:root {
  --primary-color: #667eea;
  --secondary-color: #764ba2;
  --success-color: #4ade80;
  --danger-color: #f87171;
  --warning-color: #fbbf24;
  
  --bg-color: #f8fafc;
  --card-bg: #ffffff;
  --text-primary: #1e293b;
  --text-secondary: #64748b;
  --border-color: #e2e8f0;
  
  --shadow: 0 4px 6px -1px rgba(0,0,0,0.1);
  --shadow-lg: 0 20px 25px -5px rgba(0,0,0,0.1);
  
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
}

[data-theme="dark"] {
  --bg-color: #0f172a;
  --card-bg: #1e293b;
  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --border-color: #334155;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background: var(--bg-color);
  color: var(--text-primary);
  line-height: 1.6;
  transition: background 0.3s ease, color 0.3s ease;
  min-height: 100vh;
}

.main-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 2rem;
  min-height: calc(100vh - 200px);
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: white;
  border: none;
  padding: 1rem 2rem;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s ease;
}

.btn-primary:hover:not(:disabled) {
  transform: translateY(-2px);
}

.btn-primary:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.btn-secondary {
  background: var(--card-bg);
  color: var(--text-primary);
  border: 2px solid var(--border-color);
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-md);
  font-size: 0.95rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.3s ease;
}

.btn-secondary:hover:not(:disabled) {
  border-color: var(--primary-color);
  transform: translateY(-2px);
}

.btn-secondary:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* Game setup styles */
.setup-screen {
  text-align: center;
  padding: 2rem;
}

.game-title {
  font-size: 3rem;
  font-weight: bold;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 0.5rem;
}

.game-tagline {
  font-size: 1.2rem;
  color: var(--text-secondary);
  margin-bottom: 3rem;
}

.mode-selector {
  margin-bottom: 2rem;
}

.mode-selector h2 {
  margin-bottom: 1.5rem;
  color: var(--text-primary);
}

.mode-cards {
  display: flex;
  gap: 1.5rem;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 2rem;
}

.mode-card {
  background: var(--card-bg);
  border: 3px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 2rem;
  cursor: pointer;
  transition: all 0.3s ease;
  min-width: 200px;
  text-align: center;
}

.mode-card:hover {
  border-color: var(--primary-color);
  transform: translateY(-4px);
}

.mode-card.active {
  border-color: var(--primary-color);
  background: linear-gradient(135deg, rgba(102, 126, 234, 0.1), rgba(118, 75, 162, 0.1));
}

.mode-icon {
  font-size: 3rem;
  display: block;
  margin-bottom: 1rem;
}

.mode-card h3 {
  margin-bottom: 0.5rem;
  color: var(--text-primary);
}

.mode-card p {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.ai-settings {
  background: var(--card-bg);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 2rem;
  margin: 2rem auto;
  max-width: 500px;
}

.setting-group {
  margin-bottom: 1.5rem;
}

.setting-group label {
  display: block;
  margin-bottom: 1rem;
  font-weight: 600;
  color: var(--text-primary);
}

.difficulty-buttons,
.first-move-buttons {
  display: flex;
  gap: 1rem;
  justify-content: center;
}

.diff-btn,
.first-btn {
  flex: 1;
  padding: 0.75rem 1rem;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  background: var(--card-bg);
  color: var(--text-primary);
  cursor: pointer;
  transition: all 0.3s ease;
  font-weight: 500;
}

.diff-btn:hover,
.first-btn:hover {
  border-color: var(--primary-color);
}

.diff-btn.active,
.first-btn.active {
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: white;
  border-color: var(--primary-color);
}

/* Game screen styles */
.game-screen {
  padding: 2rem;
}

.game-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 2rem;
  flex-wrap: wrap;
  gap: 1rem;
}

.game-info {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.game-status {
  font-size: 1.5rem;
  font-weight: bold;
  color: var(--text-primary);
}

.stats-mini {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.game-controls {
  display: flex;
  gap: 1rem;
  justify-content: center;
  margin-top: 2rem;
  flex-wrap: wrap;
}

/* Responsive */
@media (max-width: 768px) {
  .main-container {
    padding: 1rem;
  }
  
  .btn-primary, .btn-secondary {
    padding: 0.75rem 1.25rem;
    font-size: 0.9rem;
  }
  
  .game-title {
    font-size: 2rem;
  }
  
  .game-tagline {
    font-size: 1rem;
  }
  
  .mode-cards {
    flex-direction: column;
    align-items: center;
  }
  
  .mode-card {
    width: 100%;
    max-width: 300px;
  }
  
  .difficulty-buttons,
  .first-move-buttons {
    flex-direction: column;
  }
  
  .game-header {
    flex-direction: column;
    align-items: stretch;
  }
}