:root {
  --color-bg: #f8fafc;
  --color-surface: #ffffff;
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-success: #16a34a;
  --color-error: #dc2626;
  --color-text: #1e293b;
  --color-text-muted: #64748b;
  --color-border: #e2e8f0;
  --radius: 12px;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: system-ui, -apple-system, sans-serif;
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 1rem;
}

.game-container {
  width: 100%;
  max-width: 480px;
}

.game-header {
  text-align: center;
  margin-bottom: 1.5rem;
}

.game-header h1 {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--color-primary);
}

.game-footer {
  text-align: center;
  margin-top: 2rem;
  color: var(--color-text-muted);
  font-size: 0.875rem;
}

.screen {
  display: none;
}

.screen.active {
  display: block;
}

.card {
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: 2rem;
  box-shadow: var(--shadow);
  text-align: center;
}

.icon-large {
  font-size: 4rem;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 1rem;
}

h2 {
  font-size: 1.5rem;
  margin-bottom: 1rem;
  color: var(--color-text);
}

.instructions {
  color: var(--color-text-muted);
  margin-bottom: 1.5rem;
}

.instructions strong {
  color: var(--color-text);
}

.btn-primary {
  background: var(--color-primary);
  color: white;
  border: none;
  padding: 0.875rem 2rem;
  font-size: 1rem;
  font-weight: 600;
  border-radius: var(--radius);
  cursor: pointer;
  transition: background 0.2s;
}

.btn-primary:hover {
  background: var(--color-primary-dark);
}

.btn-primary:active {
  transform: scale(0.98);
}

.progress-bar {
  margin-bottom: 1rem;
  position: relative;
}

#question-counter {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin-bottom: 0.5rem;
  display: block;
}

.progress-fill {
  height: 6px;
  background: var(--color-border);
  border-radius: 3px;
  overflow: hidden;
}

.progress-fill::after {
  content: '';
  display: block;
  height: 100%;
  background: var(--color-primary);
  width: var(--progress, 0%);
  transition: width 0.3s;
}

.question-card {
  padding: 2.5rem 2rem;
}

.question {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 2rem;
}

.options {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.75rem;
  margin-bottom: 1.5rem;
}

.option-btn {
  background: var(--color-surface);
  border: 2px solid var(--color-border);
  padding: 1rem;
  font-size: 1.25rem;
  font-weight: 600;
  border-radius: var(--radius);
  cursor: pointer;
  transition: all 0.2s;
}

.option-btn:hover {
  border-color: var(--color-primary);
}

.option-btn.correct {
  background: var(--color-success);
  border-color: var(--color-success);
  color: white;
}

.option-btn.wrong {
  background: var(--color-error);
  border-color: var(--color-error);
  color: white;
}

.option-btn:disabled {
  cursor: default;
  opacity: 0.7;
}

.feedback {
  min-height: 1.5rem;
  font-weight: 600;
  font-size: 1rem;
}

.feedback.correct {
  color: var(--color-success);
}

.feedback.wrong {
  color: var(--color-error);
}

.score-display {
  margin-bottom: 1.5rem;
}

.score-number {
  font-size: 4rem;
  font-weight: 700;
  color: var(--color-primary);
  display: block;
}

.score-label {
  font-size: 1.25rem;
  color: var(--color-text-muted);
}

.end-message {
  font-size: 1.125rem;
  color: var(--color-text);
  margin-bottom: 1.5rem;
}

@media (max-width: 400px) {
  .card {
    padding: 1.5rem;
  }

  .question {
    font-size: 2rem;
  }

  .options {
    grid-template-columns: 1fr;
  }

  .icon-large {
    font-size: 3rem;
  }
}