/* Shared styles for /learn hub and sub-pages.
   Linked from learn.html and learn-*.html. Served via express.static with
   Cache-Control: no-cache (see server.js) so updates land without hard
   refresh — same convention as the HTML files. */

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
:root {
  --bg: #0f0f0f; --bg2: #161616; --surface: #1c1c1c; --border: #2a2a2a;
  --text: #f0f0f0; --text2: #a0a0a0; --text3: #707070; --text4: #505050;
  --accent: #E8FF47; --radius: 8px;
}
html { font-size: 17px; scroll-behavior: smooth; scroll-padding-top: 80px; }
body { font-family: 'Outfit', sans-serif; background: var(--bg); color: var(--text); line-height: 1.7; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
img { max-width: 100%; display: block; }

/* ── NAV ──────────────────────────────────────────────────────────────────── */
nav {
  display: flex; align-items: center; justify-content: space-between;
  padding: 0 32px; height: 60px;
  background: rgba(15,15,15,0.92); backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  position: sticky; top: 0; z-index: 100;
}
.nav-logo {
  display: flex; align-items: center; gap: 8px;
  font-weight: 800; font-size: 1.2rem; letter-spacing: -0.01em;
  color: var(--text);
}
.nav-logo:hover { text-decoration: none; }
.nav-logo img { width: 34px; height: 34px; border-radius: 50%; }
.nav-actions { display: flex; align-items: center; gap: 10px; }
.btn-ghost {
  background: none; border: 1px solid var(--border); color: var(--text2);
  padding: 6px 16px; border-radius: var(--radius);
  font-size: 0.85rem; font-weight: 500; cursor: pointer;
  font-family: inherit; transition: border-color 0.15s, color 0.15s;
}
.btn-ghost:hover { border-color: var(--text3); color: var(--text); text-decoration: none; }
.btn-accent {
  background: var(--accent); color: #0f0f0f; border: none;
  padding: 7px 18px; border-radius: var(--radius);
  font-size: 0.85rem; font-weight: 700; cursor: pointer;
  font-family: inherit; transition: opacity 0.15s;
}
.btn-accent:hover { opacity: 0.88; text-decoration: none; }

/* ── BREADCRUMB ───────────────────────────────────────────────────────────── */
.breadcrumb {
  max-width: 760px;
  margin: 0 auto;
  padding: 28px 32px 0;
  font-size: 0.82rem;
  color: var(--text3);
}
.breadcrumb a { color: var(--text3); }
.breadcrumb a:hover { color: var(--text2); text-decoration: none; }
.breadcrumb .sep { padding: 0 8px; color: var(--text4); }

/* ── CONTENT ──────────────────────────────────────────────────────────────── */
.content {
  max-width: 760px;
  margin: 0 auto;
  padding: 28px 32px 64px;
}
.eyebrow {
  font-size: 0.72rem; font-weight: 700; letter-spacing: 0.18em;
  text-transform: uppercase; color: var(--accent); margin-bottom: 12px;
}
.content h1 {
  font-size: 2.4rem; font-weight: 800; letter-spacing: -0.025em;
  line-height: 1.15; margin-bottom: 16px;
}
.content .lede {
  font-size: 1.05rem; color: var(--text2); line-height: 1.65;
  margin-bottom: 40px; max-width: 640px;
}

/* Section headings */
.content h2 {
  font-size: 1.55rem; font-weight: 800; letter-spacing: -0.02em;
  margin: 48px 0 16px; padding-top: 8px;
}
.content h3 {
  font-size: 1.2rem; font-weight: 700; letter-spacing: -0.01em;
  margin: 36px 0 12px; color: var(--text);
}
.content h4 {
  font-size: 1rem; font-weight: 700; margin: 28px 0 10px;
  color: var(--text);
}

/* Body text */
.content p { font-size: 0.95rem; color: var(--text2); margin-bottom: 16px; }
.content p strong, .content li strong { color: var(--text); font-weight: 600; }
.content em { color: var(--text); font-style: italic; }
.content ul, .content ol {
  font-size: 0.95rem; color: var(--text2);
  margin: 0 0 18px 24px;
}
.content ul li, .content ol li { margin-bottom: 8px; line-height: 1.65; }

/* Tables */
.table-wrap {
  margin: 22px 0 26px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: auto;
}
table {
  width: 100%; border-collapse: collapse;
  font-size: 0.9rem;
}
th, td {
  text-align: left; padding: 12px 16px;
  border-bottom: 1px solid var(--border);
  vertical-align: top;
}
th {
  font-weight: 700; font-size: 0.76rem; letter-spacing: 0.06em;
  text-transform: uppercase; color: var(--text3);
  background: var(--bg2);
}
td { color: var(--text2); }
td strong { color: var(--text); }
tr:last-child td { border-bottom: none; }

/* Callout / sidebar blocks */
.note {
  background: var(--bg2);
  border-left: 3px solid var(--accent);
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: 16px 22px;
  margin: 24px 0;
  font-size: 0.9rem;
  color: var(--text2);
}
.note strong { color: var(--text); }
.note .note-title {
  display: block; color: var(--text);
  font-weight: 700; font-size: 0.78rem;
  letter-spacing: 0.1em; text-transform: uppercase;
  margin-bottom: 8px;
}

/* Footnote superscripts */
sup.fn { font-size: 0.7rem; color: var(--accent); padding-left: 1px; }
sup.fn a { color: inherit; }

/* Sources block */
.sources {
  margin-top: 64px; padding-top: 32px;
  border-top: 1px solid var(--border);
}
.sources h2 {
  font-size: 1.1rem; font-weight: 700;
  margin: 0 0 16px;
}
.sources ol { padding-left: 22px; font-size: 0.86rem; color: var(--text2); }
.sources ol li { margin-bottom: 12px; line-height: 1.55; }
.sources ol li strong { color: var(--text); }

/* ── HUB-SPECIFIC: TOPIC CARDS ────────────────────────────────────────────── */
.topic-cards {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 8px 0 16px;
}
.topic-card {
  display: block;
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px 24px 22px;
  color: var(--text);
  transition: border-color 0.15s, transform 0.15s;
}
.topic-card:hover {
  border-color: var(--accent);
  text-decoration: none;
}
.topic-card .topic-num {
  font-size: 0.7rem; font-weight: 700; letter-spacing: 0.16em;
  color: var(--text4); margin-bottom: 10px;
  font-variant-numeric: tabular-nums;
}
.topic-card h2 {
  font-size: 1.15rem; font-weight: 800; letter-spacing: -0.01em;
  margin: 0 0 10px; line-height: 1.25;
  padding-top: 0; border-top: none;
}
.topic-card p {
  font-size: 0.88rem; color: var(--text2); line-height: 1.55;
  margin-bottom: 14px;
}
.topic-card .topic-read {
  display: inline-block; font-size: 0.82rem; font-weight: 600;
  color: var(--accent); transition: padding 0.15s;
}
.topic-card:hover .topic-read { padding-left: 4px; }

/* ── SUB-PAGE: PREV/NEXT NAVIGATION ───────────────────────────────────────── */
.prev-next {
  display: flex; gap: 12px;
  margin-top: 56px;
  border-top: 1px solid var(--border);
  padding-top: 28px;
}
.prev-next a {
  flex: 1;
  display: block;
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 18px;
  color: var(--text);
  transition: border-color 0.15s;
}
.prev-next a:hover {
  border-color: var(--accent);
  text-decoration: none;
}
.prev-next .pn-label {
  font-size: 0.7rem; font-weight: 700; letter-spacing: 0.12em;
  text-transform: uppercase; color: var(--text3);
  margin-bottom: 4px;
}
.prev-next .pn-title { font-size: 0.95rem; font-weight: 600; color: var(--text); }
.prev-next a.next { text-align: right; }

/* ── CTA AT END ───────────────────────────────────────────────────────────── */
.cta {
  margin-top: 48px;
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 28px;
  text-align: center;
}
.cta h3 { margin-top: 0; margin-bottom: 8px; font-size: 1.1rem; }
.cta p { font-size: 0.9rem; margin-bottom: 18px; }
.cta .btn-accent { display: inline-block; padding: 10px 24px; font-size: 0.9rem; }

/* ── FOOTER ───────────────────────────────────────────────────────────────── */
footer {
  border-top: 1px solid var(--border);
  padding: 28px 32px;
  font-size: 0.8rem; color: var(--text4); text-align: center;
}
footer a { color: var(--text4); }
footer a:hover { color: var(--text2); text-decoration: none; }

/* ── RESPONSIVE ───────────────────────────────────────────────────────────── */
@media (max-width: 600px) {
  nav { padding: 0 20px; }
  .breadcrumb, .content { padding-left: 20px; padding-right: 20px; }
  .content h1 { font-size: 1.8rem; }
  .content h2 { font-size: 1.3rem; }
  th, td { padding: 10px 12px; font-size: 0.84rem; }
  .topic-cards { grid-template-columns: 1fr; }
  .prev-next { flex-direction: column; }
  .prev-next a.next { text-align: left; }
}