:root {
  --bg: #fbfaf6;
  --bg-muted: #f3f1ea;
  --text: #1c1917;
  --text-muted: #57534e;
  --text-faint: #a8a29e;
  --border: #e7e5e0;
  --accent: #1e3a5f;       /* deep navy */
  --accent-soft: #3b5b86;
  --accent-warm: #7a2e2e;  /* burgundy */
  --accent-olive: #4a5d3a; /* sage/olive */
}

html, body {
  background: var(--bg);
  color: var(--text);
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Helvetica Neue', sans-serif;
  font-feature-settings: "kern", "liga";
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

h1, h2, h3, h4, .serif {
  font-family: 'Crimson Pro', 'EB Garamond', Georgia, serif;
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--text);
}

h1 { font-weight: 700; letter-spacing: -0.02em; }

.font-mono {
  font-family: 'JetBrains Mono', ui-monospace, 'SF Mono', monospace;
  font-variant-numeric: tabular-nums;
}

.text-accent { color: var(--accent); }
.text-accent-warm { color: var(--accent-warm); }
.text-accent-olive { color: var(--accent-olive); }
.text-muted { color: var(--text-muted); }
.text-faint { color: var(--text-faint); }

.bg-paper { background: var(--bg); }
.bg-muted { background: var(--bg-muted); }
.border-subtle { border-color: var(--border); }

a { color: var(--accent); text-decoration: none; transition: color 0.15s ease; }
a:hover { color: var(--accent-warm); }

.link-underline { text-decoration: underline; text-decoration-color: rgba(30,58,95,0.3); text-underline-offset: 3px; }
.link-underline:hover { text-decoration-color: var(--accent-warm); }

/* Subtle paper texture */
.paper-bg {
  background-color: var(--bg);
  background-image:
    radial-gradient(circle at 20% 10%, rgba(30,58,95,0.025), transparent 40%),
    radial-gradient(circle at 80% 90%, rgba(122,46,46,0.02), transparent 40%);
}

::selection {
  background: rgba(30,58,95,0.15);
  color: var(--text);
}

::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: #d6d3cd; border-radius: 5px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-faint); }

/* Article spacing */
article + article { margin-top: 1.5rem; }

/* Realistic book-cover thumbnail — matches the "Modern Business Analytics"
   navy + gold serif design used across the three Spring-2026 textbooks. */
.bk {
  flex-shrink: 0;
  width: 132px;
  height: 184px;
  padding: 10px 8px 8px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  text-align: center;
  color: #fdfcf7;
  text-decoration: none;
  border-radius: 1px 4px 4px 1px;
  box-shadow:
    2px 3px 8px rgba(0,0,0,0.22),
    inset 3px 0 0 rgba(255,255,255,0.10),
    inset -1px 0 0 rgba(0,0,0,0.18);
  background: #0d1f3a; /* default deep navy — overridden per book */
  transition: transform 0.18s ease, box-shadow 0.18s ease;
}
.bk:hover {
  transform: translateY(-3px) rotate(-0.6deg);
  color: #fdfcf7;
  box-shadow:
    3px 6px 14px rgba(0,0,0,0.30),
    inset 3px 0 0 rgba(255,255,255,0.12),
    inset -1px 0 0 rgba(0,0,0,0.20);
}
.bk-rule {
  width: 30px;
  height: 1.5px;
  background: #d4a017;
  margin: 0 auto 6px;
}
.bk-bot .bk-rule { margin: 6px auto 0; }
.bk-cat {
  font-family: 'Inter', sans-serif;
  font-size: 6px;
  font-weight: 600;
  letter-spacing: 0.18em;
  color: #d4a017;
  text-transform: uppercase;
}
.bk-title {
  font-family: 'Crimson Pro', Georgia, serif;
  font-weight: 700;
  font-size: 17px;
  line-height: 1.02;
  letter-spacing: -0.01em;
  padding: 0 2px;
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 4px 0;
}
.bk-author {
  font-family: 'Inter', sans-serif;
  font-size: 8px;
  font-weight: 700;
  letter-spacing: 0.18em;
}
.bk-sub {
  font-family: 'Inter', sans-serif;
  font-size: 5.5px;
  font-weight: 500;
  letter-spacing: 0.10em;
  color: rgba(212,160,23,0.85);
  margin-top: 3px;
  text-transform: uppercase;
}

/* Color variants — same template, different cover stocks */
.bk-navy     { background: #0d1f3a; }
.bk-burgundy { background: #3a1414; }
.bk-forest   { background: #14352a; }
.bk-black    { background: #0a0a0b; }
.bk-black .bk-rule { background: #c41e1e; }
.bk-black .bk-cat  { color: #c41e1e; }
.bk-black .bk-sub  { color: rgba(196,30,30,0.88); }

.textbook-card {
  display: flex;
  align-items: flex-start;
  gap: 1rem;
  padding: 1rem;
  background: var(--bg-muted);
  border-radius: 4px;
  margin-top: 0.75rem;
}
.textbook-card ol { margin: 0; padding: 0; list-style: none; }
.textbook-card ol li {
  font-size: 0.83rem;
  color: var(--text-muted);
  padding: 1px 0;
}
.textbook-card ol li::before {
  content: counter(toc) ".";
  counter-increment: toc;
  font-family: 'JetBrains Mono', monospace;
  color: var(--text-faint);
  margin-right: 0.5rem;
  font-size: 0.75rem;
}
.textbook-card ol { counter-reset: toc; }

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; animation: none !important; }
}