/* ═══════════════════════════════════════════════════════════════
   FP Capstone — One Propagator, Three Regimes
   Academic site stylesheet
   ═══════════════════════════════════════════════════════════════ */

@import url('https://fonts.googleapis.com/css2?family=Source+Serif+4:ital,opsz,wght@0,8..60,300;0,8..60,400;0,8..60,600;0,8..60,700;1,8..60,300;1,8..60,400&family=JetBrains+Mono:wght@400;500&family=Source+Sans+3:ital,wght@0,300;0,400;0,600;0,700;1,400&display=swap');

:root {
  --ink: #1a1a2e;
  --ink-light: #3a3a5e;
  --ink-muted: #6b6b8d;
  --bg: #faf9f7;
  --bg-warm: #f4f1ec;
  --bg-code: #f0ede6;
  --accent: #8b2500;
  --accent-light: #c44d2a;
  --border: #d4d0c8;
  --border-light: #e8e4dc;
  --nav-bg: #1a1a2e;
  --nav-text: #d4d0c8;
  --nav-active: #faf9f7;
  --table-header: #2a2a4e;
  --table-alt: #f4f1ec;
  --guardian: #6b3a2e;
  --guardian-bg: #fdf6f0;
  --guardian-border: #d4a68c;
  --note-bg: #f0f4f8;
  --note-border: #8ca8c4;
  --max-w: 52rem;
}

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

html { font-size: 17px; scroll-behavior: smooth; }

body {
  font-family: 'Source Serif 4', Georgia, 'Times New Roman', serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

/* ── Navigation ──────────────────────────────────────────────── */

nav {
  background: var(--nav-bg);
  border-bottom: 3px solid var(--accent);
  position: sticky;
  top: 0;
  z-index: 100;
}

nav .nav-inner {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 2rem;
  display: flex;
  align-items: stretch;
  gap: 0;
}

nav .nav-home {
  font-family: 'Source Sans 3', sans-serif;
  font-weight: 600;
  font-size: 0.82rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--nav-text);
  text-decoration: none;
  padding: 0.9rem 1.2rem 0.9rem 0;
  border-right: 1px solid rgba(255,255,255,0.1);
  display: flex;
  align-items: center;
  transition: color 0.2s;
  white-space: nowrap;
}

nav .nav-home:hover { color: var(--nav-active); }

nav .nav-links {
  display: flex;
  list-style: none;
  gap: 0;
  overflow-x: auto;
}

nav .nav-links a {
  font-family: 'Source Sans 3', sans-serif;
  font-size: 0.82rem;
  font-weight: 400;
  letter-spacing: 0.03em;
  color: var(--nav-text);
  text-decoration: none;
  padding: 0.9rem 1rem;
  display: block;
  border-bottom: 2px solid transparent;
  transition: color 0.2s, border-color 0.2s;
  white-space: nowrap;
}

nav .nav-links a:hover {
  color: var(--nav-active);
  border-bottom-color: rgba(255,255,255,0.3);
}

nav .nav-links a.active {
  color: var(--nav-active);
  border-bottom-color: var(--accent-light);
  font-weight: 600;
}

/* ── Main Content ────────────────────────────────────────────── */

main {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 2.5rem 2rem 4rem;
}

/* ── Typography ──────────────────────────────────────────────── */

h1 {
  font-family: 'Source Serif 4', Georgia, serif;
  font-size: 2.2rem;
  font-weight: 700;
  color: var(--ink);
  line-height: 1.2;
  margin-bottom: 0.3rem;
}

h1 .subtitle {
  display: block;
  font-size: 1.1rem;
  font-weight: 300;
  color: var(--ink-muted);
  margin-top: 0.4rem;
  line-height: 1.5;
}

h2 {
  font-family: 'Source Serif 4', Georgia, serif;
  font-size: 1.45rem;
  font-weight: 600;
  color: var(--ink);
  margin-top: 2.5rem;
  margin-bottom: 0.8rem;
  padding-bottom: 0.3rem;
  border-bottom: 1px solid var(--border-light);
}

h3 {
  font-family: 'Source Sans 3', sans-serif;
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--ink-light);
  margin-top: 1.8rem;
  margin-bottom: 0.6rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

p { margin-bottom: 1rem; }

a { color: var(--accent); text-decoration: none; border-bottom: 1px solid transparent; transition: border-color 0.2s; }
a:hover { border-bottom-color: var(--accent); }

strong { font-weight: 600; }
em { font-style: italic; }

/* ── Header block ────────────────────────────────────────────── */

.page-header {
  margin-bottom: 2rem;
  padding-bottom: 1.5rem;
  border-bottom: 2px solid var(--border);
}

.page-header .meta {
  font-family: 'Source Sans 3', sans-serif;
  font-size: 0.82rem;
  color: var(--ink-muted);
  margin-top: 0.8rem;
  line-height: 1.6;
}

.page-header .meta span {
  display: inline-block;
  margin-right: 1.5rem;
}

.endorsement {
  font-family: 'Source Sans 3', sans-serif;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  color: var(--ink-muted);
  background: var(--bg-warm);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 0.3rem 0.7rem;
  display: inline-block;
  margin-top: 0.6rem;
}

/* ── Equations ────────────────────────────────────────────────── */

.equation {
  font-family: 'JetBrains Mono', 'Courier New', monospace;
  font-size: 1.05rem;
  text-align: center;
  padding: 1.2rem 1.5rem;
  margin: 1.5rem 0;
  background: var(--bg-warm);
  border-left: 3px solid var(--accent);
  border-radius: 0 3px 3px 0;
  overflow-x: auto;
}

/* ── Tables ───────────────────────────────────────────────────── */

table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.2rem 0 1.5rem;
  font-size: 0.92rem;
  line-height: 1.5;
}

thead th {
  font-family: 'Source Sans 3', sans-serif;
  font-weight: 600;
  font-size: 0.82rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  background: var(--table-header);
  color: #fff;
  padding: 0.65rem 0.8rem;
  text-align: left;
}

tbody td {
  padding: 0.6rem 0.8rem;
  border-bottom: 1px solid var(--border-light);
  vertical-align: top;
}

tbody tr:nth-child(even) { background: var(--table-alt); }

/* ── Lists ────────────────────────────────────────────────────── */

ol, ul {
  margin: 0.8rem 0 1.2rem 1.5rem;
}

li {
  margin-bottom: 0.4rem;
  padding-left: 0.3rem;
}

ol ol, ul ul { margin-top: 0.3rem; margin-bottom: 0.3rem; }

/* ── Boxes ────────────────────────────────────────────────────── */

.box {
  padding: 1rem 1.3rem;
  margin: 1.5rem 0;
  border-radius: 3px;
  font-size: 0.95rem;
}

.box-guardian {
  background: var(--guardian-bg);
  border-left: 3px solid var(--guardian-border);
}

.box-guardian .box-label {
  font-family: 'Source Sans 3', sans-serif;
  font-weight: 700;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--guardian);
  margin-bottom: 0.4rem;
}

.box-note {
  background: var(--note-bg);
  border-left: 3px solid var(--note-border);
}

.box-note .box-label {
  font-family: 'Source Sans 3', sans-serif;
  font-weight: 700;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: #3a6a8a;
  margin-bottom: 0.4rem;
}

.box-deliverable {
  background: #f8f5f0;
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
}

.box-deliverable .box-label {
  font-family: 'Source Sans 3', sans-serif;
  font-weight: 700;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--accent);
  margin-bottom: 0.4rem;
}

/* ── Cards (landing page) ────────────────────────────────────── */

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(16rem, 1fr));
  gap: 1.2rem;
  margin: 1.5rem 0;
}

.card {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1.3rem 1.4rem;
  transition: border-color 0.2s, box-shadow 0.2s;
  text-decoration: none;
  color: var(--ink);
  display: block;
}

.card:hover {
  border-color: var(--accent);
  box-shadow: 0 2px 12px rgba(26,26,46,0.08);
}

.card .card-label {
  font-family: 'Source Sans 3', sans-serif;
  font-weight: 600;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--ink-muted);
  margin-bottom: 0.4rem;
}

.card .card-title {
  font-family: 'Source Serif 4', Georgia, serif;
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--ink);
  margin-bottom: 0.4rem;
  line-height: 1.3;
}

.card .card-desc {
  font-size: 0.88rem;
  color: var(--ink-muted);
  line-height: 1.5;
}

/* ── Repo link ────────────────────────────────────────────────── */

.repo-link {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.85rem;
  background: var(--bg-code);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 0.6rem 1rem;
  display: inline-block;
  margin: 0.5rem 0;
}

/* ── Footer ───────────────────────────────────────────────────── */

footer {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 1.5rem 2rem;
  border-top: 1px solid var(--border);
  font-family: 'Source Sans 3', sans-serif;
  font-size: 0.78rem;
  color: var(--ink-muted);
  line-height: 1.6;
}

footer a { color: var(--ink-muted); }
footer a:hover { color: var(--accent); }

/* ── Responsive ──────────────────────────────────────────────── */

@media (max-width: 640px) {
  html { font-size: 16px; }
  nav .nav-inner { padding: 0 1rem; }
  nav .nav-home { padding: 0.7rem 0.8rem 0.7rem 0; font-size: 0.75rem; }
  nav .nav-links a { padding: 0.7rem 0.7rem; font-size: 0.75rem; }
  main { padding: 1.5rem 1rem 3rem; }
  h1 { font-size: 1.7rem; }
  .cards { grid-template-columns: 1fr; }
}