/* DIY HVAC Tools — one stylesheet. Tokens first. */
:root{
  --paper:#F2F4F6; --paper-2:#E8ECF0; --card:#FFFFFF;
  --ink:#1B2430; --ink-2:#4A5563; --ink-3:#7A8493; --line:#D5DAE0; --line-2:#C2C9D2;
  --panel:#1A1D21; --panel-2:#24282E;
  --led:#FFB428; --led-glow:rgba(255,180,40,.55); --led-off:rgba(255,190,80,.10);
  --link:#1F56C9; --link-2:#143C8F;
  --fault:#C43D2F; --fault-bg:#FBE9E6; --prot:#9A6410; --prot-bg:#FFF2D9; --status:#1B7F6B; --status-bg:#DDF3EC;
  --easy:#1B7F6B; --mod:#9A6410; --pro:#C43D2F;
  --wrap:72rem; --read:46rem; --r:.5rem;
  --font:"Atkinson Hyperlegible Next","Atkinson Hyperlegible",system-ui,-apple-system,"Segoe UI",Roboto,sans-serif;
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--paper);color:var(--ink);font:400 17px/1.55 var(--font);font-feature-settings:"ss01"}
a{color:var(--link);text-underline-offset:.15em}
a:hover{color:var(--link-2)}
h1,h2,h3{line-height:1.15;margin:0 0 .5em;font-weight:800;letter-spacing:-.01em}
h1{font-size:clamp(1.85rem,1.2rem + 2.4vw,2.6rem)}
h2{font-size:1.35rem;margin-top:2.2em}
h3{font-size:1.08rem;font-weight:700}
p{margin:0 0 1em}
ul,ol{padding-left:1.3em}
li{margin:.3em 0}
b,strong{font-weight:700}
.wrap{max-width:var(--wrap);margin:0 auto;padding:0 1.25rem}
.muted{color:var(--ink-2)}
.sr{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0)}
.skip{position:absolute;left:-999px;top:0;background:var(--ink);color:#fff;padding:.5em 1em;z-index:10}
.skip:focus{left:1rem}
:focus-visible{outline:3px solid var(--led);outline-offset:2px}

/* header / footer */
.top{background:var(--card);border-bottom:1px solid var(--line)}
.top-in{display:flex;align-items:center;justify-content:space-between;gap:1rem;min-height:3.75rem}
.brand{display:inline-flex;align-items:center;gap:.6rem;color:var(--ink);text-decoration:none;font-weight:800;font-size:1.1rem;letter-spacing:-.01em}
.brand-mark .seg{font-size:11px;padding:.3em .35em;border-radius:.25em}
.nav{display:flex;gap:1.25rem}
.nav a{color:var(--ink-2);text-decoration:none;font-weight:500}
.nav a:hover{color:var(--ink)}
@media (max-width:640px){.brand{font-size:1rem}.brand-name{white-space:nowrap}.nav{gap:.8rem;font-size:.9rem}.nav a{white-space:nowrap}.top-in{gap:.6rem}}
.foot{margin-top:4rem;border-top:1px solid var(--line);background:var(--paper-2);color:var(--ink-2);font-size:.92rem}
.foot-in{padding:2rem 1.25rem}
.foot-links a{margin-right:1.25rem}
.foot-copy{margin:0;color:var(--ink-3)}

/* seven-segment readout */
.seg{display:inline-flex;align-items:center;gap:.16em;font-size:40px;line-height:1;padding:.32em .45em;background:var(--panel);border-radius:.16em;box-shadow:inset 0 .06em .3em rgba(0,0,0,.7),0 0 0 1px #0a0b0d;vertical-align:middle}
.seg .dg{position:relative;display:inline-block;width:.6em;height:1em;flex:none}
.seg .dg i{position:absolute;display:block;background:var(--led-off);border-radius:.05em}
.seg .dg i.a,.seg .dg i.g,.seg .dg i.d{left:.1em;right:.1em;height:.11em}
.seg .dg i.a{top:0}.seg .dg i.g{top:calc(50% - .055em)}.seg .dg i.d{bottom:0}
.seg .dg i.f,.seg .dg i.b,.seg .dg i.e,.seg .dg i.c{width:.11em;height:calc(50% - .085em)}
.seg .dg i.f{left:0;top:.06em}.seg .dg i.b{right:0;top:.06em}.seg .dg i.e{left:0;bottom:.06em}.seg .dg i.c{right:0;bottom:.06em}
.seg .dg i.on{background:var(--led);box-shadow:0 0 .1em var(--led-glow)}
.seg .dg.gap{width:.3em}
.seg .dg.colon{width:.2em;display:inline-flex;flex-direction:column;justify-content:center;gap:.22em}
.seg .dg.colon i{position:static;width:.11em;height:.11em;border-radius:50%;background:var(--led);box-shadow:0 0 .1em var(--led-glow);margin:0 auto}
.seg .dg.txt{width:auto;color:var(--led);font:700 .9em/1 ui-monospace,Menlo,monospace;text-shadow:0 0 .12em var(--led-glow);padding:0 .05em}
.seg.hero{font-size:clamp(56px,6vw,84px)}
.seg.big{font-size:clamp(52px,7vw,80px)}
.seg.row{font-size:14px;padding:.25em .35em;margin-right:.6em;border-radius:.2em}

/* lookup form */
.lookup{background:var(--card);border:1px solid var(--line);border-radius:var(--r);padding:1.25rem;box-shadow:0 1px 2px rgba(27,36,48,.06)}
.lookup-readout{display:flex;justify-content:center;margin-bottom:1.1rem}
.lookup-fields{display:grid;grid-template-columns:1fr 1fr auto;gap:.75rem;align-items:end}
.field{display:flex;flex-direction:column;gap:.3rem;font-weight:500;font-size:.95rem;color:var(--ink-2)}
.field select,.field input{font:inherit;font-size:1.05rem;color:var(--ink);padding:.6em .7em;border:1px solid var(--line-2);border-radius:.4rem;background:#fff;min-width:0;width:100%}
.field input{text-transform:uppercase;letter-spacing:.08em;font-weight:700}
.field input::placeholder{text-transform:none;letter-spacing:0;font-weight:400;color:var(--ink-3)}
.btn{font:inherit;font-weight:700;font-size:1.05rem;padding:.65em 1.2em;border:0;border-radius:.4rem;background:var(--panel);color:var(--led);cursor:pointer;white-space:nowrap}
.btn:hover{background:var(--panel-2)}
.lookup-hint{margin:.9rem 0 0;font-size:.92rem;color:var(--ink-2)}
.lookup-hint .chips{margin-top:.5rem}
.lookup.compact{margin:1.5rem 0 2rem}
.lookup.compact .lookup-readout{display:none}
@media (max-width:640px){.lookup-fields{grid-template-columns:1fr}.btn{width:100%}}

/* home */
.hero{background:linear-gradient(180deg,var(--card),var(--paper));border-bottom:1px solid var(--line);padding:2.5rem 0 2rem}
.hero h1{max-width:34ch}
.hero .lede{max-width:60ch}
.hero-meta{margin:1rem 0 0;color:var(--ink-2);font-size:.95rem}
.lede{font-size:1.15rem;color:var(--ink-2);max-width:65ch}
.group-h{margin:1.4rem 0 .6rem;color:var(--ink-2);font-weight:700;font-size:.95rem}
.cards{display:grid;grid-template-columns:repeat(auto-fill,minmax(11.5rem,1fr));gap:.75rem}
@media (max-width:640px){.cards{grid-template-columns:repeat(2,1fr);gap:.5rem}.card{padding:.7rem .8rem}}
.card{display:flex;flex-direction:column;gap:.15rem;padding:.9rem 1rem;background:var(--card);border:1px solid var(--line);border-radius:var(--r);color:var(--ink);text-decoration:none}
.card:hover{border-color:var(--ink-3)}
.card b{font-size:1.05rem}
.card span{color:var(--ink-2);font-size:.9rem}
.card small{color:var(--ink-3);font-size:.8rem;letter-spacing:.04em}
.chips{display:flex;flex-wrap:wrap;gap:.5rem;margin:.5rem 0 1rem}
.chip{display:inline-flex;flex-direction:column;gap:.05rem;padding:.5rem .75rem;background:var(--card);border:1px solid var(--line);border-radius:.4rem;color:var(--ink);text-decoration:none;max-width:16rem}
.chip:hover{border-color:var(--ink-3)}
.chip b{font-size:.95rem;letter-spacing:.03em}
.chip span{font-size:.82rem;color:var(--ink-2);line-height:1.3}
.explain{margin-bottom:2rem}
.explain-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(16rem,1fr));gap:1.25rem 2rem}
.explain-grid p{margin:0;color:var(--ink-2)}
.families li{margin:.45em 0}

/* breadcrumbs */
.crumbs{margin:1rem 0 1.25rem;font-size:.9rem}
.crumbs ol{list-style:none;padding:0;margin:0;display:flex;flex-wrap:wrap;gap:.35rem}
.crumbs li+li::before{content:"›";color:var(--ink-3);margin-right:.35rem}
.crumbs a{color:var(--ink-2)}
.crumbs [aria-current]{color:var(--ink);font-weight:700}
.page-head{margin:1rem 0}

/* code page */
.code{max-width:var(--read)}
.code-hero{display:flex;gap:1.5rem;align-items:flex-start;margin:.5rem 0 1.5rem}
.code-hero .seg{flex:none}
.code-hero-text h1{margin-bottom:.35rem}
.code-hero-text .lede{color:var(--ink);font-weight:500;margin-bottom:.8rem}
.aka{color:var(--ink-2);font-weight:400}
.facts{list-style:none;padding:0;margin:0;display:flex;flex-wrap:wrap;gap:.5rem}
.fact{display:flex;flex-direction:column;padding:.4rem .7rem;border:1px solid var(--line);border-radius:.4rem;background:var(--card);font-weight:700;font-size:.92rem}
.fact span{font-weight:400;font-size:.78rem;color:var(--ink-2)}
.fact-fault{border-color:var(--fault);background:var(--fault-bg)}
.fact-protection{border-color:var(--prot);background:var(--prot-bg)}
.fact-status{border-color:var(--status);background:var(--status-bg)}
.fact-diy-easy{color:var(--easy)}.fact-diy-moderate{color:var(--mod)}.fact-diy-pro{color:var(--pro)}
@media (max-width:640px){.code-hero{flex-direction:column;gap:1rem}}
.answer{padding:1.25rem 1.4rem;background:var(--card);border-left:4px solid var(--led);border-radius:0 var(--r) var(--r) 0;margin-top:1.5rem}
.answer h2{margin-top:0}
.answer p:last-child{margin-bottom:0}
.type-note{color:var(--ink-2);font-size:.95rem}
.causes li,.steps li{margin:.5em 0}
.steps{counter-reset:s;list-style:none;padding:0}
.steps li{position:relative;padding-left:2.4rem;min-height:1.9rem}
.steps li::before{counter-increment:s;content:counter(s);position:absolute;left:0;top:.05em;width:1.7rem;height:1.7rem;border-radius:50%;background:var(--ink);color:#fff;font-weight:700;font-size:.9rem;display:flex;align-items:center;justify-content:center}
.diy-note{color:var(--ink-2)}
.safety{padding:.75rem 1rem;background:var(--prot-bg);border:1px solid #E8CFA0;border-radius:.4rem;font-size:.95rem}
.replace{margin-top:2.2rem;padding:1.25rem 1.4rem;background:var(--panel);color:#E6E9EE;border-radius:var(--r)}
.replace h2{margin-top:0;color:#fff}
.replace p{color:#C9CFD8}
.replace-links{list-style:none;padding:0;margin:0;display:grid;grid-template-columns:repeat(auto-fit,minmax(14rem,1fr));gap:.75rem}
.replace-links li{display:flex;flex-direction:column;gap:.15rem;padding:.75rem .9rem;background:var(--panel-2);border-radius:.4rem}
.replace-links a{color:var(--led);font-weight:700;text-decoration:none}
.replace-links a:hover{text-decoration:underline}
.replace-links span{font-size:.88rem;color:#AEB6C2}
.elsewhere{list-style:none;padding:0}
.elsewhere li{padding:.35rem 0;border-bottom:1px solid var(--line)}
.more{font-weight:700}
.faq{border:1px solid var(--line);border-radius:.4rem;background:var(--card);margin:.5rem 0;padding:0 1rem}
.faq summary{cursor:pointer;font-weight:700;padding:.75rem 0}
.faq p{color:var(--ink-2);margin:0 0 .9rem}
.sources{color:var(--ink-2);font-size:.95rem}

/* brand page */
.brand-page .lede{max-width:70ch}
.filter{display:block;margin:.5rem 0 1rem;max-width:26rem}
.filter input{font:inherit;padding:.55em .8em;border:1px solid var(--line-2);border-radius:.4rem;width:100%;background:#fff}
.table-wrap{overflow-x:auto;border:1px solid var(--line);border-radius:var(--r);background:var(--card)}
.codes{width:100%;border-collapse:collapse;font-size:.97rem}
.codes th{text-align:left;font-size:.82rem;color:var(--ink-2);font-weight:700;padding:.6rem .8rem;border-bottom:1px solid var(--line);background:var(--paper-2)}
.codes td{padding:.55rem .8rem;border-bottom:1px solid var(--line);vertical-align:middle}
.codes tr:last-child td{border-bottom:0}
.codes tr[hidden]{display:none}
.c-code a{display:inline-flex;align-items:center;color:var(--ink);text-decoration:none;font-weight:800;letter-spacing:.03em;white-space:nowrap}
.c-title a{color:var(--ink);text-decoration:none}
.c-title a:hover,.c-code a:hover{color:var(--link)}
.tag{display:inline-block;font-size:.78rem;font-weight:700;padding:.15em .55em;border-radius:1em;white-space:nowrap}
.tag-fault{background:var(--fault-bg);color:var(--fault)}.tag-protection{background:var(--prot-bg);color:var(--prot)}.tag-status{background:var(--status-bg);color:var(--status)}
.tag-diy-easy{background:var(--status-bg);color:var(--easy)}.tag-diy-moderate{background:var(--prot-bg);color:var(--mod)}.tag-diy-pro{background:var(--fault-bg);color:var(--pro)}
.empty{padding:1rem;background:var(--card);border:1px solid var(--line);border-radius:var(--r)}
@media (max-width:640px){.codes .c-diy{display:none}.seg.row{display:none}}

/* prose */
.prose{max-width:var(--read)}
.prose h2{margin-top:1.8em}

/* lookup results */
.results{list-style:none;padding:0;margin:1rem 0}
.results li{margin:.4rem 0}
.results a{font-weight:700}

@media (prefers-reduced-motion:no-preference){.seg .dg i{transition:background .12s,box-shadow .12s}}

/* multi-meaning codes */
.variant-nav{margin:1.25rem 0 .5rem}
.variant-nav ol{list-style:none;padding:0;margin:0;display:grid;grid-template-columns:repeat(auto-fit,minmax(14rem,1fr));gap:.6rem}
.variant-nav a{display:flex;flex-direction:column;gap:.1rem;padding:.7rem .9rem;background:var(--card);border:1px solid var(--line-2);border-left:4px solid var(--led);border-radius:.4rem;color:var(--ink);text-decoration:none}
.variant-nav a:hover{border-color:var(--ink-3);border-left-color:var(--led)}
.variant-nav b{font-size:.95rem}
.variant-nav span{font-size:.88rem;color:var(--ink-2)}
.variant{margin-top:2rem;padding-top:1rem;border-top:2px solid var(--line-2)}
.variant-h{margin-top:0}
.variant .lede{color:var(--ink);font-weight:500;margin-bottom:.8rem}
.variant .facts{margin-bottom:.5rem}
.variant h3{margin-top:1.6em;font-size:1.15rem}
.variant .answer h3{margin-top:0}

/* footer columns, tools cards */
.foot-cols{display:grid;grid-template-columns:repeat(auto-fit,minmax(12rem,1fr));gap:1.25rem 2rem;margin:1.25rem 0}
.foot-h{font-size:.85rem;margin:0 0 .4rem;color:var(--ink)}
.foot-cols ul{list-style:none;padding:0;margin:0}
.foot-cols li{margin:.25rem 0}
.cards.tools{grid-template-columns:repeat(auto-fill,minmax(15rem,1fr))}
.cards.tools .card span{white-space:normal}