:root {
  --bg: #f9fafb;
  --card: #ffffff;
  --ink: #1e293b;
  --muted: #64748b;
  --accent: #06b6d4;
  --success: #10b981;
  --danger: #ef4444;
  --radius: 16px;
  --shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
  --transition: all 0.2s ease;
}

* { box-sizing: border-box; }
html, body {
  margin: 0;
  padding: 0;
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.6;
}

/* Header / Footer */
.app-header, .app-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 14px 20px;
  background: #ffffffcc;
  backdrop-filter: blur(8px);
  box-shadow: var(--shadow);
  position: sticky;
  top: 0;
  z-index: 10;
}
.app-footer {
  justify-content: center;
  font-size: 0.85rem;
  color: var(--muted);
  background: transparent;
  box-shadow: none;
}

h1, h2 {
  margin: 0 0 0.75rem;
  font-weight: 600;
}

main {
  max-width: 900px;
  margin: 20px auto;
  padding: 0 16px 80px;
}

/* Cards */
.card {
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 20px;
  transition: var(--transition);
}
.card:hover {
  transform: translateY(-2px);
}

/* Lists */
.card-list {
  display: grid;
  gap: 14px;
}

/* Buttons */
.btn {
  appearance: none;
  border: none;
  padding: 12px 20px;
  border-radius: var(--radius);
  cursor: pointer;
  font-weight: 500;
  transition: var(--transition);
}
.btn.primary {
  background: var(--accent);
  color: white;
}
.btn.primary:hover {
  background: #0891b2;
}
.btn.ghost {
  background: transparent;
  border: 1px solid #cbd5e1;
  color: var(--ink);
}
.btn.ghost:hover {
  background: #e2e8f0;
}
.btn[disabled] {
  opacity: 0.5;
  cursor: not-allowed;
}

/* Quiz */
.quiz-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 16px;
}
.choice {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 14px;
  border: 1px solid #e2e8f0;
  border-radius: var(--radius);
  background: #fff;
  cursor: pointer;
  transition: var(--transition);
}
.choice:hover {
  background: #f1f5f9;
}
.choice.correct {
  background: #ecfdf5;
  border-color: var(--success);
}
.choice.incorrect {
  background: #fef2f2;
  border-color: var(--danger);
}
.feedback {
  margin-top: 0.5rem;
  font-size: 0.95rem;
}
.correct { color: var(--success); }
.incorrect { color: var(--danger); }

/* Inputs */
input[type="text"] {
  width: 100%;
  padding: 0.7rem 1rem;
  border: 1px solid #cbd5e1;
  border-radius: var(--radius);
  background: white;
  color: var(--ink);
}

/* Misc */
.badge {
  background: var(--accent);
  color: white;
  border-radius: 999px;
  padding: 0.25rem 0.75rem;
  font-size: 0.75rem;
}
small, .muted { color: var(--muted); }