/* ============================================================
   B.Sc. CS Course Hub — design tokens
   Palette: aged paper + library-catalog ink & seal gold
   ============================================================ */

:root {
  --paper: #F6F1E5;
  --paper-alt: #EEE5D2;
  --ink: #1E2A38;
  --ink-soft: #4A5568;
  --gold: #A9812F;
  --line: #D9CDB0;
  --card-shadow: 0 1px 0 rgba(30, 42, 56, 0.06);

  --font-display: "Fraunces", "Iowan Old Style", serif;
  --font-body: "Inter", system-ui, -apple-system, sans-serif;
  --font-mono: "IBM Plex Mono", "SF Mono", monospace;

  --radius: 3px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font-body);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; }

/* ---------- Layout shell ---------- */

.shell {
  display: grid;
  grid-template-columns: 220px 1fr;
  min-height: 100vh;
}

@media (max-width: 800px) {
  .shell { grid-template-columns: 1fr; }
  .semnav { position: static; border-right: none; border-bottom: 1px solid var(--line); }
}

/* ---------- Semester nav (the "ledger tabs") ---------- */

.semnav {
  position: sticky;
  top: 0;
  align-self: start;
  height: 100vh;
  overflow-y: auto;
  border-right: 1px solid var(--line);
  background: var(--paper-alt);
  padding: 28px 0;
}

@media (max-width: 800px) {
  .semnav { height: auto; }
}

.semnav__brand {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 1.05rem;
  padding: 0 22px 20px;
  border-bottom: 1px solid var(--line);
  margin-bottom: 8px;
  letter-spacing: 0.01em;
}

.semnav__brand .college {
  display: block;
  font-family: var(--font-body);
  font-size: 0.72rem;
  font-weight: 500;
  color: var(--ink-soft);
  text-transform: none;
  letter-spacing: 0.01em;
  margin-top: 6px;
}

.semnav__brand span {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  font-weight: 400;
  color: var(--gold);
  text-transform: uppercase;
  letter-spacing: 0.12em;
  margin-top: 4px;
}

.semnav__list { list-style: none; margin: 0; padding: 0; }

.semnav__item a {
  display: flex;
  align-items: baseline;
  gap: 10px;
  text-decoration: none;
  padding: 9px 22px;
  color: var(--ink-soft);
  border-left: 3px solid transparent;
  font-size: 0.92rem;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}

.semnav__item a:hover {
  background: rgba(169, 129, 47, 0.08);
  color: var(--ink);
}

.semnav__item a.active {
  border-left-color: var(--gold);
  color: var(--ink);
  background: rgba(169, 129, 47, 0.1);
  font-weight: 600;
}

.semnav__num {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--gold);
  min-width: 1.4em;
}

/* ---------- Main content ---------- */

main { padding: 48px 56px 80px; max-width: 980px; }

@media (max-width: 800px) { main { padding: 32px 22px 60px; } }

.eyebrow {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--gold);
  margin: 0 0 10px;
}

h1.page-title {
  font-family: var(--font-display);
  font-size: 2.4rem;
  font-weight: 600;
  margin: 0 0 8px;
  letter-spacing: -0.01em;
}

.page-sub {
  color: var(--ink-soft);
  font-size: 1rem;
  margin: 0 0 40px;
  max-width: 60ch;
}

/* ---------- Home: semester grid ---------- */

.sem-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(210px, 1fr));
  gap: 18px;
  margin-top: 8px;
}

.sem-card {
  position: relative;
  display: block;
  text-decoration: none;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 22px 20px 20px;
  box-shadow: var(--card-shadow);
  transition: transform 0.15s ease, box-shadow 0.15s ease;
  overflow: hidden;
}

.sem-card::before {
  content: "";
  position: absolute;
  top: 0; left: 0;
  width: 100%;
  height: 4px;
  background: var(--gold);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.2s ease;
}

.sem-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 6px 16px rgba(30, 42, 56, 0.1);
}

.sem-card:hover::before { transform: scaleX(1); }

.sem-card__num {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--gold);
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.sem-card__title {
  font-family: var(--font-display);
  font-size: 1.35rem;
  font-weight: 600;
  margin: 6px 0 4px;
}

.sem-card__meta {
  font-size: 0.82rem;
  color: var(--ink-soft);
}

/* ---------- Subject "index card" tiles ---------- */

.subject-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
  gap: 16px;
}

.subject-card {
  position: relative;
  text-decoration: none;
  display: block;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 18px 16px;
  box-shadow: var(--card-shadow);
  transition: box-shadow 0.15s ease, transform 0.15s ease;
}

.subject-card:hover {
  box-shadow: 0 6px 16px rgba(30, 42, 56, 0.1);
  transform: translateY(-2px);
}

/* die-cut catalog tab */
.subject-card__tab {
  position: absolute;
  top: -1px; left: 18px;
  background: var(--ink);
  color: var(--paper);
  font-family: var(--font-mono);
  font-size: 0.65rem;
  letter-spacing: 0.06em;
  padding: 3px 8px;
  border-radius: 0 0 3px 3px;
}

.subject-card__title {
  font-family: var(--font-display);
  font-size: 1.12rem;
  font-weight: 600;
  margin: 14px 0 6px;
}

.subject-card__meta {
  font-size: 0.8rem;
  color: var(--ink-soft);
  font-family: var(--font-mono);
}

/* ---------- Subject detail: category tabs ---------- */

.tabbar {
  display: flex;
  gap: 4px;
  border-bottom: 1px solid var(--line);
  margin-bottom: 24px;
  flex-wrap: wrap;
}

.tabbar button {
  font-family: var(--font-body);
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--ink-soft);
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  padding: 10px 4px;
  margin-right: 22px;
  cursor: pointer;
  transition: color 0.15s, border-color 0.15s;
}

.tabbar button:hover { color: var(--ink); }

.tabbar button.active {
  color: var(--ink);
  border-bottom-color: var(--gold);
}

.filelist { list-style: none; margin: 0; padding: 0; }

.filelist__item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 13px 16px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  margin-bottom: 8px;
  background: #fff;
  transition: border-color 0.15s;
}

.filelist__item:hover { border-color: var(--gold); }

.filelist__name {
  font-size: 0.94rem;
  font-weight: 500;
}

.filelist__tag {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  color: var(--ink-soft);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.filelist__link {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  text-decoration: none;
  color: var(--gold);
  border: 1px solid var(--gold);
  padding: 5px 10px;
  border-radius: 2px;
  white-space: nowrap;
  transition: background 0.15s, color 0.15s;
}

.filelist__link:hover { background: var(--gold); color: #fff; }

.empty-state {
  border: 1px dashed var(--line);
  border-radius: var(--radius);
  padding: 30px 24px;
  color: var(--ink-soft);
  font-size: 0.92rem;
  text-align: center;
}

.empty-state code {
  font-family: var(--font-mono);
  background: var(--paper-alt);
  padding: 2px 6px;
  border-radius: 2px;
}

.back-link {
  display: inline-block;
  margin-bottom: 18px;
  font-size: 0.85rem;
  color: var(--ink-soft);
  text-decoration: none;
  font-family: var(--font-mono);
}

.back-link:hover { color: var(--gold); }

.breadcrumb {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--ink-soft);
  margin-bottom: 6px;
}

.breadcrumb .sep { margin: 0 6px; color: var(--line); }

.tabbar button .tab-count {
  display: inline-block;
  min-width: 1.4em;
  margin-left: .35rem;
  padding: .08rem .35rem;
  border-radius: 999px;
  background: rgba(0,0,0,.08);
  font-size: .78em;
}