:root{--ink:#17222d;--muted:#5b6874;--blue:#1261a0;--line:#d8e0e6;--paper:#fbfcfd;--soft:#f3f6f8;font-family:Inter,ui-sans-serif,system-ui,-apple-system,Segoe UI,sans-serif;color:var(--ink);background:var(--paper);line-height:1.65}*{box-sizing:border-box}body{margin:0}.shell{width:min(1160px,calc(100% - 40px));margin-inline:auto}.site-header{border-bottom:1px solid var(--line);background:#fbfcfdf5}.header-inner{min-height:76px;display:flex;align-items:center;justify-content:space-between;gap:32px}.brand{color:var(--ink);text-decoration:none;display:grid;line-height:1.25}.brand span{font-size:.76rem;color:var(--muted);letter-spacing:.08em;text-transform:uppercase}.site-header nav{display:flex;gap:28px}.site-header nav a{color:var(--muted);text-decoration:none;font-size:.92rem}.site-header nav a:hover,.text-link{color:var(--blue)}.hero{padding-block:112px 92px;max-width:1000px;margin-left:max(20px,calc((100% - 1160px)/2))}.eyebrow{color:var(--blue);font-weight:700;font-size:.76rem;letter-spacing:.14em;text-transform:uppercase;margin:0 0 18px}.hero h1{font-family:Georgia,serif;font-size:clamp(2.7rem,6vw,5.6rem);line-height:1.02;letter-spacing:-.045em;margin:0;max-width:980px}.hero h1 span{color:#52616d}.lead{font-size:clamp(1.2rem,2vw,1.55rem);max-width:780px;margin:34px 0 14px}.intro{max-width:720px;color:var(--muted);font-size:1.05rem}.text-link{display:inline-block;margin-top:18px;font-weight:700;text-decoration:none}.section{padding-block:72px;border-top:1px solid var(--line)}.section-heading h2{font-family:Georgia,serif;font-size:clamp(2rem,4vw,3rem);margin:0 0 30px}.featured-note{display:grid;grid-template-columns:1fr auto;align-items:end;gap:40px;padding:38px 0;border-top:2px solid var(--ink);border-bottom:1px solid var(--line)}.featured-note h3{font-size:1.65rem;margin:.35rem 0}.featured-note p{color:var(--muted);max-width:720px}.meta{font-size:.78rem;text-transform:uppercase;letter-spacing:.08em}.button{background:var(--ink);color:#fff;text-decoration:none;padding:11px 18px;font-weight:700;font-size:.9rem;border-radius:2px}footer{border-top:1px solid var(--line);padding:36px 0;color:var(--muted)}footer .shell{display:flex;justify-content:space-between;gap:24px;font-size:.86rem}footer strong{color:var(--ink)}@media(max-width:760px){.header-inner{align-items:flex-start;padding-block:18px}.site-header nav{gap:14px;flex-wrap:wrap;justify-content:flex-end}.hero{padding-block:72px 64px}.featured-note{grid-template-columns:1fr;align-items:start}footer .shell{display:grid}}@media(max-width:520px){.header-inner{display:grid}.site-header nav{justify-content:flex-start}.site-header nav a{font-size:.82rem}.shell{width:min(100% - 28px,1160px)}}html{scroll-behavior:smooth}a{transition:color .15s ease}.site-header{position:relative;z-index:2}.page-header{padding-block:82px 60px;border-bottom:1px solid var(--line)}.page-header h1,.about h1,.article-header h1{font-family:Georgia,serif;letter-spacing:-.035em}.page-header h1{font-size:clamp(2.7rem,6vw,4.7rem);margin:0}.page-header>p:last-child{font-size:1.12rem;color:var(--muted);max-width:680px}.library{padding-block:48px 90px}.filters{display:flex;align-items:end;justify-content:space-between;gap:24px;margin-bottom:36px}.filters label{font-weight:700;font-size:.82rem;display:grid;gap:7px}.filters input{width:min(420px,80vw);padding:12px 14px;border:1px solid var(--line);background:#fff;font:inherit}.filter-buttons{display:flex;gap:8px;flex-wrap:wrap}.filter-buttons button{border:1px solid var(--line);background:transparent;padding:8px 12px;color:var(--muted);cursor:pointer}.filter-buttons button.active{background:var(--ink);color:#fff;border-color:var(--ink)}.notes-grid{display:grid;grid-template-columns:repeat(3,1fr);border-top:2px solid var(--ink)}.note-card{padding:30px;border-bottom:1px solid var(--line);border-right:1px solid var(--line)}.note-card:first-child{padding-left:0}.note-card h2{font-family:Georgia,serif;font-size:1.55rem;line-height:1.2;margin:.5rem 0}.note-card h2 a{color:var(--ink);text-decoration:none}.note-card>p:not(.meta){color:var(--muted)}.card-footer{display:flex;justify-content:space-between;align-items:end;gap:18px;font-size:.78rem;color:var(--muted);margin-top:32px}.card-footer a,.topic-grid a,.home-topics a{color:var(--blue);font-weight:700;text-decoration:none}.home-topics{display:grid;grid-template-columns:1fr 1fr;border-top:2px solid var(--ink)}.home-topics a{display:grid;grid-template-columns:42px 1fr auto;align-items:center;color:var(--ink);padding:19px 6px;border-bottom:1px solid var(--line)}.home-topics a:nth-child(odd){margin-right:32px}.home-topics span{color:var(--blue);font-size:.75rem}.topic-grid{display:grid;grid-template-columns:repeat(2,1fr);padding-block:20px 90px}.topic-grid article{padding:42px;border-bottom:1px solid var(--line)}.topic-grid article:nth-child(odd){padding-left:0;border-right:1px solid var(--line)}.topic-grid article>span{color:var(--blue);font-size:.75rem}.topic-grid h2{font-family:Georgia,serif;margin:.6rem 0;font-size:1.55rem}.topic-grid p{color:var(--muted)}.about{padding-block:110px;display:grid;grid-template-columns:1fr 1fr;gap:90px}.about .eyebrow{grid-column:1/-1}.about h1{font-size:clamp(2.7rem,5vw,4.5rem);line-height:1.05;margin:0}.about div{font-size:1.1rem;color:var(--muted)}.article-header{padding-block:68px 48px;border-bottom:1px solid var(--line)}.back-link{color:var(--muted);text-decoration:none;font-size:.85rem;display:block;margin-bottom:50px}.article-header h1{font-size:clamp(2.7rem,6vw,5rem);line-height:1.05;max-width:980px;margin:0}.article-subtitle{font-size:1.3rem;color:var(--muted);max-width:820px}.article-meta{display:flex;gap:24px;flex-wrap:wrap;font-size:.8rem;color:var(--muted);margin-top:28px}.article-grid{display:grid;grid-template-columns:minmax(0,760px) 240px;gap:100px;justify-content:center;padding-block:66px}.prose{font-family:Georgia,serif;font-size:1.08rem}.prose h2{font-size:2rem;margin:2.8em 0 .6em;scroll-margin-top:30px}.prose h2:first-child{margin-top:0}.prose h3{font-size:1.35rem}.prose p,.prose li{color:#2d3a44}.prose code{font-family:ui-monospace,monospace;background:var(--soft);padding:.15em .3em}.toc{align-self:start;position:sticky;top:30px;border-left:1px solid var(--line);padding-left:22px;font-size:.8rem}.toc ol{list-style:none;padding:0}.toc li{margin:10px 0}.toc a{color:var(--muted);text-decoration:none}.callout{font-family:Inter,sans-serif;margin:34px 0;padding:22px 24px;border-left:3px solid var(--blue);background:#f1f6fa}.callout.warning{border-color:#9b5b14;background:#fbf6ee}.callout.calculation-result{border-color:#27775a;background:#eef8f4}.callout>strong{text-transform:uppercase;letter-spacing:.08em;font-size:.72rem}.callout p{margin:.5em 0 0}.engineering-figure{margin:42px 0}.engineering-figure.medium{max-width:600px}.figure-placeholder{min-height:310px;border:1px solid #aebbc5;background:repeating-linear-gradient(135deg,#f7f9fa,#f7f9fa 10px,#f1f4f6 10px 11px);display:grid;place-content:center;text-align:center;font-family:Inter,sans-serif;color:var(--muted)}.figure-placeholder span{font-size:.68rem;letter-spacing:.14em;color:var(--blue)}.figure-placeholder strong{margin-top:8px}.figure-placeholder small{margin-top:4px}.engineering-figure figcaption,.engineering-table figcaption{font-family:Inter,sans-serif;font-size:.78rem;color:var(--muted);margin-top:10px}.table-scroll{overflow-x:auto}.engineering-table{margin:40px 0}.engineering-table table{border-collapse:collapse;width:100%;font-family:Inter,sans-serif;font-size:.86rem}.engineering-table th,.engineering-table td{text-align:left;padding:12px 14px;border:1px solid var(--line)}.engineering-table th{background:var(--soft)}.equation-block{position:relative;overflow-x:auto;padding:25px;background:#fff;border-block:1px solid var(--line);margin:34px 0;text-align:center}.equation-label{position:absolute;right:14px;top:50%;transform:translateY(-50%);font-family:Inter,sans-serif;font-size:.8rem}.references{border-top:2px solid var(--ink);margin-top:60px}.references li{font-size:.92rem;margin:10px 0}.article-nav{border-top:1px solid var(--line);padding-block:30px 70px;display:flex;justify-content:space-between;font-size:.85rem}.article-nav a{color:var(--blue);text-decoration:none}.article-nav span{color:var(--muted)}@media(max-width:900px){.notes-grid{grid-template-columns:1fr 1fr}.article-grid{grid-template-columns:minmax(0,760px)}.toc{display:none}.about{gap:50px}.filters{align-items:start;flex-direction:column}}@media(max-width:650px){.notes-grid,.topic-grid,.home-topics,.about{grid-template-columns:1fr}.note-card,.note-card:first-child{padding:26px 0;border-right:0}.topic-grid article,.topic-grid article:nth-child(odd){padding:30px 0;border-right:0}.home-topics a:nth-child(odd){margin-right:0}.about{gap:22px;padding-block:75px}.about .eyebrow{grid-column:auto}.article-grid{padding-block:44px}.article-header{padding-block:48px 32px}.article-header--compact-mobile-title h1{font-size:clamp(2.15rem,9vw,2.35rem)}.card-footer{align-items:start;flex-direction:column}.article-nav{align-items:start;flex-direction:column;gap:12px}}.hero h1{font-size:clamp(3.2rem,6vw,5.2rem)}.footer-links{display:flex;gap:8px;align-items:center}.footer-links a{color:inherit}.policy{max-width:800px;padding-block:52px 90px}.policy h2,.settings-notes h2{font-family:Georgia,serif;font-size:1.55rem;margin:2em 0 .45em}.policy p{color:#2d3a44}.policy a{color:var(--blue)}.policy-updated{font-size:.8rem;color:var(--muted)!important;text-transform:uppercase;letter-spacing:.08em}.analytics-settings{max-width:800px;padding-block:52px 90px}.analytics-status{border-top:2px solid var(--ink);border-bottom:1px solid var(--line);padding:30px 0}.analytics-status>span{display:block;color:var(--blue);font-size:.75rem;font-weight:700;text-transform:uppercase;letter-spacing:.1em}.analytics-status strong{display:block;font-family:Georgia,serif;font-size:1.8rem;margin-top:6px}.analytics-status p{color:var(--muted);margin:.35rem 0 0}.analytics-actions{display:flex;gap:12px;flex-wrap:wrap;padding-block:28px}.analytics-actions button{border:1px solid var(--ink);background:var(--ink);color:#fff;padding:11px 17px;font:inherit;font-weight:700;cursor:pointer}.analytics-actions button.secondary{background:transparent;color:var(--ink)}.analytics-actions button:disabled{opacity:.45;cursor:not-allowed}.settings-notes{background:var(--soft);border-left:3px solid var(--blue);padding:18px 26px}.settings-notes h2{font-size:1.2rem;margin:.3rem 0}.settings-notes li{margin:.45rem 0;color:var(--muted)}@media(max-width:760px){footer .shell{gap:14px}.footer-links{flex-wrap:wrap}.privacy-header{padding-block:58px 42px}}.article-cover{margin-block:48px 0;max-width:860px}.article-cover img,.engineering-figure img{display:block;width:100%;height:auto;background:#fff}.article-cover figcaption{font-size:.78rem;color:var(--muted);margin-top:10px;line-height:1.5}.contact-options{padding-block:52px 90px}.contact-option{display:grid;grid-template-columns:minmax(220px,.7fr) minmax(300px,1.3fr) auto;align-items:start;gap:32px;padding:30px 0;border-bottom:1px solid var(--line)}.contact-option:first-child{border-top:2px solid var(--ink)}.contact-option h2{font-family:Georgia,serif;font-size:1.55rem;line-height:1.25;margin:0}.contact-option p{color:var(--muted);margin:0}.contact-option a{color:var(--blue);font-weight:700;text-decoration:none;white-space:nowrap}.contact-option a:hover{text-decoration:underline}@media(max-width:760px){.contact-header{padding-block:58px 42px}.contact-options{padding-block:40px 70px}.contact-option{grid-template-columns:1fr;gap:10px;padding:26px 0}.contact-option p{max-width:600px}}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}.portal-shell{display:grid;grid-template-columns:272px minmax(0,1fr);min-height:100vh}.portal-content{min-width:0;display:flex;flex-direction:column}.portal-content>main{flex:1}.portal-sidebar{position:sticky;top:0;height:100vh;overflow-y:auto;display:flex;flex-direction:column;padding:34px 25px 28px;background:linear-gradient(180deg,#122b43,#0c2237);color:#fff}.portal-brand,.mobile-brand{display:grid;line-height:1.15;text-decoration:none}.portal-brand{color:#fff;padding:0 10px 30px;border-bottom:1px solid rgba(255,255,255,.13)}.portal-brand strong,.mobile-brand strong{font-size:1.15rem;letter-spacing:.055em}.portal-brand span,.mobile-brand span{font-size:.64rem;letter-spacing:.15em;opacity:.62;margin-top:5px}.portal-navigation{padding-top:23px}.portal-navigation a,.portal-navigation .nav-future{display:block;text-decoration:none}.portal-home-link{display:flex!important;align-items:center;gap:10px;padding:9px 10px;margin-bottom:20px;color:#e8f3fb;font-weight:700;font-size:.92rem;border-radius:5px}.nav-home-icon{font-size:1rem;color:#83bee9}.portal-navigation a:hover,.portal-navigation a.active{color:#fff;background:#74b8e821}.portal-nav-section{margin:0 0 21px}.portal-nav-section h2{margin:0 10px 7px;color:#7fb9e4;font-size:.65rem;letter-spacing:.14em;text-transform:uppercase}.portal-nav-section>div{display:grid;gap:2px}.portal-nav-section a,.portal-nav-section .nav-future{padding:6px 10px;color:#c6d4df;font-size:.79rem;line-height:1.35;border-radius:4px}.portal-nav-section .nav-future{color:#879aaa;cursor:default}.sidebar-statement{margin:auto 0 0;padding:22px 10px 0;border-top:1px solid rgba(255,255,255,.13)}.sidebar-statement p{margin:0;color:#aebfcb;font-family:Georgia,serif;font-size:.78rem;line-height:1.55}.sidebar-statement cite{display:block;margin-top:8px;color:#6faedb;font-style:normal;font-size:.65rem;letter-spacing:.08em}.content-topbar{min-height:72px;display:flex;align-items:center;padding:12px clamp(20px,4vw,54px);border-bottom:1px solid var(--line);background:#fbfcfdf2}.portal-search{width:min(560px,100%);position:relative;display:block}.portal-search input{width:100%;height:42px;padding:0 16px 0 43px;border:1px solid #d2dde5;border-radius:7px;background:#fff;color:var(--ink);font:inherit;font-size:.88rem;outline:none}.portal-search input::placeholder{color:#82909c}.search-icon{position:absolute;left:16px;top:50%;width:14px;height:14px;border:1.8px solid #6f8291;border-radius:50%;transform:translateY(-58%)}.search-icon:after{content:"";position:absolute;width:6px;height:1.8px;background:#6f8291;right:-5px;bottom:-2px;transform:rotate(45deg)}.mobile-header{display:none}.portal-footer{margin-top:auto;padding:31px 0;border-top:1px solid var(--line);color:var(--muted);background:#fff}.portal-footer .shell{display:grid;grid-template-columns:minmax(220px,1fr) auto auto;align-items:center;gap:30px;font-size:.78rem}.footer-branding{display:grid;gap:3px}.footer-branding strong{color:var(--ink);letter-spacing:.05em}.footer-navigation{display:flex;gap:18px;flex-wrap:wrap}.footer-navigation a{color:var(--muted);text-decoration:none}.footer-navigation a:hover{color:var(--blue)}.footer-copyright{white-space:nowrap}.portal-home{padding-block:42px 72px}.home-hero{position:relative;isolation:isolate;min-height:610px;overflow:hidden;display:flex;flex-direction:column;justify-content:space-between;padding:clamp(52px,7vw,94px) clamp(34px,7vw,94px) 40px;border:1px solid #d8e7f2;border-radius:12px;background:linear-gradient(125deg,#fff,#f3f9fd 58%,#e5f3fb)}.home-hero:before,.home-hero:after{content:"";position:absolute;z-index:-1;border-radius:50%;filter:blur(2px);pointer-events:none}.home-hero:before{width:660px;height:330px;right:-260px;top:-70px;border:1px solid rgba(55,139,198,.14);box-shadow:0 0 0 62px #7ec1e70b,0 0 0 124px #7ec1e709}.home-hero:after{width:520px;height:250px;right:-180px;bottom:-180px;background:#5ca8d812;box-shadow:-90px -25px #ffffff7a}.hero-content{max-width:850px}.home-hero .eyebrow{margin-bottom:24px}.home-hero h1{max-width:820px;margin:0;font-family:Georgia,serif;font-size:clamp(3rem,5.5vw,5.25rem);line-height:1.02;letter-spacing:-.047em;color:#142c42}.home-hero-intro{max-width:700px;margin:28px 0 0;color:#536979;font-size:1.08rem;line-height:1.75}.hero-button{display:inline-flex;align-items:center;gap:18px;margin-top:34px;padding:13px 19px;background:#133b5d;color:#fff;border-radius:4px;text-decoration:none;font-weight:700;font-size:.9rem}.hero-button:hover{background:#0c2e49}.hero-values{display:flex;gap:clamp(22px,4vw,52px);flex-wrap:wrap;margin-top:60px;padding-top:25px;border-top:1px solid rgba(64,112,146,.18);color:#496274;font-size:.8rem;font-weight:700}.hero-values span{display:flex;align-items:center;gap:8px}.hero-values b{width:21px;height:21px;display:grid;place-items:center;border:1px solid #a6cce5;border-radius:50%;color:#1870aa;font-size:.68rem;background:#ffffffb3}@media(max-width:980px){.portal-shell{display:block}.portal-sidebar{display:none}.mobile-header{position:sticky;top:0;z-index:10;min-height:68px;display:flex;align-items:center;justify-content:space-between;padding:12px 20px;border-bottom:1px solid var(--line);background:#fbfcfdfa}.mobile-brand{color:var(--ink)}.mobile-menu summary{display:flex;align-items:center;gap:10px;padding:8px 3px;list-style:none;cursor:pointer;color:var(--ink);font-size:.8rem;font-weight:700}.mobile-menu summary::-webkit-details-marker{display:none}.menu-icon,.menu-icon:before,.menu-icon:after{display:block;width:19px;height:1.5px;background:var(--ink)}.menu-icon{position:relative}.menu-icon:before,.menu-icon:after{content:"";position:absolute;left:0}.menu-icon:before{top:-6px}.menu-icon:after{top:6px}.mobile-menu-panel{position:absolute;left:0;right:0;top:100%;max-height:calc(100vh - 68px);overflow-y:auto;padding:8px 20px 24px;background:#10283e;border-top:1px solid rgba(255,255,255,.1);box-shadow:0 12px 22px #0e23352e}.mobile-menu-panel .portal-navigation{max-width:700px;margin-inline:auto;padding-top:12px}.content-topbar{min-height:64px;padding-inline:20px}.portal-footer .shell{grid-template-columns:1fr auto}.footer-branding{grid-column:1/-1}}@media(max-width:650px){.content-topbar{padding-inline:14px}.portal-home{padding-block:20px 46px}.home-hero{min-height:590px;padding:48px 24px 28px;border-radius:8px}.home-hero h1{font-size:clamp(2.55rem,12vw,3.55rem)}.home-hero-intro{font-size:1rem;line-height:1.65}.hero-button{width:100%;justify-content:space-between}.hero-values{display:grid;gap:13px;margin-top:44px}.portal-footer .shell{grid-template-columns:1fr;gap:18px}.footer-navigation{gap:11px 17px}.footer-copyright{white-space:normal}}@media(min-width:981px){.portal-sidebar{background:linear-gradient(180deg,#f8fbfd,#f1f7fb);color:var(--ink);border-right:1px solid #d7e3eb}.portal-brand{color:#17324a;border-bottom-color:#d7e3eb}.portal-brand span{color:#607688;opacity:1}.portal-home-link{color:#29465d}.nav-home-icon{color:#2c74a6}.portal-navigation a:hover,.portal-navigation a.active{color:#143652;background:#deedf7}.portal-nav-section h2{color:#3274a1}.portal-nav-section a{color:#425b6d}.portal-nav-section .nav-future{color:#8a9aa6}.sidebar-statement{border-top-color:#d7e3eb}.sidebar-statement p{color:#536b7d}.sidebar-statement cite{color:#2f76a8}}.portal-home{padding-block:34px 56px}.home-hero{min-height:510px;padding:clamp(46px,5vw,68px) clamp(34px,6vw,78px) 32px}.home-hero .eyebrow{margin-bottom:19px}.home-hero h1{max-width:850px;font-size:clamp(3.25rem,4.4vw,4rem);line-height:.98;letter-spacing:-.04em}.home-hero-intro{margin-top:22px;line-height:1.65}.hero-button{margin-top:27px}.hero-values{margin-top:42px;padding-top:21px}.contact-header h1{font-size:clamp(2.4rem,4vw,3.5rem);line-height:1.04}@media(max-width:650px){.portal-home{padding-block:18px 42px}.home-hero{min-height:520px;padding:38px 24px 24px}.home-hero .eyebrow{margin-bottom:17px}.home-hero h1{font-size:clamp(2.35rem,10.5vw,3rem);line-height:1}.home-hero-intro{margin-top:20px}.hero-button{margin-top:25px}.hero-values{margin-top:34px;padding-top:19px}.contact-header h1{font-size:2.4rem}}.content-topbar{position:relative;z-index:8}.site-search{position:relative;width:min(560px,100%)}.site-search .portal-search{width:100%}.portal-search input:focus{border-color:#73a9cf;box-shadow:0 0 0 3px #357eb21f}.search-results{position:absolute;top:calc(100% + 7px);left:0;width:100%;max-height:min(480px,calc(100vh - 110px));overflow-y:auto;border:1px solid #cbd9e3;border-radius:7px;background:#fff;box-shadow:0 12px 28px #18304324}.search-results ul{list-style:none;margin:0;padding:5px}.search-results li{margin:0}.search-results a{display:grid;gap:4px;padding:11px 12px;border-radius:4px;color:var(--ink);text-decoration:none}.search-results li+li{border-top:1px solid #edf1f4}.search-results li.active a,.search-results a:hover,.search-results a:focus{background:#edf6fb;outline:none}.search-result-heading{display:flex;align-items:baseline;justify-content:space-between;gap:16px}.search-result-heading strong{font-size:.88rem;line-height:1.35}.search-result-category{flex:0 0 auto;color:#2c70a1;font-size:.66rem;font-weight:700;letter-spacing:.06em;text-transform:uppercase}.search-result-description{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:2;color:var(--muted);font-size:.76rem;line-height:1.45}.search-empty{margin:0;padding:17px;color:var(--muted);font-size:.82rem}@media(max-width:650px){.site-search{width:100%}.search-results{max-height:min(420px,calc(100vh - 150px))}.search-result-heading{align-items:flex-start}.search-result-category{margin-top:2px}.search-results a{padding:10px}.search-result-description{-webkit-line-clamp:2}}