:root {
    /* Primary Colors */
    --primary-color: #667eea;
    --primary-dark: #5568d3;
    --primary-light: #8093f1;
    --secondary-color: #764ba2;
    --accent-color: #ffd700;
    
    /* Status Colors */
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --error-color: #ef4444;
    --info-color: #3b82f6;
    
    /* Difficulty Colors */
    --difficulty-easy: #10b981;
    --difficulty-medium: #f59e0b;
    --difficulty-hard: #ef4444;
    --difficulty-expert: #8b5cf6;
    
    /* Neutral Colors */
    --white: #ffffff;
    --black: #000000;
    --gray-50: #f9fafb;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-300: #d1d5db;
    --gray-400: #9ca3af;
    --gray-500: #6b7280;
    --gray-600: #4b5563;
    --gray-700: #374151;
    --gray-800: #1f2937;
    --gray-900: #111827;
    
    /* Background */
    --bg-primary: #f9fafb;
    --bg-secondary: #ffffff;
    --bg-tertiary: #f3f4f6;
    
    /* Text Colors */
    --text-primary: #111827;
    --text-secondary: #6b7280;
    --text-light: #9ca3af;
    
    /* Border */
    --border-color: #e5e7eb;
    --border-radius-sm: 6px;
    --border-radius-md: 10px;
    --border-radius-lg: 15px;
    --border-radius-xl: 20px;
    --border-radius-full: 9999px;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    --spacing-3xl: 4rem;
    
    /* Font Sizes */
    --font-xs: 0.75rem;
    --font-sm: 0.875rem;
    --font-md: 1rem;
    --font-lg: 1.125rem;
    --font-xl: 1.25rem;
    --font-2xl: 1.5rem;
    --font-3xl: 1.875rem;
    --font-4xl: 2.25rem;
    
    /* Font Weights */
    --font-normal: 400;
    --font-medium: 500;
    --font-semibold: 600;
    --font-bold: 700;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    
    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-base: 300ms ease-in-out;
    --transition-slow: 500ms ease-in-out;
    
    /* Z-index */
    --z-dropdown: 1000;
    --z-modal: 2000;
    --z-tooltip: 3000;
    --z-notification: 4000;
    
    /* Breakpoints (for reference in JS) */
    --breakpoint-sm: 640px;
    --breakpoint-md: 768px;
    --breakpoint-lg: 1024px;
    --breakpoint-xl: 1280px;
    --breakpoint-2xl: 1536px;
}

/* Dark Mode Variables (Optional for future implementation) */
[data-theme="dark"] {
    --bg-primary: #111827;
    --bg-secondary: #1f2937;
    --bg-tertiary: #374151;
    --text-primary: #f9fafb;
    --text-secondary: #d1d5db;
    --text-light: #9ca3af;
    --border-color: #374151;
}