/* AirFilterKits.com — "Pleat & Tape" design system
   Subject-grounded: painter's-tape blue (#1565AE — the tape that holds every CR box together),
   filter-media whites, pleated zigzag dividers, end-cap-label spec cards.
   Type: system stack (zero font requests), tabular numerals for sizes and figures. */

:root{
  --ink:#1F2A2E;
  --muted:#5A6A70;
  --paper:#F5F8F8;
  --card:#FFFFFF;
  --rule:#D8E1E3;
  --tape:#1565AE;
  --tape-dark:#0E4A7E;
  --tape-bg:#E8F1FA;
  --air:#0E7C9C;
  --alert:#8A4B08;
  --alert-bg:#FAF2E5;
  --max:62rem;
  --radius:6px;
}

*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}

body{
  margin:0;
  background:var(--paper);
  color:var(--ink);
  font-family:ui-sans-serif,system-ui,-apple-system,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  font-size:1.0625rem;
  line-height:1.7;
}

img,svg{max-width:100%;height:auto}

a{color:var(--tape);text-underline-offset:2px}
a:hover{color:var(--tape-dark)}
a:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible{
  outline:3px solid var(--tape);outline-offset:2px;border-radius:2px;
}

.skip{position:absolute;left:-9999px;top:0;background:var(--ink);color:#fff;padding:.6rem 1rem;z-index:100}
.skip:focus{left:0}

/* ---------- Header ---------- */
.site-head{background:var(--card);border-bottom:1px solid var(--rule)}
.site-head .wrap{
  max-width:var(--max);margin:0 auto;padding:.85rem 1.25rem;
  display:flex;flex-wrap:wrap;align-items:center;gap:.75rem 1.5rem;
}
.brand{
  font-weight:800;font-size:1.15rem;letter-spacing:-.02em;
  color:var(--ink);text-decoration:none;display:inline-flex;align-items:center;gap:.5rem;
}
.brand:hover{color:var(--ink)}
.brand .pleat-mark{display:inline-block;width:1.5rem;height:1.5rem;flex:none}
.site-nav{margin-left:auto}
.site-nav ul{list-style:none;margin:0;padding:0;display:flex;flex-wrap:wrap;gap:.25rem .35rem}
.site-nav a{display:block;padding:.35rem .65rem;border-radius:var(--radius);text-decoration:none;font-size:.92rem;font-weight:600;color:var(--ink)}
.site-nav a:hover{background:var(--paper)}
.site-nav a[aria-current="page"]{background:var(--tape);color:#fff}

/* ---------- Layout & type ---------- */
main{max-width:var(--max);margin:0 auto;padding:0 1.25rem 3rem}
.content-narrow{max-width:46rem}

h1{font-size:clamp(1.7rem,4.5vw,2.5rem);line-height:1.15;letter-spacing:-.025em;font-weight:800;margin:1.6rem 0 .5rem}
h2{font-size:1.45rem;letter-spacing:-.015em;font-weight:750;margin:2.4rem 0 .6rem}
h3{font-size:1.12rem;font-weight:700;margin:1.6rem 0 .4rem}
p{margin:.7rem 0}
.lede{font-size:1.15rem;color:var(--muted);max-width:44rem}
.kicker{text-transform:uppercase;letter-spacing:.09em;font-size:.78rem;font-weight:700;color:var(--muted);margin:1.8rem 0 0}
.byline{font-size:.88rem;color:var(--muted);margin:.2rem 0 1rem}
.byline strong{color:var(--ink)}

/* Pleated zigzag divider — the site's recurring motif */
.pleat{
  border:0;height:10px;margin:2.6rem 0;background:
    linear-gradient(135deg,var(--rule) 25%,transparent 25%) 0 0/16px 10px,
    linear-gradient(225deg,var(--rule) 25%,transparent 25%) 0 0/16px 10px;
  background-repeat:repeat-x;opacity:.9;
}

/* ---------- Filter-label card (signature element) ----------
   Styled like the printed end-cap of a pleated filter: thick frame top,
   huge size figure, MERV chip. */
.label-card{
  background:var(--card);
  border:1px solid var(--rule);
  border-top:8px solid var(--ink);
  border-radius:4px;
  padding:1rem 1.2rem 1.05rem;
  box-shadow:0 2px 0 rgba(31,42,46,.08);
}
.label-card .lc-head{
  font-size:.78rem;font-weight:700;text-transform:uppercase;letter-spacing:.09em;
  color:var(--muted);display:flex;justify-content:space-between;gap:.5rem;align-items:center;
}
.label-card .lc-figure{
  font-variant-numeric:tabular-nums;
  font-weight:800;font-size:clamp(1.9rem,5vw,2.6rem);line-height:1.08;
  letter-spacing:-.02em;color:var(--air);margin:.18rem 0 .1rem;
}
.label-card .lc-figure small{font-size:48%;font-weight:700;color:var(--ink);letter-spacing:0}
.label-card .lc-sub{font-size:.9rem;color:var(--muted);margin:0}
.label-card .lc-sub strong{color:var(--ink)}
.label-grid{display:grid;gap:1rem;margin:1.6rem 0 .4rem;grid-template-columns:repeat(auto-fit,minmax(15rem,1fr))}
a.label-card{display:block;text-decoration:none;color:inherit;transition:transform .12s ease}
a.label-card:hover{transform:translateY(-3px);box-shadow:0 5px 0 rgba(31,42,46,.12)}
.label-hero{max-width:30rem;margin:1.4rem 0}

/* MERV chip */
.merv{
  display:inline-block;background:var(--ink);color:#fff;
  font-size:.72rem;font-weight:800;letter-spacing:.06em;
  padding:.18rem .55rem;border-radius:3px;text-transform:uppercase;
}
.merv.m13{background:var(--air)}

/* ---------- Notices (tape strip) ---------- */
.notice{
  background:var(--tape-bg);border-left:6px solid var(--tape);
  padding:.8rem 1rem;border-radius:0 var(--radius) var(--radius) 0;
  font-size:.95rem;margin:1.2rem 0;
}
.notice strong{color:var(--tape-dark)}
.notice.alert{background:var(--alert-bg);border-left-color:var(--alert)}
.notice.alert strong{color:var(--alert)}
.verified{
  display:inline-block;background:var(--tape-bg);color:var(--tape-dark);
  font-size:.8rem;font-weight:700;padding:.2rem .6rem;border-radius:999px;
  text-transform:uppercase;letter-spacing:.05em;
}
.affiliate-note{
  font-size:.85rem;color:var(--muted);background:var(--card);
  border:1px dashed var(--rule);border-radius:var(--radius);padding:.6rem .8rem;margin:.8rem 0;
}

/* ---------- Tables ---------- */
.table-scroll{overflow-x:auto;margin:1rem 0}
table{border-collapse:collapse;width:100%;background:var(--card);font-size:.95rem;border:1px solid var(--rule)}
caption{text-align:left;font-weight:700;padding:.6rem .8rem;font-size:1rem;background:var(--card);border:1px solid var(--rule);border-bottom:0}
th,td{padding:.6rem .8rem;text-align:left;border-bottom:1px solid var(--rule);vertical-align:top}
thead th{background:var(--ink);color:#fff;font-size:.82rem;text-transform:uppercase;letter-spacing:.05em;border-bottom:0}
td.num,th.num{text-align:right;font-variant-numeric:tabular-nums;font-weight:600}
tbody tr:last-child td{border-bottom:0}
tr.pick td{background:var(--tape-bg)}
tr.pick td:first-child::after{
  content:"good default";display:inline-block;margin-left:.5rem;
  font-size:.68rem;font-weight:800;text-transform:uppercase;letter-spacing:.05em;color:var(--tape-dark);
}

/* ---------- Tool (size decoder) ---------- */
.tool{background:var(--card);border:1px solid var(--rule);border-radius:10px;padding:1.4rem;margin:1.4rem 0}
.tool h2,.tool h3{margin-top:0}
.tool-row{display:flex;flex-wrap:wrap;gap:1rem;margin:.9rem 0}
.field{flex:1 1 11rem;min-width:0}
.field label{display:block;font-size:.85rem;font-weight:700;margin-bottom:.3rem}
.field input,.field select{
  width:100%;padding:.6rem .7rem;font-size:1.05rem;font-variant-numeric:tabular-nums;
  border:2px solid var(--ink);border-radius:var(--radius);background:#fff;color:var(--ink);font-family:inherit;
}
.tool button{
  background:var(--tape);color:#fff;border:0;border-radius:var(--radius);
  padding:.7rem 1.4rem;font-size:1rem;font-weight:700;cursor:pointer;font-family:inherit;
}
.tool button:hover{background:var(--tape-dark)}
.tool-result{margin-top:1.1rem;padding:1rem 1.1rem;border-radius:var(--radius);background:var(--tape-bg);border:1px solid var(--tape);display:none}
.tool-result.show{display:block}
.tool-result .big{font-size:1.55rem;font-weight:800;color:var(--tape-dark);font-variant-numeric:tabular-nums}
.tool-result .detail{font-size:.92rem;margin:.4rem 0 0}
.tool-note{font-size:.85rem;color:var(--muted);margin-top:.8rem}

/* ---------- Steps (build guide) ---------- */
.steps{counter-reset:step;list-style:none;margin:1.2rem 0;padding:0}
.steps li{
  counter-increment:step;position:relative;background:var(--card);
  border:1px solid var(--rule);border-radius:var(--radius);
  padding:.95rem 1.1rem .95rem 3.4rem;margin:.7rem 0;
}
.steps li::before{
  content:counter(step);position:absolute;left:.9rem;top:.9rem;
  width:1.7rem;height:1.7rem;border-radius:50%;background:var(--tape);color:#fff;
  font-weight:800;display:flex;align-items:center;justify-content:center;font-size:.95rem;
}
.steps li strong:first-child{display:block;margin-bottom:.15rem}

/* ---------- FAQ ---------- */
.faq details{background:var(--card);border:1px solid var(--rule);border-radius:var(--radius);padding:0;margin:.6rem 0}
.faq summary{cursor:pointer;font-weight:700;padding:.85rem 1rem;list-style:none;position:relative}
.faq summary::-webkit-details-marker{display:none}
.faq summary::after{content:"+";position:absolute;right:1rem;top:50%;transform:translateY(-50%);font-weight:800;color:var(--tape);font-size:1.2rem}
.faq details[open] summary::after{content:"–"}
.faq .faq-body{padding:0 1rem .9rem}

/* ---------- Sources / footer ---------- */
.sources{background:var(--card);border:1px solid var(--rule);border-radius:var(--radius);padding:1rem 1.2rem;font-size:.92rem;margin:1.6rem 0}
.sources h2,.sources h3{margin-top:0;font-size:1rem;text-transform:uppercase;letter-spacing:.06em}
.sources ul{margin:.4rem 0 0;padding-left:1.2rem}
.sources li{margin:.35rem 0}

.disclaimer{font-size:.85rem;color:var(--muted)}

.site-foot{border-top:1px solid var(--rule);background:var(--card);margin-top:3rem}
.site-foot .wrap{max-width:var(--max);margin:0 auto;padding:1.6rem 1.25rem;font-size:.88rem;color:var(--muted)}
.site-foot nav ul{list-style:none;margin:.5rem 0 0;padding:0;display:flex;flex-wrap:wrap;gap:.3rem 1.1rem}
.site-foot a{color:var(--tape)}

/* ---------- Utility ---------- */
.grid-2{display:grid;gap:1.2rem;grid-template-columns:repeat(auto-fit,minmax(17rem,1fr))}
.tag-row{display:flex;flex-wrap:wrap;gap:.4rem;margin:.8rem 0}
.tag-row a{font-size:.85rem;font-weight:600;text-decoration:none;color:var(--ink);border:1px solid var(--rule);background:var(--card);border-radius:999px;padding:.3rem .8rem}
.tag-row a:hover{border-color:var(--tape);color:var(--tape)}
.breadcrumb{font-size:.85rem;color:var(--muted);margin:1.2rem 0 0}
.breadcrumb ol{list-style:none;margin:0;padding:0;display:flex;flex-wrap:wrap;gap:.35rem}
.breadcrumb li+li::before{content:"›";margin-right:.35rem;color:var(--rule)}
.breadcrumb a{color:var(--muted)}

@media (max-width:40rem){.site-nav{margin-left:0;width:100%}body{font-size:1rem}}
@media (prefers-reduced-motion:reduce){*{transition:none !important;animation:none !important}}
@media print{.site-head,.site-foot,.tool button,.tag-row{display:none}body{background:#fff}.label-card{box-shadow:none}}