading-layout{padding:0 20px 48px}.chapter-nav{grid-template-columns:repeat(2,1fr)}.flow{grid-template-columns:1fr 1fr}.glossary{grid-template-columns:1fr;gap:3px}.glossary dd{margin-bottom:13px}.resources{grid-template-columns:1fr}.services{padding:42px 20px}footer{padding:18px 20px;flex-wrap:wrap}}