@import url('https://fonts.googleapis.com/css2?family=Playfair+Display:ital,wght@0,400;0,700;1,400&family=Source+Sans+3:wght@400;500&family=Source+Code+Pro:wght@400;500&display=swap');

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  /* Background & surface */
  --color-bg: #EDF4FB;
  --color-surface: #ffffff;

  /* Borders */
  --color-border: rgba(30,80,160,0.12);
  --color-border-strong: rgba(30,80,160,0.22);

  /* Text */
  --color-text-primary: #0f1f3d;
  --color-text-secondary: #2e4a72;
  --color-text-muted: #6b87a8;

  /* Accent */
  --color-accent: #1a5fb4;
  --color-accent-bg: #ddeaf8;

  /* Fonts */
  --font-serif: 'Playfair Display', Georgia, serif;
  --font-sans: 'Source Sans 3', system-ui, sans-serif;
  --font-mono: 'Source Code Pro', monospace;

  /* Level badge colours — used on both index and module pages */
  --beg-bg: #d4edda;
  --beg-text: #1a5c2e;
  --int-bg: #fde9c8;
  --int-text: #7a3e05;
  --adv-bg: #fcd9d0;
  --adv-text: #7a2010;
  --apl-bg: #cce0f5;
  --apl-text: #0a3d6b;
}

/* ─── BASE ──────────────────────────────────────────────── */
body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text-primary);
  line-height: 1.7;
  min-height: 100vh;
  font-size: 17px;
}

/* ─── NAV ───────────────────────────────────────────────── */
nav {
  position: sticky;
  top: 0;
  background: rgba(237,244,251,0.94);
  backdrop-filter: blur(8px);
  border-bottom: 0.5px solid var(--color-border);
  z-index: 100;
  padding: 0 2rem;
}
.nav-inner {
  max-width: 900px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
}
.nav-brand {
  font-family: var(--font-serif);
  font-size: 18px;
  font-weight: 700;
  color: var(--color-text-primary);
  text-decoration: none;
}
.nav-links { display: flex; gap: 1.5rem; list-style: none; }
.nav-links a {
  font-size: 15px;
  color: var(--color-text-muted);
  text-decoration: none;
  transition: color 0.15s;
}
.nav-links a:hover { color: var(--color-text-primary); }

/* ─── MAIN WRAPPER ──────────────────────────────────────── */
main {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 2rem 6rem;
}

/* ─── LANDING PAGE HERO ─────────────────────────────────── */
.hero {
  text-align: center;
  padding: 5rem 1rem 4rem;
  border-bottom: 0.5px solid var(--color-border);
}
.hero-eyebrow {
  font-size: 13px;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: 1.25rem;
}
.hero-title {
  font-family: var(--font-serif);
  font-size: clamp(44px, 6vw, 62px);
  font-weight: 700;
  color: var(--color-text-primary);
  line-height: 1.08;
  margin-bottom: 1.25rem;
  letter-spacing: -0.01em;
}
.hero-title em { font-style: italic; font-weight: 400; }
.hero-sub {
  font-size: 18px;
  color: var(--color-text-secondary);
  max-width: 520px;
  margin: 0 auto 2.5rem;
  line-height: 1.65;
}
.hero-stats { display: flex; justify-content: center; gap: 3.5rem; }
.hero-stat-num {
  font-family: var(--font-serif);
  font-size: 34px;
  font-weight: 700;
  color: var(--color-text-primary);
  display: block;
  line-height: 1;
}
.hero-stat-lbl {
  font-size: 14px;
  color: var(--color-text-muted);
  letter-spacing: 0.04em;
  margin-top: 5px;
  display: block;
}

/* ─── LANDING PAGE CONTENT TABLE ────────────────────────── */
.level-row { display: grid; grid-template-columns: 120px 1fr; }
.level-col {
  padding: 2.5rem 1.5rem 2.5rem 0;
  border-right: 0.5px solid var(--color-border);
  display: flex;
  align-items: flex-start;
  justify-content: flex-end;
}
.level-badge {
  writing-mode: vertical-lr;
  transform: rotate(180deg);
  font-size: 12px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  font-weight: 500;
  padding: 8px 6px;
  border-radius: 4px;
}
.badge-beg { background: var(--beg-bg); color: var(--beg-text); }
.badge-int { background: var(--int-bg); color: var(--int-text); }
.badge-adv { background: var(--adv-bg); color: var(--adv-text); }
.badge-apl { background: var(--apl-bg); color: var(--apl-text); }

.cats-col {
  padding: 2.5rem 0 2.5rem 2.5rem;
  border-bottom: 0.5px solid var(--color-border);
}
.level-row:last-child .cats-col { border-bottom: none; }

.cat { margin-bottom: 2.5rem; }
.cat:last-child { margin-bottom: 0; }
.cat-header { display: flex; align-items: baseline; gap: 12px; margin-bottom: 0.4rem; }
.cat-name {
  font-family: var(--font-serif);
  font-size: 22px;
  font-weight: 400;
  color: var(--color-text-primary);
}
.cat-count { font-size: 13px; color: var(--color-text-muted); }
.cat-desc { font-size: 15px; color: var(--color-text-muted); margin-bottom: 0.75rem; }

.modules-list { font-size: 16px; color: var(--color-text-secondary); line-height: 2.2; }
.modules-list a {
  color: var(--color-text-secondary);
  text-decoration: none;
  border-bottom: 0.5px solid var(--color-border);
  padding-bottom: 1px;
  transition: color 0.15s, border-color 0.15s;
}
.modules-list a:hover { color: var(--color-text-primary); border-color: var(--color-border-strong); }
.modules-list .coming {
  color: var(--color-text-muted);
  border-bottom: 0.5px dashed var(--color-border-strong);
  cursor: default;
  font-size: 15px;
}
.dot { margin: 0 10px; color: var(--color-border-strong); user-select: none; }

/* ─── BREADCRUMB ────────────────────────────────────────── */
.breadcrumb {
  padding: 1.5rem 0 0;
  font-size: 13px;
  color: var(--color-text-muted);
  display: flex;
  align-items: center;
  gap: 6px;
}
.breadcrumb a { color: var(--color-text-muted); text-decoration: none; }
.breadcrumb a:hover { color: var(--color-text-primary); }
.breadcrumb-sep { opacity: 0.5; }

/* ─── ARTICLE HEADER ────────────────────────────────────── */
.article-header {
  padding: 2.5rem 0;
  border-bottom: 0.5px solid var(--color-border);
  margin-bottom: 3rem;
}
.module-tag {
  display: inline-block;
  font-size: 12px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-weight: 500;
  padding: 4px 10px;
  border-radius: 4px;
  background: var(--beg-bg);
  color: var(--beg-text);
  margin-bottom: 1rem;
}
.article-title {
  font-family: var(--font-serif);
  font-size: clamp(32px, 5vw, 48px);
  font-weight: 700;
  color: var(--color-text-primary);
  line-height: 1.1;
  margin-bottom: 1rem;
  letter-spacing: -0.01em;
}
.article-title em { font-style: italic; font-weight: 400; }
.article-meta { display: flex; gap: 1.5rem; font-size: 14px; color: var(--color-text-muted); flex-wrap: wrap; }

/* ─── ARTICLE BODY ──────────────────────────────────────── */
.article-body h2 {
  font-family: var(--font-serif);
  font-size: 26px;
  font-weight: 400;
  color: var(--color-text-primary);
  margin: 3rem 0 1rem;
  line-height: 1.25;
}
.article-body h3 { font-size: 18px; font-weight: 500; color: var(--color-text-primary); margin: 2rem 0 0.6rem; }
.article-body p { color: var(--color-text-secondary); margin-bottom: 1.25rem; font-size: 17px; line-height: 1.75; }
.article-body ul, .article-body ol { color: var(--color-text-secondary); padding-left: 1.5rem; margin-bottom: 1.25rem; }
.article-body li { margin-bottom: 0.5rem; font-size: 17px; line-height: 1.7; }
.article-body strong { color: var(--color-text-primary); font-weight: 500; }

/* ─── CALLOUT BOX ───────────────────────────────────────── */
.callout {
  border-left: 3px solid var(--color-accent);
  background: var(--color-accent-bg);
  padding: 1.25rem 1.5rem;
  border-radius: 0 8px 8px 0;
  margin: 2rem 0;
}
.callout-label {
  font-size: 12px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-weight: 500;
  color: var(--color-accent);
  margin-bottom: 0.4rem;
}
.callout p { color: var(--color-text-secondary); margin: 0; font-size: 16px; }

/* ─── EXAMPLE BOX ───────────────────────────────────────── */
.example-box {
  border: 0.5px solid var(--color-border-strong);
  background: var(--color-surface);
  border-radius: 10px;
  padding: 1.5rem;
  margin: 2rem 0;
}
.example-label {
  font-size: 12px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-weight: 500;
  color: var(--color-text-muted);
  margin-bottom: 0.75rem;
}
.example-box p { margin: 0; font-size: 16px; color: var(--color-text-secondary); }

/* ─── COMPARE TABLE ─────────────────────────────────────── */
.compare-table { width: 100%; border-collapse: collapse; margin: 2rem 0; font-size: 15px; }
.compare-table th {
  text-align: left;
  padding: 10px 16px;
  background: var(--color-surface);
  border-bottom: 0.5px solid var(--color-border-strong);
  font-weight: 500;
  color: var(--color-text-primary);
  font-size: 14px;
}
.compare-table td { padding: 12px 16px; border-bottom: 0.5px solid var(--color-border); color: var(--color-text-secondary); vertical-align: top; }
.compare-table tr:last-child td { border-bottom: none; }

/* ─── KEY TERM ──────────────────────────────────────────── */
.key-term {
  display: grid;
  grid-template-columns: 180px 1fr;
  gap: 0;
  border: 0.5px solid var(--color-border);
  border-radius: 10px;
  overflow: hidden;
  margin: 1rem 0;
}
.key-term-word {
  background: var(--color-surface);
  padding: 1rem 1.25rem;
  font-family: var(--font-serif);
  font-size: 17px;
  color: var(--color-text-primary);
  border-right: 0.5px solid var(--color-border);
  display: flex;
  align-items: center;
}
.key-term-def { padding: 1rem 1.25rem; font-size: 15px; color: var(--color-text-secondary); line-height: 1.6; }

/* ─── TIMELINE ──────────────────────────────────────────── */
.timeline { margin: 2rem 0; }
.timeline-item {
  display: grid;
  grid-template-columns: 80px 1fr;
  gap: 1.5rem;
  padding-bottom: 2rem;
  position: relative;
}
.timeline-item::before {
  content: '';
  position: absolute;
  left: 39px;
  top: 28px;
  bottom: 0;
  width: 0.5px;
  background: var(--color-border-strong);
}
.timeline-item:last-child::before { display: none; }
.timeline-year { font-family: var(--font-serif); font-size: 15px; font-weight: 700; color: var(--color-accent); padding-top: 2px; text-align: right; }
.timeline-dot { width: 10px; height: 10px; background: var(--color-accent); border-radius: 50%; position: absolute; left: 35px; top: 7px; }
.timeline-content h3 { font-size: 16px; font-weight: 500; color: var(--color-text-primary); margin: 0 0 0.3rem; }
.timeline-content p { font-size: 15px; color: var(--color-text-secondary); margin: 0; line-height: 1.6; }

/* ─── SUMMARY BOX ───────────────────────────────────────── */
.summary-box {
  background: var(--color-surface);
  border: 0.5px solid var(--color-border-strong);
  border-radius: 12px;
  padding: 2rem;
  margin: 3rem 0;
}
.summary-box h3 { font-family: var(--font-serif); font-size: 20px; font-weight: 400; margin-bottom: 1rem; color: var(--color-text-primary); }
.summary-box ul { padding-left: 1.25rem; }
.summary-box li { font-size: 16px; color: var(--color-text-secondary); margin-bottom: 0.4rem; }

/* ─── CODE BLOCK ────────────────────────────────────────── */
.code-block {
  background: var(--color-surface);
  border: 0.5px solid var(--color-border-strong);
  border-radius: 8px;
  padding: 1.25rem 1.5rem;
  margin: 1.5rem 0;
  font-family: var(--font-mono);
  font-size: 14px;
  color: var(--color-text-secondary);
  line-height: 1.7;
  overflow-x: auto;
}
.code-comment { color: var(--color-text-muted); }

/* ─── MODULE CARD (category index pages) ───────────────── */
.module-card {
  display: grid;
  grid-template-columns: 48px 1fr auto;
  align-items: center;
  gap: 1.25rem;
  padding: 1.5rem;
  background: var(--color-surface);
  border: 0.5px solid var(--color-border);
  border-radius: 12px;
  text-decoration: none;
  margin-bottom: 1rem;
  transition: border-color 0.15s, box-shadow 0.15s;
}
.module-card:hover { border-color: var(--color-border-strong); box-shadow: 0 2px 12px rgba(30,80,160,0.07); }
.module-num { font-family: var(--font-serif); font-size: 28px; font-weight: 700; color: var(--color-border-strong); text-align: center; line-height: 1; }
.module-title { font-family: var(--font-serif); font-size: 20px; font-weight: 400; color: var(--color-text-primary); margin-bottom: 0.2rem; }
.module-desc { font-size: 14px; color: var(--color-text-muted); }
.module-meta { font-size: 13px; color: var(--color-text-muted); white-space: nowrap; text-align: right; }
.status-live { display: inline-block; font-size: 11px; padding: 2px 8px; border-radius: 10px; background: var(--beg-bg); color: var(--beg-text); font-weight: 500; margin-top: 4px; }

/* ─── ARTICLE NAV ───────────────────────────────────────── */
.article-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  margin-top: 4rem;
  padding-top: 2rem;
  border-top: 0.5px solid var(--color-border);
}
.article-nav a {
  display: block;
  padding: 1.25rem 1.5rem;
  background: var(--color-surface);
  border: 0.5px solid var(--color-border);
  border-radius: 10px;
  text-decoration: none;
  transition: border-color 0.15s;
}
.article-nav a:hover { border-color: var(--color-border-strong); }
.article-nav-label { font-size: 12px; letter-spacing: 0.08em; text-transform: uppercase; color: var(--color-text-muted); margin-bottom: 0.3rem; }
.article-nav-title { font-family: var(--font-serif); font-size: 17px; color: var(--color-text-primary); }
.article-nav .next { text-align: right; }
.article-nav .next-only { grid-column: 2; text-align: right; }

/* ─── FOOTER ────────────────────────────────────────────── */
footer {
  max-width: 900px;
  margin: 0 auto;
  padding: 2rem 2rem 3rem;
  border-top: 0.5px solid var(--color-border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}
.footer-left { font-size: 14px; color: var(--color-text-muted); }
.footer-left a { color: var(--color-text-muted); text-decoration: none; border-bottom: 0.5px solid var(--color-border); }
.footer-right a { font-size: 14px; color: var(--color-text-muted); text-decoration: none; }
.footer-right a:hover { color: var(--color-text-primary); }

/* ─── RESPONSIVE ────────────────────────────────────────── */
@media (max-width: 600px) {
  body { font-size: 16px; }
  main { padding: 0 1rem 4rem; }
  nav { padding: 0 1rem; }
  .level-row { grid-template-columns: 76px 1fr; }
  .level-col { padding: 1.5rem 1rem 1.5rem 0; }
  .cats-col { padding: 1.5rem 0 1.5rem 1rem; }
  .hero { padding: 3rem 0.5rem 2.5rem; }
  .hero-stats { gap: 1.5rem; }
  .hero-sub { font-size: 16px; }
  .key-term { grid-template-columns: 1fr; }
  .key-term-word { border-right: none; border-bottom: 0.5px solid var(--color-border); }
  .timeline-item { grid-template-columns: 60px 1fr; }
  .article-nav { grid-template-columns: 1fr; }
  .article-nav .next, .article-nav .next-only { text-align: left; grid-column: 1; }
  .module-card { grid-template-columns: 40px 1fr; }
  .module-meta { display: none; }
}