/* ============================================================
   Research Lab — institutional theme
   Palette: deep navy nav, near-black text, white/light-gray surfaces
   Typography: Inter (UI + body), IBM Plex Mono (code)
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=IBM+Plex+Mono:wght@400;500&display=swap');

:root {
  --nav-bg:      #0a2540;
  --nav-text:    #ffffff;
  --nav-muted:   #8daabe;
  --nav-hover:   #e8f0f7;
  --nav-active:  #c8ddf0;

  --body-bg:     #f7f8fb;
  --surface:     #ffffff;
  --surface-alt: #eef0f4;

  --text-primary:   #0c1a27;
  --text-secondary: #3a4f63;
  --text-muted:     #657889;

  --border:      #d2d8e0;
  --border-dark: #b0bbc7;
  --rule:        #e2e6ea;

  --link:        #0a4080;
  --link-hover:  #0a2540;
  --link-visited:#1a5a8a;

  --accent:      #0a4080;
  --accent-light:#dde9f5;

  --footer-bg:   #0a2540;
  --footer-text: #8daabe;
  --footer-rule: #1e3a56;

  --font-sans: 'Inter', system-ui, -apple-system, 'Segoe UI', sans-serif;
  --font-mono: 'IBM Plex Mono', 'Cascadia Code', ui-monospace, monospace;

  --max-w: 960px;
  --max-w-narrow: 720px;
}

/* ── Reset + Base ─────────────────────────────────────────── */

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

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.6;
  color: var(--text-primary);
  background: var(--body-bg);
}

/* ── Nav ──────────────────────────────────────────────────── */

.site-nav {
  background: var(--nav-bg);
  border-bottom: 1px solid #1e3a56;
}

.site-nav__inner {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 1.25rem;
  display: flex;
  align-items: center;
  gap: 0;
  min-height: 52px;
}

.site-nav__logo {
  font-weight: 700;
  font-size: .95rem;
  letter-spacing: .01em;
  color: var(--nav-text);
  text-decoration: none;
  white-space: nowrap;
  padding: .75rem 0;
  margin-right: 2rem;
}

.site-nav__logo:hover {
  color: var(--nav-hover);
}

.site-nav__links {
  display: flex;
  align-items: center;
  gap: 0;
  list-style: none;
  flex: 1;
}

.site-nav__links a {
  display: block;
  color: var(--nav-muted);
  text-decoration: none;
  font-size: .875rem;
  font-weight: 500;
  padding: .75rem .85rem;
  transition: color .15s;
  white-space: nowrap;
}

.site-nav__links a:hover {
  color: var(--nav-hover);
}

.site-nav__links a.active {
  color: var(--nav-active);
  border-bottom: 2px solid var(--nav-active);
}

/* ── Page header ──────────────────────────────────────────── */

.page-header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 2.5rem 1.25rem 2rem;
}

.page-header__inner {
  max-width: var(--max-w);
  margin: 0 auto;
}

.page-header__eyebrow {
  font-size: .75rem;
  font-weight: 600;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: .5rem;
}

.page-header h1 {
  font-size: 1.875rem;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.2;
  margin-bottom: .6rem;
}

.page-header__sub {
  font-size: 1rem;
  color: var(--text-secondary);
  max-width: 60ch;
  line-height: 1.5;
}

/* ── Main content wrapper ─────────────────────────────────── */

.page-content {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 2.5rem 1.25rem 4rem;
}

.page-content--narrow {
  max-width: var(--max-w-narrow);
}

/* ── Track cards (home page) ──────────────────────────────── */

.track-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1px;
  background: var(--border);
  border: 1px solid var(--border);
  margin: 2rem 0;
}

.track-card {
  background: var(--surface);
  padding: 1.5rem 1.5rem 1.75rem;
  text-decoration: none;
  color: inherit;
  display: block;
  transition: background .12s;
}

.track-card:hover {
  background: var(--accent-light);
}

.track-card__label {
  font-size: .7rem;
  font-weight: 600;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: .5rem;
}

.track-card__title {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: .5rem;
  line-height: 1.3;
}

.track-card:hover .track-card__title {
  color: var(--link-hover);
  text-decoration: underline;
}

.track-card__desc {
  font-size: .9rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

/* ── Track resource list ──────────────────────────────────── */

.resource-list {
  list-style: none;
  border: 1px solid var(--border);
  margin: 1.5rem 0;
}

.resource-list li {
  border-bottom: 1px solid var(--rule);
}

.resource-list li:last-child {
  border-bottom: none;
}

.resource-list a {
  display: flex;
  align-items: baseline;
  gap: .75rem;
  padding: 1rem 1.25rem;
  color: var(--link);
  text-decoration: none;
  font-weight: 500;
  transition: background .12s;
}

.resource-list a:hover {
  background: var(--accent-light);
  color: var(--link-hover);
  text-decoration: underline;
}

.resource-list__type {
  font-size: .7rem;
  font-weight: 600;
  letter-spacing: .07em;
  text-transform: uppercase;
  color: var(--text-muted);
  white-space: nowrap;
  min-width: 70px;
}

/* ── Prose (lit memos, panel notes) ──────────────────────── */

.prose {
  font-size: .975rem;
  line-height: 1.65;
  color: var(--text-primary);
}

.prose h2 {
  font-size: 1.2rem;
  font-weight: 700;
  margin: 2.5rem 0 .75rem;
  padding-bottom: .35rem;
  border-bottom: 1px solid var(--rule);
  color: var(--text-primary);
}

.prose h3 {
  font-size: 1rem;
  font-weight: 600;
  margin: 1.75rem 0 .4rem;
  color: var(--text-primary);
}

.prose p {
  margin: .75rem 0;
}

.prose ul, .prose ol {
  padding-left: 1.4rem;
  margin: .6rem 0 .6rem;
}

.prose li {
  margin: .35rem 0;
}

.prose strong {
  font-weight: 600;
}

.prose em {
  font-style: italic;
}

.prose a {
  color: var(--link);
  text-decoration: underline;
  text-underline-offset: 2px;
}

.prose a:hover {
  color: var(--link-hover);
}

.prose code {
  font-family: var(--font-mono);
  font-size: .875em;
  background: var(--surface-alt);
  border: 1px solid var(--border);
  padding: .1em .35em;
  border-radius: 2px;
  color: var(--text-primary);
}

.prose pre {
  background: #0f1a27;
  color: #c8d8e8;
  font-family: var(--font-mono);
  font-size: .875rem;
  padding: 1.1rem 1.25rem;
  overflow-x: auto;
  margin: 1rem 0;
  border: 1px solid #1e3a56;
}

.prose pre code {
  background: none;
  border: none;
  padding: 0;
  color: inherit;
  font-size: inherit;
}

.prose table {
  width: 100%;
  border-collapse: collapse;
  font-size: .9rem;
  margin: 1.25rem 0;
}

.prose th {
  background: var(--surface-alt);
  font-weight: 600;
  font-size: .8rem;
  letter-spacing: .03em;
  text-transform: uppercase;
  color: var(--text-secondary);
  padding: .5rem .75rem;
  border: 1px solid var(--border);
  text-align: left;
  vertical-align: top;
}

.prose td {
  padding: .5rem .75rem;
  border: 1px solid var(--border);
  vertical-align: top;
}

.prose blockquote {
  border-left: 3px solid var(--accent);
  padding: .5rem 1rem;
  margin: 1rem 0;
  color: var(--text-secondary);
  background: var(--accent-light);
}

.prose hr {
  border: none;
  border-top: 1px solid var(--rule);
  margin: 2rem 0;
}

/* ── Callout / notice ─────────────────────────────────────── */

.callout {
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  background: var(--accent-light);
  padding: .85rem 1rem;
  margin: 1.25rem 0;
  font-size: .9rem;
  color: var(--text-secondary);
}

.callout strong {
  color: var(--text-primary);
  font-weight: 600;
}

.callout.warn {
  border-left-color: #5a7a9a;
}

/* ── Breadcrumb ───────────────────────────────────────────── */

.breadcrumb {
  font-size: .8rem;
  color: var(--text-muted);
  margin-bottom: 1.5rem;
}

.breadcrumb a {
  color: var(--link);
  text-decoration: none;
}

.breadcrumb a:hover {
  text-decoration: underline;
}

.breadcrumb span {
  margin: 0 .4rem;
  color: var(--border-dark);
}

/* ── Section heading ──────────────────────────────────────── */

.section-heading {
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: .04em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin: 2.5rem 0 1rem;
  padding-bottom: .4rem;
  border-bottom: 1px solid var(--rule);
}

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

.site-footer {
  background: var(--footer-bg);
  color: var(--footer-text);
  border-top: 1px solid var(--footer-rule);
  padding: 2rem 1.25rem;
  margin-top: auto;
}

.site-footer__inner {
  max-width: var(--max-w);
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: .5rem;
}

.site-footer__disclaimer {
  font-size: .85rem;
  color: var(--footer-text);
  line-height: 1.5;
}

.site-footer__disclaimer strong {
  color: #c8d8e8;
  font-weight: 600;
}

.site-footer__links {
  display: flex;
  gap: 1.5rem;
  flex-wrap: wrap;
  font-size: .8rem;
  margin-top: .25rem;
}

.site-footer__links a {
  color: var(--nav-muted);
  text-decoration: none;
}

.site-footer__links a:hover {
  color: var(--nav-hover);
  text-decoration: underline;
}

/* ── Math display (inline TeX-style) ─────────────────────── */

.math-block {
  font-family: var(--font-mono);
  font-size: .9rem;
  background: var(--surface-alt);
  border: 1px solid var(--border);
  padding: .75rem 1rem;
  margin: .75rem 0;
  overflow-x: auto;
  color: var(--text-primary);
}

/* ── Badge / tag ──────────────────────────────────────────── */

.badge {
  display: inline-block;
  font-size: .7rem;
  font-weight: 600;
  letter-spacing: .07em;
  text-transform: uppercase;
  background: var(--surface-alt);
  border: 1px solid var(--border);
  color: var(--text-muted);
  padding: .15rem .5rem;
  margin-right: .35rem;
  vertical-align: middle;
}

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

@media (max-width: 640px) {
  .page-header h1 { font-size: 1.45rem; }
  .site-nav__links a { padding: .65rem .55rem; font-size: .8rem; }
  .site-nav__inner { flex-wrap: wrap; }
  .site-nav__links { flex-wrap: wrap; min-width: 0; }
  .track-grid { grid-template-columns: 1fr; }
}