:root {
  --bg: #f5f5f7;
  --surface: #ffffff;
  --border: #e5e5ea;
  --text: #1d1d1f;
  --text-muted: #6e6e73;
  --accent-a: #6366f1;
  --accent-c: #f59e0b;
  --accent-r: #10b981;
  --ring: rgba(0, 0, 0, 0.06);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f0f12;
    --surface: #1a1a1e;
    --border: #2a2a2f;
    --text: #f2f2f4;
    --text-muted: #9a9aa2;
    --ring: rgba(255, 255, 255, 0.06);
  }
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Inter", "Segoe UI", Roboto, sans-serif;
  -webkit-font-smoothing: antialiased;
}

.page {
  max-width: 960px;
  margin: 0 auto;
  padding: 3.5rem 2rem 4rem;
}

.page-header {
  margin-bottom: 3rem;
}

.page-header h1 {
  margin: 0 0 0.5rem;
  font-size: 2.5rem;
  font-weight: 650;
  letter-spacing: -0.02em;
}

.subtitle {
  margin: 0;
  font-size: 1.05rem;
  color: var(--text-muted);
}

.theme {
  display: flex;
  flex-direction: column;
  gap: 1.75rem;
  padding: 2rem 2rem 2.25rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 20px;
  box-shadow: 0 1px 3px var(--ring);
}

.theme + .theme {
  margin-top: 4rem;
}

.theme-header {
  padding-bottom: 1.25rem;
  border-bottom: 1px solid var(--border);
}

.theme-title {
  margin: 0;
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.015em;
  color: var(--text);
}

.tracks {
  display: flex;
  flex-direction: column;
  gap: 2rem;
}

.track-label {
  margin: 0 0 0.75rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.85rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--accent);
}

.track-label::before {
  content: "";
  width: 6px;
  height: 6px;
  border-radius: 2px;
  background: var(--accent);
}

.track-label[data-accent="a"] { --accent: var(--accent-a); }
.track-label[data-accent="c"] { --accent: var(--accent-c); }
.track-label[data-accent="r"] { --accent: var(--accent-r); }

.track-pair,
.theme-cards {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.75rem;
}

@media (max-width: 640px) {
  .track-pair,
  .theme-cards {
    grid-template-columns: 1fr;
  }
  .page {
    padding: 3.5rem 1.25rem 3rem;
  }
  .theme {
    padding: 1.5rem 1.25rem 1.75rem;
  }
}

.card {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  padding: 1.75rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  text-decoration: none;
  color: inherit;
  overflow: hidden;
  transition: transform 0.18s ease, border-color 0.18s ease, box-shadow 0.18s ease;
  box-shadow: 0 1px 2px var(--ring);
}

.card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--accent);
  opacity: 0.9;
}

.card[data-accent="a"] { --accent: var(--accent-a); }
.card[data-accent="c"] { --accent: var(--accent-c); }
.card[data-accent="r"] { --accent: var(--accent-r); }

.card:hover {
  transform: translateY(-2px);
  border-color: var(--accent);
  box-shadow: 0 8px 20px var(--ring);
}

.card:active {
  transform: translateY(0);
}

.card-title {
  margin: 0;
  font-size: 1.15rem;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.card-desc {
  margin: 0;
  font-size: 0.92rem;
  color: var(--text-muted);
}

.card-arrow {
  position: absolute;
  bottom: 1.5rem;
  right: 1.75rem;
  font-size: 1.1rem;
  color: var(--accent);
  opacity: 0;
  transform: translateX(-4px);
  transition: opacity 0.18s ease, transform 0.18s ease;
}

.card:hover .card-arrow {
  opacity: 1;
  transform: translateX(0);
}