/* Boiler Answers - site stylesheet. System fonts, no external requests. */
:root {
  --bg: #fbf9f6;
  --bg-alt: #f3efe8;
  --surface: #ffffff;
  --ink: #1d2733;
  --ink-soft: #4a5a6e;
  --ink-faint: #7b8794;
  --line: #e3dfd7;
  --brand: #1f3a5f;
  --brand-dark: #16294a;
  --accent: #e8893a;
  --accent-dark: #c86f22;
  --green: #2f7d4a;
  --green-bg: #eaf5ec;
  --amber: #b8730a;
  --amber-bg: #fdf3e1;
  --red: #b3261e;
  --red-bg: #fbeae9;
  --blue-bg: #e9f0f8;
  --radius: 12px;
  --shadow: 0 1px 2px rgba(29,39,51,.06), 0 6px 20px -8px rgba(29,39,51,.12);
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  --wrap: 1120px;
  --narrow: 760px;
}
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth;scroll-padding-top:4.5rem}
body{margin:0;font-family:var(--font);font-size:1.0625rem;line-height:1.65;color:var(--ink);background:var(--bg)}
img,svg,video{max-width:100%;height:auto;display:block}
a{color:var(--brand);text-decoration-thickness:1px;text-underline-offset:2px}
a:hover{color:var(--accent-dark)}
h1,h2,h3,h4{line-height:1.25;color:var(--brand-dark);margin:0 0 .6em;font-weight:700;letter-spacing:-.01em}
h1{font-size:clamp(1.8rem,1.3rem + 2.2vw,2.6rem)}
h2{font-size:clamp(1.35rem,1.1rem + 1vw,1.75rem);margin-top:2em}
h3{font-size:1.15rem;margin-top:1.6em}
p,ul,ol{margin:0 0 1.1em}
ul,ol{padding-left:1.4em}
li{margin-bottom:.35em}
code{font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;font-size:.92em;background:var(--bg-alt);padding:.1em .35em;border-radius:4px}
strong{color:var(--brand-dark)}
.wrap{max-width:var(--wrap);margin:0 auto;padding:0 1rem}
.wrap.narrow{max-width:var(--narrow)}
.skip{position:absolute;left:-999px;top:0;background:var(--brand);color:#fff;padding:.5rem 1rem;z-index:100}
.skip:focus{left:1rem;top:1rem}
.lead{font-size:1.15rem;color:var(--ink-soft)}
.btn{display:inline-block;background:var(--brand);color:#fff;font-weight:600;padding:.75rem 1.3rem;border-radius:999px;text-decoration:none;border:0;cursor:pointer;line-height:1.2}
.btn:hover{background:var(--brand-dark);color:#fff}
.btn-cta{background:var(--accent);color:#fff;font-size:1.05rem;padding:.9rem 1.6rem}
.btn-cta:hover{background:var(--accent-dark)}

/* Header */
.site-header{background:var(--surface);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:50}
.site-header .wrap{display:flex;align-items:center;justify-content:space-between;min-height:62px;flex-wrap:wrap;gap:.5rem}
.brand{display:flex;align-items:center;gap:.55rem;text-decoration:none;color:var(--brand-dark)}
.brand-name{font-weight:800;font-size:1.25rem;letter-spacing:-.02em}
.brand-name span{color:var(--accent)}
.site-nav ul{list-style:none;margin:0;padding:0;display:flex;gap:.1rem;flex-wrap:wrap}
.site-nav a{display:block;padding:.55rem .7rem;text-decoration:none;font-weight:600;font-size:.95rem;color:var(--ink-soft);border-radius:8px}
.site-nav a:hover,.site-nav a[aria-current]{color:var(--brand-dark);background:var(--bg-alt)}
.nav-toggle{position:absolute;opacity:0;pointer-events:none}
.nav-burger{display:none;width:44px;height:44px;flex-direction:column;justify-content:center;gap:5px;cursor:pointer;padding:10px;border-radius:8px}
.nav-burger span{display:block;height:2px;background:var(--brand-dark);border-radius:2px}
@media (max-width: 860px){
  .nav-burger{display:flex}
  .site-nav{display:none;width:100%;padding-bottom:.5rem}
  .nav-toggle:checked ~ .site-nav{display:block}
  .site-nav ul{flex-direction:column}
  .site-nav a{padding:.7rem .75rem;font-size:1.05rem}
}

/* Home */
.hero-home{background:linear-gradient(160deg,var(--brand) 0%,#2b4f7e 100%);color:#fff;padding:3.5rem 0 3rem}
.hero-home h1{color:#fff;max-width:18ch}
.hero-home .lead{color:#dfe7f2;max-width:62ch}
.hero-note{font-size:.95rem;color:#c9d6e6;margin:0}
.hero-note a{color:#fff;font-weight:700}
.section{padding:3rem 0}
.section-alt{background:var(--bg-alt)}
.section-title{margin-top:0;font-size:1.5rem}
.hub-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:1rem}
.hub-card{display:flex;flex-direction:column;gap:.3rem;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:1.1rem 1.2rem;text-decoration:none;color:var(--ink);box-shadow:var(--shadow);transition:transform .15s,border-color .15s}
.hub-card:hover{transform:translateY(-2px);border-color:var(--brand);color:var(--ink)}
.hub-code{display:inline-grid;place-items:center;width:34px;height:34px;border-radius:9px;background:var(--brand);color:#fff;font-weight:800;font-size:.95rem}
.hub-name{font-weight:700;color:var(--brand-dark);font-size:1.05rem;margin-top:.3rem}
.hub-desc{font-size:.92rem;color:var(--ink-soft)}
.hub-count{font-size:.8rem;color:var(--ink-faint);margin-top:auto;padding-top:.4rem}
.card-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:1rem}
.card{display:flex;flex-direction:column;gap:.35rem;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:1.1rem 1.2rem;text-decoration:none;color:var(--ink);box-shadow:var(--shadow)}
.card:hover{border-color:var(--brand);color:var(--ink)}
.card-kicker{font-size:.78rem;text-transform:uppercase;letter-spacing:.06em;color:var(--accent-dark);font-weight:700}
.card-title{font-weight:700;color:var(--brand-dark);font-size:1.08rem;line-height:1.3}
.card-desc{font-size:.93rem;color:var(--ink-soft)}
.card-meta{font-size:.8rem;color:var(--ink-faint);margin-top:auto;padding-top:.3rem}
.card-compact .card-title{font-size:1rem}
.how-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:1.5rem}
.how-grid h3{margin-top:0;font-size:1.05rem}
.how-grid p{font-size:.95rem;color:var(--ink-soft)}

/* Article */
.article-header{padding:1.5rem 0 0}
.hub-kicker{text-transform:uppercase;letter-spacing:.08em;font-size:.8rem;font-weight:700;color:var(--accent-dark);margin:0 0 .4rem}
.breadcrumbs ol{list-style:none;padding:0;margin:0 0 1rem;display:flex;flex-wrap:wrap;gap:.3rem;font-size:.85rem;color:var(--ink-faint)}
.breadcrumbs li+li::before{content:"/";margin-right:.3rem;color:var(--line)}
.breadcrumbs a{color:var(--ink-soft);text-decoration:none}
.breadcrumbs a:hover{text-decoration:underline}
.article-meta{display:flex;flex-wrap:wrap;gap:.4rem 1.2rem;font-size:.9rem;color:var(--ink-soft);margin:0 0 1rem}
.article-meta a{color:var(--ink-soft)}
.disclosure{font-size:.85rem;color:var(--ink-soft);background:var(--bg-alt);border-left:3px solid var(--accent);padding:.6rem .9rem;border-radius:0 8px 8px 0;margin:0 0 1.2rem}
.hero-figure{margin:0 0 1.5rem}
.hero-figure img,.hero-figure .img-placeholder{width:100%;aspect-ratio:16/9;object-fit:cover;border-radius:var(--radius);box-shadow:var(--shadow)}
.img-placeholder{height:auto}
figcaption{font-size:.8rem;color:var(--ink-faint);margin-top:.4rem;text-align:right}
.figure{margin:1.8rem 0}
.figure img,.figure .img-placeholder{border-radius:var(--radius);width:100%;aspect-ratio:16/9;object-fit:cover}
.article-body{padding-bottom:2rem}
.article-body h2{padding-top:.2em;border-top:1px solid var(--line);padding-top:1.2em}
.article-body h2:first-child{border-top:0;margin-top:0;padding-top:0}
.article-body li+li{margin-top:.2em}
.table-wrap{overflow-x:auto;margin:1.4rem 0;border:1px solid var(--line);border-radius:10px;background:var(--surface)}
table{border-collapse:collapse;width:100%;font-size:.95rem;min-width:480px}
th,td{padding:.65rem .8rem;text-align:left;vertical-align:top;border-bottom:1px solid var(--line)}
th{background:var(--bg-alt);color:var(--brand-dark);font-weight:700;white-space:nowrap}
tr:last-child td{border-bottom:0}
tbody tr:nth-child(even) td{background:#fcfbf9}
blockquote{margin:1.4rem 0;padding:.6rem 1.2rem;border-left:4px solid var(--brand);background:var(--surface);color:var(--ink-soft);border-radius:0 10px 10px 0}

/* Boxes */
.box{border-radius:var(--radius);padding:1.1rem 1.3rem;margin:1.6rem 0;border:1px solid var(--line);background:var(--surface)}
.box-title{font-weight:800;margin:0 0 .5rem;font-size:1rem;letter-spacing:.01em}
.box-body>:last-child{margin-bottom:0}
.box-quick{background:var(--blue-bg);border-color:#cfdcec;border-left:5px solid var(--brand)}
.box-quick .box-title{color:var(--brand);text-transform:uppercase;font-size:.8rem;letter-spacing:.08em}
.box-quick .box-body{font-size:1.1rem;font-weight:500;color:var(--brand-dark)}
.box-warning{background:var(--red-bg);border-color:#efc9c6;border-left:5px solid var(--red)}
.box-warning .box-title{color:var(--red)}
.box-note{background:var(--blue-bg);border-color:#cfdcec;border-left:5px solid #4a90c2}
.box-note .box-title{color:#2a5f8f}
.box-tip{background:var(--green-bg);border-color:#c8e3cf;border-left:5px solid var(--green)}
.box-tip .box-title{color:var(--green)}

/* TOC */
.toc{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:1rem 1.3rem;margin:1.6rem 0;font-size:.95rem}
.toc-title{font-weight:800;margin:0 0 .5rem;font-size:.8rem;text-transform:uppercase;letter-spacing:.08em;color:var(--ink-soft)}
.toc ol{margin:0;padding-left:1.3em;columns:2;column-gap:2rem}
.toc li{break-inside:avoid;margin-bottom:.3em}
.toc a{text-decoration:none;color:var(--brand)}
.toc a:hover,.toc a.active{text-decoration:underline;color:var(--accent-dark)}
@media (max-width:600px){.toc ol{columns:1}}

/* CTA */
.cta{border-radius:var(--radius);padding:1.4rem 1.5rem;margin:1.8rem 0;background:linear-gradient(135deg,#f6f1ea,#fbf4ea);border:1px solid #efd9c2}
.cta-title{font-weight:800;font-size:1.15rem;color:var(--brand-dark);margin:0 0 .3rem}
.cta p{margin-bottom:.6rem}
.cta-quote,.cta-heatpump{display:grid;grid-template-columns:1fr auto;gap:.5rem 1.5rem;align-items:center}
.cta-quote .cta-text,.cta-heatpump .cta-text{grid-column:1}
.cta-quote .btn,.cta-heatpump .btn{grid-column:2;grid-row:1;white-space:nowrap}
.cta-small{grid-column:1/-1;font-size:.8rem;color:var(--ink-faint);margin:0}
@media (max-width:640px){.cta-quote,.cta-heatpump{grid-template-columns:1fr}.cta-quote .btn,.cta-heatpump .btn{grid-column:1;grid-row:auto;justify-self:start}}
.cta-soft{background:var(--surface);border-color:var(--line);border-left:5px solid var(--accent)}
.cta-soft p:last-child{margin:0}
.cta-internal{background:var(--surface);border-color:var(--line);padding:1rem 1.3rem}
.cta-internal p:last-child{margin:0}
.cta-inline{font-weight:600;margin:-.6rem 0 1.4rem;font-size:.95rem}
.cta-inline a{color:var(--accent-dark)}

/* Ads */
.ad-slot{min-height:280px;margin:1.8rem 0;background:var(--bg-alt);border-radius:10px;display:flex;align-items:center;justify-content:center;overflow:hidden}
.ad-slot .adsbygoogle{width:100%}

/* FAQ */
.faq{margin-top:2.5rem}
.faq-item{border:1px solid var(--line);border-radius:10px;background:var(--surface);margin-bottom:.6rem}
.faq-item summary{cursor:pointer;padding:.9rem 1.1rem;list-style:none;display:flex;justify-content:space-between;gap:1rem;align-items:center}
.faq-item summary::-webkit-details-marker{display:none}
.faq-item summary::after{content:"+";font-size:1.4rem;color:var(--accent);line-height:1;flex:none}
.faq-item[open] summary::after{content:"\2212"}
.faq-item h3{margin:0;font-size:1.02rem}
.faq-answer{padding:0 1.1rem 1rem;color:var(--ink-soft)}
.faq-answer p:last-child{margin:0}

/* Sources */
.sources{margin-top:2.5rem;font-size:.92rem;color:var(--ink-soft)}
.sources h2{font-size:1.2rem}
.sources-note{font-size:.85rem;color:var(--ink-faint)}

/* Diagram */
.diagram{margin:1.8rem 0;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:1rem}
.diagram svg{width:100%;height:auto}
.diagram figcaption{text-align:left}

/* Calculator */
.calc{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:1.4rem 1.5rem;margin:1.8rem 0}
.calc h2{margin-top:0;border:0;padding:0}
.calc-intro{color:var(--ink-soft);font-size:.95rem}
.calc-form{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:1rem}
.calc-field{display:flex;flex-direction:column;gap:.3rem}
.calc-field label{font-weight:600;font-size:.9rem}
.calc-field select{font:inherit;padding:.55rem .7rem;border:1px solid var(--line);border-radius:8px;background:#fff;color:var(--ink)}
.calc-result{grid-column:1/-1;background:var(--blue-bg);border-radius:10px;padding:1rem 1.2rem}
.calc-result-title{margin:0;font-size:.8rem;text-transform:uppercase;letter-spacing:.08em;color:var(--brand);font-weight:700}
.calc-result-main{font-size:1.8rem;font-weight:800;color:var(--brand-dark);margin:.2rem 0}
.calc-result-note{margin:0;color:var(--ink-soft);font-size:.95rem}
.calc-small{font-size:.82rem;color:var(--ink-faint);margin:1rem 0 0}

/* Related / cluster list */
.related,.cluster-list{padding:1rem 1rem 3rem}
.related h2,.cluster-list h2{margin-top:0}
.cluster-list{border-top:1px solid var(--line);padding-top:2.5rem}
.hub-list{columns:2;column-gap:2rem}
@media (max-width:600px){.hub-list{columns:1}}
.preview-banner{background:#fff3cd;color:#664d03;text-align:center;padding:.5rem 1rem;font-size:.9rem;font-weight:600}

/* Footer */
.site-footer{background:var(--brand-dark);color:#c9d6e6;padding:3rem 0 2rem;margin-top:2rem;font-size:.92rem}
.site-footer a{color:#fff}
.footer-grid{display:grid;grid-template-columns:2fr 1fr 1fr;gap:2rem}
@media (max-width:760px){.footer-grid{grid-template-columns:1fr}}
.footer-brand{font-weight:800;font-size:1.2rem;color:#fff;margin:0 0 .5rem}
.footer-heading{font-weight:700;color:#fff;margin:0 0 .6rem;text-transform:uppercase;letter-spacing:.06em;font-size:.8rem}
.site-footer ul{list-style:none;padding:0;margin:0}
.site-footer li{margin-bottom:.35rem}
.footer-emergency{background:rgba(255,255,255,.08);padding:.7rem .9rem;border-radius:8px}
.footer-legal{border-top:1px solid rgba(255,255,255,.15);margin:2rem 0 0;padding-top:1.2rem;font-size:.82rem;color:#9fb0c6}
.cmp-link{display:none}
.cmp-link.is-available{display:inline}

@media print{.site-header,.site-footer,.cta,.ad-slot,.related{display:none}}