/* Supply & Return — a stamped-steel supply register on a galvanised duct: louvres tilting open one by one and cool air streaming out, with copper refrigerant line-set as the accent; Saira Condensed for labels and figures, like the data plate on an air handler. */
:root,[data-theme="hvac-tools"]{
--color-primary:#9aaacb;--color-accent:#b0693a;--color-bg:#e9ebec;--color-bg-alt:#dde0e2;
--color-text:#23272b;--color-text-muted:#555c63;--color-border:#c3c8cd;
--card:#f8f9fa;--steel:#2e3236;--steel-2:#41474d;--air:#9aaacb;--air-pale:#dfe6f2;--air-ink:#3d5277;--copper:#b0693a;--copper-pale:#e7c3a7;
--radius-sm:3px;--radius-md:6px;
--font-display:"Saira Condensed","Arial Narrow","Helvetica Neue",Arial,sans-serif;
--font-base:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
--font-mono:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
--louvres:repeating-linear-gradient(180deg,var(--steel) 0 3px,var(--air) 3px 9px);
--galv:linear-gradient(115deg,#ffffff00 30%,#ffffff55 45%,#ffffff00 60%),linear-gradient(#eef0f1,#e3e6e8)}
*{box-sizing:border-box}
body{margin:0;background:var(--color-bg);color:var(--color-text);font-family:var(--font-base);-webkit-font-smoothing:antialiased}
a{color:var(--air-ink)}
:focus-visible{outline:3px solid var(--copper);outline-offset:3px}
/* nav */
.site-nav{background:var(--card);border-bottom:1px solid var(--color-border);box-shadow:inset 0 -3px 0 var(--air)}
.nav-container{position:relative;height:60px;max-width:1160px;margin:auto;padding:0 20px;display:flex;justify-content:space-between;align-items:center}
.nav-brand{display:flex;align-items:center;gap:12px;text-decoration:none}
.nav-logo{height:34px}
.nav-site-name{font:700 24px/1 var(--font-display);color:var(--steel)}
.nav-links,.footer-links{display:flex;gap:22px;flex-wrap:wrap}
.nav-links a,.footer-links a{text-decoration:none;color:var(--color-text-muted);font:600 17px var(--font-display);letter-spacing:.03em;text-transform:uppercase}
.nav-links a:hover,.footer-links a:hover{color:var(--steel);text-decoration:underline;text-decoration-color:var(--copper);text-decoration-thickness:3px}
/* home */
.sr-home{max-width:1160px;margin:auto;padding:0 20px 90px}
.sr-hero{display:grid;grid-template-columns:minmax(0,1fr) 340px;gap:48px;align-items:center;margin:38px 0 40px;padding:40px 44px;background:var(--galv);border:1px solid var(--color-border);border-radius:var(--radius-md)}
.sr-copy small{font:600 15px var(--font-display);letter-spacing:.12em;text-transform:uppercase;color:var(--copper)}
.sr-copy h1{font:700 clamp(36px,5vw,62px)/1 var(--font-display);margin:10px 0 16px;color:var(--steel);letter-spacing:-.01em}
.sr-copy h1 em{font-style:normal;color:var(--air-ink)}
.sr-copy p{font-size:17px;line-height:1.7;color:var(--color-text-muted);max-width:52ch;margin:0}
.sr-vent{position:relative;padding-bottom:110px}
.sr-grille{position:relative;display:flex;flex-direction:column;gap:6px;padding:16px;background:var(--steel);border-radius:var(--radius-md);box-shadow:0 12px 26px #2e323633;perspective:500px}
.sr-grille::before,.sr-grille::after{content:"";position:absolute;width:8px;height:8px;border-radius:50%;background:var(--copper)}
.sr-grille::before{top:5px;left:5px}.sr-grille::after{right:5px;bottom:5px}
.sr-grille i{display:block;height:16px;background:linear-gradient(#c4ccd8,#8d9ab3);border-radius:2px;transform-origin:50% 0;animation:sr-louvre .5s ease-out both}
@keyframes sr-louvre{from{transform:none}to{transform:rotateX(-48deg)}}
.sr-air{position:absolute;left:10%;right:10%;top:100%;margin-top:-104px;height:100px;display:flex;justify-content:space-around}
.sr-air b{display:block;width:3px;height:100%;border-radius:3px;background:linear-gradient(var(--air),transparent);transform-origin:top;animation:sr-flow 1.1s ease-out both}
@keyframes sr-flow{from{transform:scaleY(0);opacity:0}to{transform:none;opacity:1}}
.sr-rail{display:flex;justify-content:space-between;gap:14px;flex-wrap:wrap;padding-bottom:10px;border-bottom:3px solid var(--steel);font:600 19px var(--font-display);letter-spacing:.04em;text-transform:uppercase;color:var(--color-text-muted)}
.sr-rail b{color:var(--steel)}
.sr-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px;margin-top:24px}
.sr-card{display:flex;flex-direction:column;background:var(--card);border:1px solid var(--color-border);border-radius:var(--radius-md);text-decoration:none;color:inherit;overflow:hidden;transition:transform .16s,box-shadow .16s}
.sr-card::before{content:"";height:12px;background:var(--louvres)}
.sr-card:hover{transform:translateY(-3px);box-shadow:0 14px 26px #2e323626}
.sr-card-body{display:flex;flex-direction:column;flex:1;padding:18px 20px 20px}
.sr-plate{align-self:flex-start;padding:2px 9px;border:1.5px solid var(--copper);border-radius:var(--radius-sm);color:var(--copper);font:600 15px var(--font-display);letter-spacing:.06em}
.sr-card h2{font:700 25px/1.05 var(--font-display);margin:12px 0 8px;color:var(--steel)}
.sr-card p{margin:0 0 16px;font-size:14px;line-height:1.65;color:var(--color-text-muted);flex:1}
.sr-open{font:600 17px var(--font-display);letter-spacing:.06em;text-transform:uppercase;color:var(--air-ink)}
.sr-note{margin-top:34px;padding:16px 18px;border-left:6px solid var(--copper);border-radius:var(--radius-sm);background:var(--card);font-size:14px;line-height:1.7;color:var(--color-text-muted)}
/* detail */
.srd-page{max-width:1080px;margin:auto;padding:24px 20px 90px}
.srd-crumb{font-size:13px;color:var(--color-text-muted)}
.srd-crumb a{text-decoration:none;font-weight:700}
.srd-head{max-width:800px;padding:30px 0 24px}
.srd-kicker{display:inline-block;padding:2px 10px;border:1.5px solid var(--copper);border-radius:var(--radius-sm);color:var(--copper);font:600 15px var(--font-display);letter-spacing:.12em}
.srd-head h1{font:700 clamp(36px,5vw,58px)/1.02 var(--font-display);margin:14px 0 14px;color:var(--steel)}
.srd-head p{font-size:18px;line-height:1.7;color:var(--color-text-muted);margin:0}
.srd-tool{background:var(--card);border:1px solid var(--color-border);border-radius:var(--radius-md);overflow:hidden;margin:14px 0 50px;box-shadow:0 16px 32px #2e32361a}
.srd-tool-label{display:flex;justify-content:space-between;align-items:center;gap:16px;padding:12px 24px;background:var(--steel);color:#eef0f1;font:700 20px var(--font-display);letter-spacing:.03em}
.srd-tool-label i{flex:0 1 130px;height:22px;border-radius:2px;background:var(--louvres)}
.srd-tool-body{padding:28px}
.srd-layout{display:grid;grid-template-columns:minmax(0,1fr) 250px;gap:56px}
.srd-reading{font-size:17px;line-height:1.8}
.srd-reading h2{font:700 30px/1.1 var(--font-display);margin:36px 0 12px;color:var(--steel)}
.srd-reading p{margin:0 0 14px}
.srd-reading ol,.srd-reading ul{margin:0 0 16px;padding-left:22px}
.srd-reading ol{list-style:decimal}.srd-reading ul{list-style:disc}
.srd-reading li{margin-bottom:7px}
.srd-side{align-self:start;background:var(--card);border:1px solid var(--color-border);border-radius:var(--radius-md);padding:0 20px 20px;color:var(--color-text-muted);font-size:14px;line-height:1.65;overflow:hidden}
.srd-side::before{content:"";display:block;height:12px;margin:0 -20px 18px;background:var(--louvres)}
.srd-side strong{display:block;color:var(--steel);font:700 21px var(--font-display);margin-bottom:6px}
.srd-side a{display:inline-block;margin-top:12px;font-weight:700;text-decoration:none;color:var(--air-ink)}
.srd-side a:hover{text-decoration:underline;text-decoration-color:var(--copper);text-decoration-thickness:3px}
.srd-index{margin-top:20px;border-top:1px solid var(--color-border);padding-top:14px}
.srd-index ul{list-style:none;margin:10px 0 0;padding:0}
.srd-index li{padding:6px 0;font-size:13px}
.srd-index a{display:block;margin:0;font-weight:400;color:var(--color-text)}
.srd-index span[aria-current]{font-weight:700;color:var(--steel);background:linear-gradient(transparent 60%,var(--air-pale) 60%)}
.srd-faq,.srd-related{margin-top:56px}
.srd-faq h2,.srd-related h2{font:700 30px var(--font-display);margin:0 0 16px;color:var(--steel)}
.srd-faq details{border-bottom:1px solid var(--color-border);padding:15px 0}
.srd-faq summary{cursor:pointer;font-weight:700}
.srd-faq p{color:var(--color-text-muted);line-height:1.75}
.srd-related-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px}
.srd-related-card{display:block;background:var(--card);padding:18px 20px 20px;border:1px solid var(--color-border);border-top:6px solid var(--copper);border-radius:var(--radius-md);text-decoration:none;color:inherit;transition:transform .16s}
.srd-related-card:hover{transform:translateY(-3px)}
.srd-related-card h3{font:700 21px/1.1 var(--font-display);margin:0 0 8px;color:var(--steel)}
.srd-related-card p{font-size:14px;line-height:1.6;color:var(--color-text-muted);margin:0 0 12px}
.srd-related-card span{font:600 16px var(--font-display);letter-spacing:.06em;text-transform:uppercase;color:var(--air-ink)}
.srd-disclaimer{margin:44px 0 0;padding:16px 18px;border-left:6px solid var(--copper);border-radius:var(--radius-sm);background:var(--card);font-size:14px;line-height:1.7;color:var(--color-text-muted)}
.site-footer{background:var(--card);border-top:1px solid var(--color-border);padding:32px 20px;text-align:center}
.footer-copyright{margin-top:14px;font-size:12px;color:var(--color-text-muted)}
/* tool surface */
[data-theme="hvac-tools"] .tool-row{gap:16px;margin-bottom:18px}
[data-theme="hvac-tools"] .tool-field{font-size:13px;font-weight:700;color:var(--color-text-muted);gap:7px}
[data-theme="hvac-tools"] .tool-input,[data-theme="hvac-tools"] .tool-textarea{border:1.5px solid var(--color-border);border-radius:var(--radius-sm);background:#fff;padding:10px 12px;font:16px/1.4 var(--font-base);color:var(--color-text)}
[data-theme="hvac-tools"] .tool-input:focus{outline:0;border-color:var(--steel);box-shadow:0 0 0 3px #9aaacb99}
[data-theme="hvac-tools"] .tool-btn{border-radius:var(--radius-sm);font:700 17px var(--font-display);letter-spacing:.04em}
[data-theme="hvac-tools"] .tool-btn-primary{background:var(--air);color:var(--steel);border:0}
[data-theme="hvac-tools"] .tool-btn-secondary{background:#fff;border:1.5px solid var(--color-border);color:var(--steel)}
[data-theme="hvac-tools"] .tool-result-box{margin-top:22px;padding:22px;border-radius:var(--radius-sm);background:#fff;border:1px solid var(--color-border);border-left:6px solid var(--air);font-size:15px;word-break:normal}
[data-theme="hvac-tools"] .tool-stat-hero{margin:0 0 8px;font:700 clamp(40px,7vw,60px)/1 var(--font-display);color:var(--steel)}
[data-theme="hvac-tools"] .tool-unit{display:inline-block;margin-left:12px;font:600 20px var(--font-display);color:var(--copper);vertical-align:middle;letter-spacing:.02em}
[data-theme="hvac-tools"] .tool-hint{font-size:14px;line-height:1.7;color:var(--color-text-muted);margin:8px 0 0}
[data-theme="hvac-tools"] .tool-hint strong{color:var(--steel)}
[data-theme="hvac-tools"] .tool-scroll{overflow-x:auto;margin-top:14px}
[data-theme="hvac-tools"] .tool-table td,[data-theme="hvac-tools"] .tool-table th{font-size:14px;background:#fff}
[data-theme="hvac-tools"] .tool-table th{background:var(--steel);color:#eef0f1;font:600 15px var(--font-display);letter-spacing:.04em}
@media(max-width:960px){
.sr-grid,.srd-related-grid{grid-template-columns:repeat(2,1fr)}
.sr-hero{grid-template-columns:minmax(0,1fr) 260px;gap:28px;padding:32px}
}
@media(max-width:768px){
.sr-hero{display:none}
.sr-home{padding:24px 16px 60px}
.sr-grid,.srd-related-grid{grid-template-columns:1fr}
.srd-head{padding-top:22px}
.srd-layout{grid-template-columns:1fr;gap:28px}
.srd-tool-body{padding:20px 16px}
.srd-tool-label{padding:12px 16px}
}
@media(prefers-reduced-motion:reduce){
.sr-grille i,.sr-air b{animation:none}
.sr-grille i{transform:rotateX(-48deg)}
.sr-card:hover,.srd-related-card:hover{transform:none}
}
[data-theme="hvac-tools"] .static-page-container a{color:var(--air-ink)}
[data-theme="hvac-tools"] .guide-breadcrumb a,[data-theme="hvac-tools"] .guide-index-link{color:var(--air-ink)}