/* ============================================================
   RegValve.com — SPLIT-SCREEN EDITORIAL THEME (v14, final)
   Sand paper + deep teal + thin hairlines. Quiet, precise.
   ============================================================ */
@import url('https://fonts.googleapis.com/css2?family=Work+Sans:wght@400;500;600;700&display=swap');

:root {
  --sand: #F7F5F0;
  --card: #FFFFFF;
  --ink: #101820;
  --ink-soft: #2A3440;
  --mut: #5B6672;
  --teal: #0F766E;
  --teal-d: #0C5F59;
  --teal-tint: #BFE3DF;
  --teal-wash: #E4F2F0;
  --line: #E4E0D8;
  --line-strong: #CFC9BD;

  /* legacy var aliases (404 page inline styles) */
  --blue-900: var(--ink);
  --gray-600: var(--mut);
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: 'Work Sans', system-ui, sans-serif;
  background: var(--sand);
  color: var(--ink);
  font-size: 16.5px;
  line-height: 1.7;
}
img { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }

.container { max-width: 1160px; margin: 0 auto; padding: 0 30px; }
.section { padding: 56px 0 80px; }

h1, h2, h3, h4 { line-height: 1.22; font-weight: 700; letter-spacing: -.015em; }
h1 { font-size: 40px; }
h2 { font-size: 26px; margin: 40px 0 16px; padding-top: 22px; border-top: 1px solid var(--line-strong); }
h2::before { content: ""; display: inline-block; width: 10px; height: 10px; background: var(--teal); margin-right: 12px; }
h3 { font-size: 19px; margin: 28px 0 10px; }
p { margin: 12px 0; }
ul, ol { margin: 12px 0 12px 26px; }
li { margin: 7px 0; }
li::marker { color: var(--teal); font-weight: 700; }
strong { font-weight: 600; }

/* ---------- header ---------- */
.site-header {
  background: var(--sand);
  border-bottom: 1px solid var(--line-strong);
  position: sticky; top: 0; z-index: 50;
}
.header-inner { display: flex; align-items: center; gap: 28px; height: 72px; }
.brand {
  font-weight: 700; font-size: 21px; letter-spacing: -.01em;
  display: flex; flex-direction: column; line-height: 1.1;
}
.brand span { color: var(--teal); }
.brand small {
  font-size: 9.5px; font-weight: 600; letter-spacing: .22em;
  text-transform: uppercase; color: var(--mut); margin-top: 2px;
}
.nav-toggle {
  display: none; margin-left: auto; background: var(--ink); color: #fff;
  border: 0; border-radius: 6px; font-size: 19px; padding: 8px 14px; cursor: pointer;
}
.main-nav { margin-left: auto; }
.main-nav ul { display: flex; gap: 22px; list-style: none; margin: 0; }
.main-nav a {
  font-size: 13.5px; font-weight: 600; color: var(--mut);
  padding: 26px 0 24px; border-bottom: 2px solid transparent; transition: .15s;
}
.main-nav a:hover { color: var(--teal-d); border-color: var(--teal); }

/* ---------- breadcrumb ---------- */
.breadcrumb {
  padding: 20px 0 0; font-size: 13px; font-weight: 600; color: var(--mut);
}
.breadcrumb a { color: var(--teal-d); border-bottom: 1px solid var(--teal-tint); padding-bottom: 1px; }
.breadcrumb a:hover { border-color: var(--teal); }
.breadcrumb span { margin: 0 8px; color: var(--line-strong); }

/* ---------- article ---------- */
.article { max-width: 800px; }
.article > .container { max-width: 800px; }
.article h1 { margin: 12px 0 4px; }
.article-meta {
  display: flex; flex-wrap: wrap; gap: 8px 20px;
  font-size: 12.5px; font-weight: 600; color: var(--mut);
  margin: 18px 0 12px; padding-bottom: 18px; border-bottom: 1px solid var(--line-strong);
}
.article-meta .reviewed { color: var(--teal-d); }
.article-meta .reviewed::before { content: "✓ "; font-weight: 700; }

/* ---------- callouts ---------- */
.callout {
  background: var(--card); border: 1px solid var(--line);
  border-left: 4px solid var(--teal); border-radius: 0 8px 8px 0;
  padding: 18px 22px; margin: 24px 0; font-size: 15.5px;
}
.callout-warn { border-left-color: var(--ink); background: var(--teal-wash); }

/* ---------- formula ---------- */
.formula {
  background: var(--card); border: 1px solid var(--line-strong); border-radius: 10px;
  text-align: center; font-weight: 600; font-size: 21px;
  padding: 22px 16px; margin: 24px 0;
  box-shadow: 0 14px 30px -22px rgba(16, 24, 32, .35);
}
.formula sub { font-size: 13px; }

/* ---------- tables ---------- */
.var-table, .mfr-table {
  width: 100%; border-collapse: collapse; margin: 20px 0;
  background: var(--card); font-size: 14.5px;
  border: 1px solid var(--line-strong); overflow: hidden;
}
.var-table th, .mfr-table th {
  background: var(--teal-wash); color: var(--teal-d); text-align: left;
  font-size: 12px; font-weight: 700; letter-spacing: .08em; text-transform: uppercase;
  padding: 11px 15px;
}
.var-table td, .mfr-table td { padding: 11px 15px; border-top: 1px solid var(--line); vertical-align: top; }
.mfr-table .tba {
  font-weight: 700; font-size: 11px; letter-spacing: .06em; text-transform: uppercase;
  color: var(--teal-d); background: var(--teal-wash); border-radius: 999px;
  padding: 3px 10px; white-space: nowrap; display: inline-block;
}

/* ---------- reference / next / disclaimer ---------- */
.refs { list-style: none; margin-left: 0; }
.refs li { padding: 9px 0 9px 24px; border-bottom: 1px solid var(--line); position: relative; }
.refs li::before { content: "—"; position: absolute; left: 0; color: var(--teal); font-weight: 700; }
.next-links { margin-top: 38px; }
.next-links ul { list-style: none; margin: 0; }
.next-links a {
  display: block; font-weight: 600; font-size: 15px; padding: 14px 18px; margin: 8px 0;
  background: var(--card); border: 1px solid var(--line); border-radius: 8px; transition: .15s;
}
.next-links a:hover { border-color: var(--teal); background: var(--teal-wash); }
.next-links a::before { content: "→ "; color: var(--teal); font-weight: 700; }
.disclaimer {
  margin-top: 38px; font-size: 13px; color: var(--mut);
  border-top: 1px solid var(--line-strong); padding-top: 16px;
}

/* ---------- cards / grids (tools page) ---------- */
.grid { display: grid; gap: 20px; }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.card {
  background: var(--card); border: 1px solid var(--line); border-radius: 12px;
  padding: 24px 22px; transition: .15s; display: flex; flex-direction: column;
}
.card:hover { border-color: var(--teal); transform: translateY(-3px); box-shadow: 0 20px 36px -24px rgba(16,24,32,.35); }
.card h3 { margin: 0 0 8px; font-size: 17px; }
.card p { font-size: 14px; color: var(--mut); margin: 0; }
.badge {
  display: inline-block; vertical-align: middle; margin-left: 8px;
  background: var(--teal-wash); color: var(--teal-d); font-size: 10.5px; font-weight: 700;
  letter-spacing: .06em; text-transform: uppercase; padding: 3px 10px; border-radius: 999px;
}

/* ---------- chip (404 etc.) ---------- */
.chip {
  display: inline-block; font-weight: 600; font-size: 15px;
  padding: 14px 30px; border-radius: 6px; background: var(--teal); color: #fff; transition: .15s;
}
.chip:hover { background: var(--teal-d); }

/* ---------- footer ---------- */
.site-footer { background: var(--ink); color: #9AA4AE; margin-top: 50px; }
.site-footer .container { padding-top: 50px; padding-bottom: 30px; }
.footer-grid { display: grid; grid-template-columns: 1.4fr 1fr 1fr 1fr; gap: 38px; }
.site-footer h4 { color: #fff; font-size: 14px; margin-bottom: 12px; }
.site-footer h4::after { content: ""; display: block; width: 26px; height: 2px; background: var(--teal); margin-top: 6px; }
.site-footer p { font-size: 13.5px; }
.site-footer ul { list-style: none; margin: 0; }
.site-footer a { display: block; padding: 4px 0; font-size: 13.5px; }
.site-footer a:hover { color: #7FD1C9; }
.footer-note {
  border-top: 1px solid #2A3440; margin-top: 36px; padding-top: 20px;
  font-size: 12px; color: #6E7985; line-height: 1.8;
}

/* ---------- responsive ---------- */
@media (max-width: 980px) {
  .grid-3 { grid-template-columns: 1fr 1fr; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .nav-toggle { display: block; }
  .main-nav { display: none; position: absolute; top: 72px; left: 0; right: 0;
    background: var(--sand); border-bottom: 1px solid var(--line-strong); padding: 8px 30px 20px; }
  .main-nav.open { display: block; }
  .main-nav ul { flex-direction: column; gap: 0; }
  .main-nav a { display: block; padding: 12px 0; border-bottom: 1px solid var(--line); font-size: 15px; }
}
@media (max-width: 600px) {
  .grid-3, .footer-grid { grid-template-columns: 1fr; }
  h1 { font-size: 30px; }
  h2 { font-size: 22px; }
}