:root {
    /* 
     * Monochrome Theme - dgray.io
     * Pure grayscale, no colors
     */
    
    /* Colors - Light Mode */
    --color-primary: #555555;
    --color-primary-hover: #404040;
    --color-primary-light: #E8E8E8;
    
    --color-secondary: #777777;
    --color-secondary-hover: #5A5A5A;
    
    --color-accent: #333333;
    --color-accent-hover: #1A1A1A;
    
    --color-success: #666666;
    --color-warning: #888888;
    --color-error: #444444;
    
    --color-bg: #FAFAFA;
    --color-bg-secondary: #F0F0F0;
    --color-bg-tertiary: #E5E5E5;
    
    --color-text: #1A1A1A;
    --color-text-secondary: #4A4A4A;
    --color-text-muted: #8A8A8A;
    
    --color-border: #D0D0D0;
    --color-border-focus: #555555;
    
    --color-shadow: rgba(0, 0, 0, 0.1);
    --color-overlay: rgba(0, 0, 0, 0.5);
    
    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
    --space-3xl: 4rem;
    
    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-family-heading: 'Space Grotesk', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 2rem;
    
    --font-weight-normal: 400;
    --font-weight-medium: 500;
    --font-weight-semibold: 600;
    --font-weight-bold: 700;
    
    --line-height-tight: 1.25;
    --line-height-normal: 1.5;
    --line-height-relaxed: 1.75;
    
    /* Border Radius */
    --radius-sm: 0.25rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-full: 9999px;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px var(--color-shadow);
    --shadow-md: 0 4px 6px var(--color-shadow);
    --shadow-lg: 0 10px 15px var(--color-shadow);
    --shadow-xl: 0 20px 25px var(--color-shadow);
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --transition-slow: 350ms ease;
    
    /* Layout */
    --header-height: 4rem;
    --footer-height: 3rem;
    --container-max: 1200px;
    --sidebar-width: 280px;
    
    /* Z-Index */
    --z-dropdown: 100;
    --z-sticky: 200;
    --z-modal: 300;
    --z-toast: 400;
}

/* Dark Mode - System Preference */
@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
        --color-primary: #AAAAAA;
        --color-primary-hover: #C0C0C0;
        --color-primary-light: #2A2A2A;
        
        --color-secondary: #909090;
        --color-secondary-hover: #A5A5A5;
        
        --color-accent: #CCCCCC;
        --color-accent-hover: #E0E0E0;
        
        --color-success: #999999;
        --color-warning: #AAAAAA;
        --color-error: #888888;
        
        --color-bg: #141414;
        --color-bg-secondary: #1E1E1E;
        --color-bg-tertiary: #2A2A2A;
        
        --color-text: #F0F0F0;
        --color-text-secondary: #C0C0C0;
        --color-text-muted: #808080;
        
        --color-border: #3A3A3A;
        --color-border-focus: #AAAAAA;
        
        --color-shadow: rgba(0, 0, 0, 0.4);
        --color-overlay: rgba(0, 0, 0, 0.7);
    }
}

/* Dark Mode - Manual Override */
[data-theme="dark"] {
    --color-primary: #AAAAAA;
    --color-primary-hover: #C0C0C0;
    --color-primary-light: #2A2A2A;
    
    --color-secondary: #909090;
    --color-secondary-hover: #A5A5A5;
    
    --color-accent: #CCCCCC;
    --color-accent-hover: #E0E0E0;
    
    --color-success: #999999;
    --color-warning: #AAAAAA;
    --color-error: #888888;
    
    --color-bg: #141414;
    --color-bg-secondary: #1E1E1E;
    --color-bg-tertiary: #2A2A2A;
    
    --color-text: #F0F0F0;
    --color-text-secondary: #C0C0C0;
    --color-text-muted: #808080;
    
    --color-border: #3A3A3A;
    --color-border-focus: #AAAAAA;
    
    --color-shadow: rgba(0, 0, 0, 0.4);
    --color-overlay: rgba(0, 0, 0, 0.7);
}

/* Light Mode - Manual Override */
[data-theme="light"] {
    --color-primary: #555555;
    --color-primary-hover: #404040;
    --color-primary-light: #E8E8E8;
    
    --color-secondary: #777777;
    --color-secondary-hover: #5A5A5A;
    
    --color-accent: #333333;
    --color-accent-hover: #1A1A1A;
    
    --color-success: #666666;
    --color-warning: #888888;
    --color-error: #444444;
    
    --color-bg: #FAFAFA;
    --color-bg-secondary: #F0F0F0;
    --color-bg-tertiary: #E5E5E5;
    
    --color-text: #1A1A1A;
    --color-text-secondary: #4A4A4A;
    --color-text-muted: #8A8A8A;
    
    --color-border: #D0D0D0;
    --color-border-focus: #555555;
    
    --color-shadow: rgba(0, 0, 0, 0.1);
    --color-overlay: rgba(0, 0, 0, 0.5);
}