/*
Theme Name: Petroleum Engineers
Theme URI: https://petroleumengineers.net
Author: Petroleum Engineers
Description: Minimal classic theme for the petroleum engineering formula library.
Version: 1.0.0
Requires at least: 6.5
Requires PHP: 8.1
Text Domain: penet
*/

:root {
  --brand-50: #f0f9ff;
  --brand-100: #e0f2fe;
  --brand-200: #bae6fd;
  --brand-600: #0284c7;
  --brand-700: #0369a1;
  --brand-800: #075985;
  --brand-950: #082f49;
  --accent: #f97316;
  --accent-50: #fff7ed;
  --accent-700: #c2410c;
  --gray-50: #f9fafb;
  --gray-200: #e5e7eb;
  --gray-300: #d1d5db;
  --gray-500: #6b7280;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-900: #111827;
  --max: 80rem;
  --font: "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", Arial, sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  font-family: var(--font);
  color: var(--gray-900);
  background: #fff;
  line-height: 1.5;
}

a { color: var(--brand-700); text-decoration: none; }
a:hover { text-decoration: underline; }

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

.skip-link {
  position: absolute;
  left: 1rem;
  top: -4rem;
  background: #fff;
  padding: 0.5rem 0.75rem;
  z-index: 10;
}
.skip-link:focus { top: 0.5rem; }

.site-header {
  background: var(--brand-800);
  color: #fff;
  border-bottom: 1px solid rgba(3, 105, 161, 0.5);
}

.header-inner,
.footer-inner,
.container {
  width: min(var(--max), calc(100% - 2rem));
  margin-inline: auto;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 4rem;
}

.brand {
  color: #fff;
  font-size: 1.25rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  text-transform: uppercase;
}
.brand:hover { color: var(--brand-100); text-decoration: none; }

.nav-link {
  color: #fff;
  text-transform: uppercase;
  padding: 0.5rem 0.75rem;
  border-radius: 0.375rem;
}
.nav-link:hover,
.nav-link[aria-current="page"] {
  background: rgba(3, 105, 161, 0.6);
  text-decoration: none;
}

.site-main { flex: 1; }

.site-footer {
  background: var(--brand-950);
  color: var(--brand-100);
  margin-top: 3rem;
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2rem;
  padding: 2rem 0;
}

.site-footer h2 {
  color: #fff;
  font-size: 1.05rem;
  margin: 0 0 0.75rem;
}

.site-footer a { color: var(--brand-200); }
.site-footer ul { list-style: none; margin: 0; padding: 0; }
.site-footer li + li { margin-top: 0.4rem; }
.site-footer p { margin: 0; color: var(--brand-200); font-size: 0.92rem; }

.legal {
  border-top: 1px solid var(--brand-800);
  text-align: center;
  color: #7dd3fc;
  padding: 1.25rem 0 1.5rem;
  margin: 0;
}

.page { padding: 3rem 0; }
.page-narrow { padding: 2rem 0 3rem; }

.hero { text-align: center; margin-bottom: 3.5rem; }
.hero h1 { font-size: clamp(2rem, 4vw, 3rem); margin: 0 0 1rem; }
.lede { font-size: 1.25rem; color: var(--gray-600); max-width: 46rem; margin: 0 auto; }

.stats {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin-bottom: 3.5rem;
}
.stat {
  text-align: center;
  border-radius: 0.5rem;
  padding: 1.5rem;
}
.stat-brand { background: var(--brand-50); }
.stat-accent { background: var(--accent-50); }
.stat strong { display: block; font-size: 2.25rem; line-height: 1.1; }
.stat-brand strong { color: var(--brand-700); }
.stat-accent strong { color: var(--accent-700); }
.stat span { color: var(--gray-600); }

.section-title { font-size: 1.875rem; margin: 0 0 1.5rem; }

.cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}

.card {
  display: block;
  background: #fff;
  border: 1px solid var(--gray-200);
  border-radius: 0.5rem;
  padding: 1.5rem;
  color: inherit;
}
.card:hover {
  border-color: #7dd3fc;
  box-shadow: 0 4px 12px rgba(15, 23, 42, 0.06);
  text-decoration: none;
}
.card h3 { margin: 0 0 0.4rem; color: var(--brand-700); font-size: 1.05rem; }
.card p { margin: 0; color: var(--gray-500); font-size: 0.9rem; }

.cta {
  margin-top: 3.5rem;
  text-align: center;
  background: var(--gray-50);
  border-radius: 0.5rem;
  padding: 2rem;
}
.cta h2 { margin: 0 0 0.5rem; }
.cta p { color: var(--gray-600); margin: 0 0 1.25rem; }

.button {
  display: inline-block;
  background: var(--brand-600);
  color: #fff;
  font-weight: 600;
  padding: 0.75rem 1.25rem;
  border-radius: 0.5rem;
}
.button:hover { background: var(--brand-700); color: #fff; text-decoration: none; }

.layout {
  display: grid;
  grid-template-columns: minmax(0, 3fr) minmax(14rem, 1fr);
  gap: 2rem;
  padding: 2rem 0 3rem;
}

.crumbs { margin: 0 0 1rem; }
.crumbs ol {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem 0.5rem;
  list-style: none;
  padding: 0;
  margin: 0;
  color: var(--gray-600);
  font-size: 0.9rem;
}
.crumbs li { display: flex; align-items: center; gap: 0.5rem; }
.crumbs li + li::before { content: "/"; color: #9ca3af; }
.crumbs [aria-current="page"] { color: var(--gray-900); font-weight: 500; }

.kicker {
  margin: 0 0 0.25rem;
  color: var(--gray-500);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.catalog-head h1,
.entry-title { margin: 0 0 1rem; font-size: 1.875rem; }
.catalog-head hr,
.rule { border: 0; border-top: 1px solid var(--gray-300); margin: 0; }
.count { text-align: right; color: var(--gray-500); font-size: 0.875rem; margin: 0.5rem 0 0; }

.formula-list { display: flex; flex-direction: column; gap: 0.35rem; }
.formula-row { display: flex; gap: 0.75rem; padding: 0.45rem 0; }
.eq-icon { flex: 0 0 auto; margin-top: 0.2rem; color: var(--accent); }
.eq-icon svg { width: 1.25rem; height: 1.25rem; display: block; }
.formula-row h2,
.related-list h3 { margin: 0; font-size: 1.125rem; line-height: 1.35; }
.formula-number { margin: 0.15rem 0 0; color: var(--gray-500); font-size: 0.8rem; }

.pagination { margin-top: 1.5rem; }
.pagination .page-numbers {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  list-style: none;
  margin: 0;
  padding: 0;
}
.pagination .page-numbers a,
.pagination .page-numbers span {
  display: inline-block;
  min-width: 2.25rem;
  padding: 0.35rem 0.65rem;
  border: 1px solid var(--gray-300);
  border-radius: 0.375rem;
  color: var(--gray-700);
  font-size: 0.875rem;
  text-align: center;
  text-decoration: none;
}
.pagination .page-numbers a:hover { border-color: var(--brand-600); color: var(--brand-700); }
.pagination .page-numbers .current {
  background: var(--brand-600);
  border-color: var(--brand-600);
  color: #fff;
  font-weight: 700;
}

.sidebar h2 { margin: 0 0 0.75rem; font-size: 1rem; }
.sidebar ul { list-style: none; margin: 0; padding: 0; }
.sidebar li + li { margin-top: 0.35rem; }
.sidebar a { color: var(--gray-600); font-size: 0.9rem; }
.sidebar a:hover { color: var(--brand-600); }
.sidebar a[aria-current="page"] { color: var(--brand-700); font-weight: 700; }
.sidebar-all {
  display: inline-block;
  margin-top: 1rem;
  padding-top: 1rem;
  border-top: 1px solid var(--gray-200);
  color: var(--brand-600);
  font-size: 0.9rem;
  font-weight: 600;
}

.formula-number-line { margin: 0 0 1rem; color: var(--gray-600); }
.formula-content h1 { font-size: 2rem; margin: 0 0 1rem; }
.formula-content h2 { font-size: 1.5rem; margin: 2rem 0 0.75rem; }
.formula-content p { margin: 0 0 1rem; color: var(--gray-700); }
.formula-content ul, .formula-content ol { margin: 0 0 1rem; padding-left: 1.4rem; }
.formula-content li + li { margin-top: 0.35rem; }
.formula-content a { color: #2563eb; }
.katex { font-size: 1.1em; }
.katex-display { margin: 1.25rem 0; overflow-x: auto; overflow-y: hidden; }

.related h2 { font-size: 1.25rem; margin: 0 0 0.75rem; }
.related { margin-top: 1.5rem; }
.empty { color: var(--gray-500); text-align: center; padding: 2rem 0; }

@media (max-width: 900px) {
  .cards, .footer-grid, .layout, .stats { grid-template-columns: 1fr; }
  .layout { gap: 2rem; }
}