:root {
  color-scheme: dark;
  background: #0d1117;
  color: #e6edf3;
  font-family: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  min-height: 100%;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 24px;
  background: radial-gradient(circle at top, rgba(58, 123, 213, 0.15), transparent 28%),
    radial-gradient(circle at bottom right, rgba(99, 102, 241, 0.15), transparent 32%);
}

a, a:visited, a:hover, a:active {
  text-decoration: none;
  color: inherit;
}

.app-shell {
  width: min(600px, 100%);
}

.card {
  background: rgba(15, 23, 42, 0.96);
  border: 1px solid rgba(148, 163, 184, 0.18);
  border-radius: 24px;
  box-shadow: 0 20px 60px rgba(8, 15, 28, 0.35);
  padding: 32px;
}

.hidden {
  display: none;
}

h1 {
  font-size: clamp(2rem, 3vw, 3rem);
  margin: 0 0 8px;
}

.subtitle {
  color: #94a3b8;
  margin: 0 0 28px;
  font-size: 1.05rem;
}

.button-grid {
  display: grid;
  gap: 16px;
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

button {
  border: none;
  border-radius: 14px;
  padding: 16px 20px;
  font-size: 1rem;
  cursor: pointer;
  transition: transform 0.15s ease, background 0.15s ease, box-shadow 0.15s ease;
  background: linear-gradient(135deg, #1f2937, #111827);
  color: #f8fafc;
  box-shadow: inset 0 0 0 1px rgba(148, 163, 184, 0.16);
}

button:hover {
  transform: translateY(-1px);
  box-shadow: 0 12px 24px rgba(15, 23, 42, 0.35);
}

button:disabled {
  opacity: 0.5;
  cursor: default;
  transform: none;
}

.quiz-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  margin-bottom: 24px;
  color: #cbd5e1;
}

.question-card {
  background: #111827;
  border: 1px solid rgba(148, 163, 184, 0.14);
  border-radius: 18px;
  padding: 24px;
  margin-bottom: 24px;
}

#question-text {
  margin: 0;
  font-size: 1.15rem;
  line-height: 1.6;
}

.answer-grid {
  display: grid;
  gap: 14px;
}

.answer-button {
  text-align: left;
  width: 100%;
  min-height: 56px;
  background: #111827;
  border: 1px solid rgba(148, 163, 184, 0.14);
  border-radius: 14px;
  padding: 16px;
  font-size: 1rem;
}

.answer-button:hover:not(:disabled) {
  background: #1f2937;
}

.answer-button.correct {
  border-color: #16a34a;
  background: rgba(22, 163, 74, 0.12);
}

.answer-button.incorrect {
  border-color: #dc2626;
  background: rgba(220, 38, 38, 0.12);
}

.feedback-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  margin-top: 20px;
}

#feedback {
  color: #e2e8f0;
  font-weight: 600;
}

.primary {
  background: #2563eb;
  color: white;
}

.primary:hover {
  background: #1d4ed8;
}

#final-score,
#final-percent {
  margin: 12px 0;
  font-size: 1.1rem;
  color: #cbd5e1;
}

@media (max-width: 520px) {
  .button-grid {
    grid-template-columns: 1fr;
  }
}