:root {
  --primary: #4a90e2;
  --primary-dark: #326ac0;
  --secondary: #38a169;
  --gray-100: #f7fafc;
  --gray-600: #718096;
  --card-bg: #ffffff;
}

/* Example dark theme override; apply class="theme-dark" on <html> to activate */
.theme-dark {
  --primary: #90cdf4;
  --primary-dark: #63b3ed;
  --secondary: #9ae6b4;
  --card-bg: #2d3748;
  --gray-100: #1a202c;
  --gray-600: #a0aec0;
}

/* Utility helpers */
.btn-primary { background-color: var(--primary); color: #fff; }
.btn-primary:hover { background-color: var(--primary-dark); }