:root {
  --bg: linear-gradient(160deg, #f8fafc 0%, #eef4ff 55%, #f5f9ff 100%);
  --ink: #0f172a;
  --muted: #475569;
  --surface: #ffffff;
  --surface-soft: #f8fbff;
  --line: #d9e4f5;
  --brand: #1d4ed8;
  --brand-strong: #1e3a8a;
  --shadow: 0 18px 34px -28px rgba(15, 23, 42, 0.55);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--bg);
  font: 500 16px/1.6 "Avenir Next", "Segoe UI", "Helvetica Neue", sans-serif;
}

a {
  color: inherit;
}

.site-shell {
  max-width: 1080px;
  margin: 0 auto;
  padding: 1rem;
}

.site-hero {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 20px;
  box-shadow: var(--shadow);
  padding: 1.3rem;
  margin-bottom: 1.1rem;
}

.site-eyebrow {
  margin: 0;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-size: 0.72rem;
  color: var(--muted);
}

.site-title {
  margin: 0.25rem 0 0;
  font-size: clamp(1.45rem, 3vw, 2rem);
  line-height: 1.14;
}

.site-subtitle {
  margin: 0.6rem 0 0;
  color: #334155;
  max-width: 68ch;
}

.site-actions {
  display: flex;
  gap: 0.65rem;
  flex-wrap: wrap;
  margin-top: 0.9rem;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.35rem;
  border-radius: 12px;
  border: 1px solid transparent;
  text-decoration: none;
  cursor: pointer;
  padding: 0.55rem 0.9rem;
  font: 600 0.9rem/1 "Avenir Next", "Segoe UI", "Helvetica Neue", sans-serif;
}

.button-primary {
  background: var(--brand-strong);
  color: #f8fafc;
}

.button-primary:hover {
  background: #172554;
}

.button-ghost {
  background: var(--surface);
  border-color: var(--line);
  color: var(--ink);
}

.button-ghost:hover {
  background: #f3f8ff;
}

.deck-directory-intro {
  background: rgba(255, 255, 255, 0.75);
  border: 1px solid var(--line);
  border-radius: 18px;
  padding: 1rem;
  margin-bottom: 0.9rem;
}

.deck-grid {
  display: grid;
  gap: 0.85rem;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
}

.deck-card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 0.95rem;
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
}

.deck-card h2,
.deck-card h3 {
  margin: 0;
  font-size: 1.08rem;
  line-height: 1.35;
}

.deck-card p {
  margin: 0;
  color: #334155;
}

.deck-meta {
  display: flex;
  gap: 0.45rem;
  flex-wrap: wrap;
  margin: 0;
  padding: 0;
  list-style: none;
}

.deck-meta li {
  display: inline-flex;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 0.22rem 0.58rem;
  background: var(--surface-soft);
  font-size: 0.74rem;
  color: #334155;
}

.deck-main {
  display: grid;
  gap: 0.95rem;
}

.breadcrumbs {
  margin: 0;
  font-size: 0.84rem;
  color: var(--muted);
}

.deck-summary {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 1rem;
}

.deck-summary h1 {
  margin: 0;
  font-size: clamp(1.35rem, 2.7vw, 2rem);
  line-height: 1.2;
}

.deck-summary p {
  margin: 0.65rem 0 0;
  color: #334155;
}

.deck-summary .button {
  margin-top: 0.8rem;
}

.deck-note {
  margin: 0.55rem 0 0;
  font-size: 0.84rem;
  color: var(--muted);
}

.flashcard-section {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 1rem;
}

.flashcard-section h2 {
  margin: 0;
  font-size: 1.2rem;
}

.flashcard-list {
  margin: 0.95rem 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 0.65rem;
}

.flashcard-item {
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--surface-soft);
  padding: 0.8rem;
}

.flashcard-label {
  margin: 0;
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: #475569;
}

.flashcard-front,
.flashcard-back {
  margin: 0.28rem 0 0;
  white-space: pre-wrap;
}

.flashcard-front {
  font-weight: 700;
  color: #0f172a;
}

.flashcard-back {
  color: #1e293b;
}

.site-footer {
  margin: 1.2rem 0 0.5rem;
  font-size: 0.84rem;
  color: var(--muted);
}

@media (max-width: 640px) {
  .site-shell {
    padding: 0.8rem;
  }

  .site-hero,
  .deck-directory-intro,
  .deck-summary,
  .flashcard-section,
  .deck-card {
    border-radius: 13px;
  }
}