:root{
  --paper:#f7fafa;
  --paper-dim:#eef4f4;
  --ink:#122;
  --ink-soft:#3a4444;
  --line:#d3e0e0;
  --gray:#7a8888;
  --teal:#0d7d78;
  --teal-dim:#4aa39f;
  --max:960px;
}

*{box-sizing:border-box;}
html{scroll-behavior:smooth;}
body{
  margin:0;
  background:var(--paper);
  color:var(--ink);
  font-family:'Inter','Helvetica Neue',sans-serif;
  line-height:1.6;
  -webkit-font-smoothing:antialiased;
}
h1,h2,h3{
  font-family:'Source Serif 4','Georgia',serif;
  font-weight:600;
  letter-spacing:.01em;
}
a{color:var(--teal);text-decoration:none;}
a:hover{color:var(--ink);}
img{max-width:100%;display:block;}

.wrap{max-width:var(--max);margin:0 auto;padding:0 24px;}

/* ---- Header ---- */
header.site{
  border-bottom:1px solid var(--line);
  background:var(--paper);
  position:sticky;top:0;z-index:20;
}
header.site .bar{
  display:flex;align-items:center;justify-content:space-between;
  padding:16px 24px;max-width:var(--max);margin:0 auto;
}
.brand{display:flex;align-items:center;gap:10px;}
.brand .name{
  font-family:'Source Serif 4',serif;
  font-size:1.35rem;letter-spacing:.02em;
  color:var(--ink);
}
.brand .name strong{color:var(--teal);}
nav.primary{display:flex;gap:22px;font-size:.9rem;}
nav.primary a{color:var(--ink-soft);}

/* ---- Hero ---- */
.hero{
  padding:56px 0 40px;
  text-align:center;
  border-bottom:1px solid var(--line);
}
.hero .tag{
  font-size:.78rem;letter-spacing:.14em;text-transform:uppercase;
  color:var(--teal);margin-bottom:14px;display:block;
}
.hero h1{
  font-size:clamp(1.9rem,4.5vw,2.7rem);
  margin:0 0 14px;
  color:var(--ink);
}
.hero p.lede{
  font-size:1.05rem;
  color:var(--ink-soft);
  max-width:620px;margin:0 auto;
}

/* ---- Ad slots ---- */
.ad-slot{
  background:var(--paper-dim);
  border:1px dashed var(--line);
  color:var(--gray);
  font-size:.78rem;
  text-align:center;
  padding:14px;
  margin:0 auto;
}
.ad-slot.top-banner{max-width:var(--max);margin:16px auto;min-height:90px;display:flex;align-items:center;justify-content:center;}
.ad-slot.mid-inline{max-width:680px;margin:40px auto;min-height:250px;display:flex;align-items:center;justify-content:center;}
.ad-slot.footer-ad{max-width:var(--max);margin:16px auto;min-height:90px;display:flex;align-items:center;justify-content:center;}

/* ---- Calculator ---- */
.calc-section{padding:48px 0;}
.calc-card{
  max-width:560px;margin:0 auto;
  background:#fff;
  border:1px solid var(--line);
  border-radius:8px;
  padding:32px;
}
.field{margin-bottom:20px;}
.field label{
  display:block;font-size:.85rem;font-weight:600;
  color:var(--ink-soft);margin-bottom:6px;
}
.field .hint{font-size:.78rem;color:var(--gray);margin-top:4px;}
.field input,.field select{
  width:100%;padding:10px 12px;
  border:1px solid var(--line);border-radius:6px;
  font-family:inherit;font-size:1rem;
  background:var(--paper);color:var(--ink);
}
.field input:focus,.field select:focus{outline:2px solid var(--teal-dim);outline-offset:1px;}
.row-2{display:grid;grid-template-columns:1fr 1fr;gap:16px;}
.unit-toggle{display:flex;gap:8px;margin-bottom:4px;}
.unit-toggle button{
  flex:1;padding:8px;border:1px solid var(--line);background:var(--paper);
  border-radius:6px;cursor:pointer;font-size:.85rem;color:var(--ink-soft);
}
.unit-toggle button.active{background:var(--teal);border-color:var(--teal);color:#fff;}

.btn-calc{
  width:100%;padding:14px;margin-top:8px;
  background:var(--teal);color:#fff;border:none;border-radius:6px;
  font-size:1rem;font-weight:600;cursor:pointer;
}
.btn-calc:hover{background:#0a625e;}

.result-box{
  margin-top:28px;padding:24px;
  background:var(--paper-dim);border-radius:8px;
  display:none;
}
.result-box.show{display:block;}
.result-row{display:flex;justify-content:space-between;padding:8px 0;border-bottom:1px solid var(--line);}
.result-row:last-of-type{border-bottom:none;}
.result-row .label{color:var(--ink-soft);font-size:.9rem;}
.result-row .value{font-weight:700;font-size:1.05rem;}
.result-row .value.corrected{color:var(--teal);}
.category-badge{
  display:inline-block;margin-top:12px;padding:6px 14px;
  border-radius:999px;font-size:.82rem;font-weight:600;
  background:var(--teal);color:#fff;
}
.explanation{margin-top:16px;font-size:.88rem;color:var(--ink-soft);line-height:1.55;}

/* ---- Info sections ---- */
section.info{padding:56px 0;border-top:1px solid var(--line);}
section.info.alt{background:var(--paper-dim);}
.section-head{max-width:680px;margin:0 auto 32px;text-align:center;}
.section-head h2{font-size:1.7rem;margin:0 0 10px;}
.section-head p{color:var(--ink-soft);margin:0;}
.info-body{max-width:680px;margin:0 auto;font-size:.98rem;color:var(--ink-soft);}
.info-body p{margin:0 0 16px;}
.disclaimer{
  max-width:680px;margin:32px auto 0;padding:16px 20px;
  border-left:3px solid var(--teal);background:var(--paper-dim);
  font-size:.85rem;color:var(--ink-soft);
}

/* ---- Footer ---- */
footer.site{
  border-top:1px solid var(--line);
  padding:32px 0;
  font-size:.82rem;color:var(--gray);
}
footer.site .wrap{display:flex;justify-content:space-between;align-items:center;flex-wrap:wrap;gap:14px;}
footer.site a{color:var(--gray);}
footer.site a:hover{color:var(--ink);}

@media (max-width:600px){
  nav.primary{display:none;}
  .row-2{grid-template-columns:1fr;}
  .calc-card{padding:22px;}
}