/* ───────────────────────────────────────────────
   University Coursework — Polished Card Layout
   Dark mode · Gradient header · CSS counters
   No external dependencies
   ─────────────────────────────────────────────── */

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

:root {
  --accent: #2563eb;
  --accent-soft: rgba(37, 99, 235, 0.08);
  --bg: #f8fafc;
  --card-bg: #ffffff;
  --text: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --border: #e2e8f0;
  --radius: 14px;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
  --shadow-hover: 0 12px 28px rgba(37, 99, 235, 0.13), 0 4px 10px rgba(0, 0, 0, 0.04);
  --ease: cubic-bezier(0.4, 0, 0.2, 1);
  --header-from: #1e3a5f;
  --header-to: #2563eb;
  --counter-color: rgba(37, 99, 235, 0.07);
  --arrow-color: var(--text-muted);
}

@media (prefers-color-scheme: dark) {
  :root {
    --accent: #60a5fa;
    --accent-soft: rgba(96, 165, 250, 0.08);
    --bg: #0b1120;
    --card-bg: #162032;
    --text: #e2e8f0;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --border: #1e3050;
    --shadow: 0 1px 4px rgba(0, 0, 0, 0.3);
    --shadow-hover: 0 12px 28px rgba(96, 165, 250, 0.1), 0 4px 10px rgba(0, 0, 0, 0.3);
    --header-from: #0b1120;
    --header-to: #1e40af;
    --counter-color: rgba(96, 165, 250, 0.06);
    --arrow-color: var(--text-muted);
  }
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter,
    Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

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

.site-header {
  background: linear-gradient(135deg, var(--header-from), var(--header-to));
  padding: 3.2rem 2rem 2.6rem;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.site-header::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse at 25% 40%, rgba(255, 255, 255, 0.07) 0%, transparent 60%),
    radial-gradient(ellipse at 75% 60%, rgba(255, 255, 255, 0.04) 0%, transparent 50%);
  pointer-events: none;
}

.site-header h1 {
  font-size: 1.85rem;
  font-weight: 700;
  color: #ffffff;
  letter-spacing: -0.02em;
  position: relative;
}

.site-header .subtitle {
  margin-top: 0.5rem;
  font-size: 0.92rem;
  color: rgba(255, 255, 255, 0.7);
  font-weight: 400;
  position: relative;
}

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

.content {
  max-width: 1100px;
  width: 100%;
  margin: 2.5rem auto;
  padding: 0 1.5rem;
  flex: 1;
}

/* ── Card grid ───────────────────────────────── */

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.25rem;
  list-style: none;
  counter-reset: card-counter;
}

.card {
  counter-increment: card-counter;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  transition:
    box-shadow 0.3s var(--ease),
    transform 0.3s var(--ease),
    border-color 0.3s var(--ease);
  position: relative;
  overflow: hidden;
}

.card:hover {
  box-shadow: var(--shadow-hover);
  transform: translateY(-4px);
  border-color: var(--accent);
}

/* faint large number watermark */
.card::before {
  content: counter(card-counter, decimal-leading-zero);
  position: absolute;
  top: -0.15rem;
  right: 0.8rem;
  font-size: 3.8rem;
  font-weight: 800;
  color: var(--counter-color);
  line-height: 1;
  pointer-events: none;
  transition: color 0.3s var(--ease);
}

.card:hover::before {
  color: var(--accent-soft);
}

/* link fills the whole card */
.card a {
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 1.6rem 1.6rem 1.6rem 1.5rem;
  text-decoration: none;
  color: inherit;
  min-height: 120px;
  position: relative;
}

.card .card-title {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 0.4rem;
  transition: color 0.3s var(--ease);
}

.card:hover .card-title {
  color: var(--accent);
}

.card .card-desc {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.55;
}

/* arrow indicator */
.card a::after {
  content: "\2192";
  position: absolute;
  right: 1.3rem;
  top: 50%;
  transform: translateY(-50%) translateX(-4px);
  font-size: 1.15rem;
  color: var(--arrow-color);
  opacity: 0;
  transition:
    opacity 0.25s var(--ease),
    transform 0.25s var(--ease),
    color 0.25s var(--ease);
}

.card:hover a::after {
  opacity: 1;
  transform: translateY(-50%) translateX(0);
  color: var(--accent);
}

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

.site-footer {
  text-align: center;
  padding: 2rem 1rem;
  font-size: 0.82rem;
  color: var(--text-muted);
  margin-top: auto;
}

.site-footer a {
  color: var(--accent);
  text-decoration: none;
  font-weight: 500;
  transition: opacity 0.2s;
}

.site-footer a:hover {
  text-decoration: underline;
  opacity: 0.85;
}

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

@media (max-width: 640px) {
  .site-header {
    padding: 2.2rem 1rem 1.8rem;
  }

  .site-header h1 {
    font-size: 1.35rem;
  }

  .card-grid {
    grid-template-columns: 1fr;
  }

  .content {
    padding: 0 0.75rem;
    margin: 1.5rem auto;
  }

  .card::before {
    font-size: 2.8rem;
  }
}