:root {
  color-scheme: dark;
  font-family: Inter, system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
}

body {
  margin: 0;
  min-height: 100vh;
  display: grid;
  place-items: center;
  background: radial-gradient(circle at top, #1f3a5f, #0d1321 60%);
  color: #f3f4f6;
}

.app {
  width: min(900px, 92vw);
  padding: 1.5rem;
}

h1, h2 { margin: 0 0 0.75rem; }
.subtitle { margin: 0 0 1.5rem; color: #cbd5e1; }

.card, .quiz {
  background: rgba(15, 23, 42, 0.85);
  border: 1px solid rgba(148, 163, 184, 0.25);
  border-radius: 16px;
  padding: 1.2rem;
  box-shadow: 0 12px 30px rgba(0,0,0,.25);
}

.letter, .quiz-letter {
  font-size: clamp(3rem, 8vw, 5.5rem);
  font-weight: 700;
  text-align: center;
  margin-bottom: 0.8rem;
}

.meta p { margin: 0.35rem 0; }

.controls {
  margin: 1rem 0 1.4rem;
  display: flex;
  gap: 0.6rem;
  flex-wrap: wrap;
}

button {
  border: 0;
  border-radius: 10px;
  padding: 0.65rem 1rem;
  cursor: pointer;
  font-weight: 600;
  background: #2563eb;
  color: white;
}

button:hover { filter: brightness(1.08); }
button.secondary { background: #334155; }

#quizForm {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

input {
  flex: 1;
  min-width: 220px;
  border: 1px solid #475569;
  background: #0f172a;
  color: #e2e8f0;
  border-radius: 10px;
  padding: 0.65rem 0.75rem;
}

.result { min-height: 1.4rem; font-weight: 600; }
.result.ok { color: #4ade80; }
.result.bad { color: #fca5a5; }