/* ============================================================================
   DUAL THEME SYSTEM - CSS Custom Properties
   Dark Mode (Default) & Light Mode Support
   ============================================================================ */

/* ============================================================================
   DEFAULT THEME (DARK MODE)
   ============================================================================ */

:root {
    /* ===== COLOR PRIMITIVES ===== */
    
    /* Primary Brand Colors */
    --color-primary-50: #eff6ff;
    --color-primary-100: #dbeafe;
    --color-primary-200: #bfdbfe;
    --color-primary-300: #93c5fd;
    --color-primary-400: #60a5fa;
    --color-primary-500: #3b82f6;
    --color-primary-600: #2563eb;
    --color-primary-700: #1d4ed8;
    --color-primary-800: #1e40af;
    --color-primary-900: #1e3a8a;
    
    /* Neutral Grays */
    --color-gray-50: #f9fafb;
    --color-gray-100: #f3f4f6;
    --color-gray-200: #e5e7eb;
    --color-gray-300: #d1d5db;
    --color-gray-400: #9ca3af;
    --color-gray-500: #6b7280;
    --color-gray-600: #4b5563;
    --color-gray-700: #374151;
    --color-gray-800: #1f2937;
    --color-gray-900: #111827;
    
    /* Success, Warning, Error */
    --color-success: #10b981;
    --color-success-light: #d1fae5;
    --color-warning: #f59e0b;
    --color-warning-light: #fef3c7;
    --color-error: #ef4444;
    --color-error-light: #fee2e2;
    --color-info: #3b82f6;
    --color-info-light: #dbeafe;
    
    /* ===== SEMANTIC TOKENS (DARK MODE) ===== */
    
    /* Backgrounds */
    --bg-body: #0a0a0a;
    --bg-surface: #111111;
    --bg-elevated: #1a1a1a;
    --bg-overlay: #1f1f1f;
    --bg-inverse: #ffffff;
    
    /* Text Colors */
    --text-primary: #ffffff;
    --text-secondary: #e5e5e5;
    --text-tertiary: #a3a3a3;
    --text-muted: #737373;
    --text-inverse: #0a0a0a;
    --text-link: var(--color-primary-400);
    --text-link-hover: var(--color-primary-300);
    
    /* Borders */
    --border-default: rgba(255, 255, 255, 0.1);
    --border-medium: rgba(255, 255, 255, 0.15);
    --border-strong: rgba(255, 255, 255, 0.25);
    --border-inverse: rgba(0, 0, 0, 0.1);
    --border-accent: var(--color-primary-500);
    
    /* Interactive States */
    --state-hover-bg: rgba(255, 255, 255, 0.05);
    --state-active-bg: rgba(255, 255, 255, 0.08);
    --state-focus-ring: var(--color-primary-500);
    --state-disabled-bg: rgba(255, 255, 255, 0.03);
    --state-disabled-text: var(--color-gray-600);
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.5);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.6), 0 2px 4px -1px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.7), 0 4px 6px -2px rgba(0, 0, 0, 0.5);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.8), 0 10px 10px -5px rgba(0, 0, 0, 0.6);
    --shadow-glow: 0 0 20px rgba(59, 130, 246, 0.3);
    
    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #3b82f6 0%, #1d4ed8 100%);
    --gradient-secondary: linear-gradient(135deg, #6b7280 0%, #374151 100%);
    --gradient-surface: linear-gradient(180deg, #1a1a1a 0%, #0a0a0a 100%);
    
    /* Opacity Levels */
    --opacity-disabled: 0.5;
    --opacity-subtle: 0.6;
    --opacity-medium: 0.8;
    
    /* Z-Index Scale */
    --z-dropdown: 1000;
    --z-sticky: 1020;
    --z-modal-backdrop: 1040;
    --z-modal: 1050;
    --z-popover: 1060;
    --z-tooltip: 1070;
    
    /* Spacing Scale (in rem) */
    --space-0: 0;
    --space-1: 0.25rem;
    --space-2: 0.5rem;
    --space-3: 0.75rem;
    --space-4: 1rem;
    --space-5: 1.25rem;
    --space-6: 1.5rem;
    --space-8: 2rem;
    --space-10: 2.5rem;
    --space-12: 3rem;
    --space-16: 4rem;
    --space-20: 5rem;
    
    /* Border Radius Scale */
    --radius-sm: 0.25rem;
    --radius-md: 0.375rem;
    --radius-lg: 0.5rem;
    --radius-xl: 0.75rem;
    --radius-2xl: 1rem;
    --radius-full: 9999px;
    
    /* Typography */
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-mono: ui-monospace, SFMono-Regular, 'SF Mono', Menlo, Monaco, 'Cascadia Code', 'Courier New', monospace;
    
    --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: 1.875rem;
    --font-size-4xl: 2.25rem;
    
    --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;
    
    /* Transitions */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
}

/* ============================================================================
   LIGHT MODE THEME
   ============================================================================ */

html.light-mode {
    /* ===== SEMANTIC TOKENS (LIGHT MODE) ===== */
    
    /* Backgrounds */
    --bg-body: #ffffff;
    --bg-surface: #f9fafb;
    --bg-elevated: #ffffff;
    --bg-overlay: #f3f4f6;
    --bg-inverse: #0a0a0a;
    
    /* Text Colors */
    --text-primary: #111827;
    --text-secondary: #374151;
    --text-tertiary: #6b7280;
    --text-muted: #9ca3af;
    --text-inverse: #ffffff;
    --text-link: var(--color-primary-600);
    --text-link-hover: var(--color-primary-700);
    
    /* Borders */
    --border-default: rgba(0, 0, 0, 0.1);
    --border-medium: rgba(0, 0, 0, 0.15);
    --border-strong: rgba(0, 0, 0, 0.25);
    --border-inverse: rgba(255, 255, 255, 0.1);
    --border-accent: var(--color-primary-600);
    
    /* Interactive States */
    --state-hover-bg: rgba(0, 0, 0, 0.04);
    --state-active-bg: rgba(0, 0, 0, 0.08);
    --state-focus-ring: var(--color-primary-600);
    --state-disabled-bg: rgba(0, 0, 0, 0.03);
    --state-disabled-text: var(--color-gray-400);
    
    /* 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), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    --shadow-glow: 0 0 20px rgba(59, 130, 246, 0.15);
    
    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #3b82f6 0%, #2563eb 100%);
    --gradient-secondary: linear-gradient(135deg, #9ca3af 0%, #6b7280 100%);
    --gradient-surface: linear-gradient(180deg, #ffffff 0%, #f9fafb 100%);
}

/* ============================================================================
   BASE ELEMENT STYLES
   ============================================================================ */

html {
    color-scheme: dark;
}

html.light-mode {
    color-scheme: light;
}

body {
    background-color: var(--bg-body);
    color: var(--text-primary);
    font-family: var(--font-sans);
    font-size: var(--font-size-base);
    line-height: var(--line-height-normal);
    transition: background-color var(--transition-base), color var(--transition-base);
}

/* ============================================================================
   COMPONENT UTILITY CLASSES
   ============================================================================ */

/* Surface/Card Components */
.surface {
    background-color: var(--bg-surface);
    border: 1px solid var(--border-default);
    border-radius: var(--radius-lg);
    padding: var(--space-4);
}

.surface-elevated {
    background-color: var(--bg-elevated);
    border: 1px solid var(--border-default);
    box-shadow: var(--shadow-md);
}

/* Text Utilities */
.text-primary { color: var(--text-primary); }
.text-secondary { color: var(--text-secondary); }
.text-tertiary { color: var(--text-tertiary); }
.text-muted { color: var(--text-muted); }
.text-inverse { color: var(--text-inverse); }

/* Background Utilities */
.bg-body { background-color: var(--bg-body); }
.bg-surface { background-color: var(--bg-surface); }
.bg-elevated { background-color: var(--bg-elevated); }
.bg-overlay { background-color: var(--bg-overlay); }

/* Border Utilities */
.border { border: 1px solid var(--border-default); }
.border-medium { border: 1px solid var(--border-medium); }
.border-strong { border: 1px solid var(--border-strong); }
.border-accent { border: 1px solid var(--border-accent); }

/* Interactive States */
.interactive {
    transition: background-color var(--transition-fast), 
                transform var(--transition-fast);
}

.interactive:hover {
    background-color: var(--state-hover-bg);
}

.interactive:active {
    background-color: var(--state-active-bg);
    transform: scale(0.98);
}

.interactive:focus-visible {
    outline: 2px solid var(--state-focus-ring);
    outline-offset: 2px;
}

.interactive:disabled {
    background-color: var(--state-disabled-bg);
    color: var(--state-disabled-text);
    cursor: not-allowed;
    opacity: var(--opacity-disabled);
}

/* Button Components */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
    padding: var(--space-2) var(--space-4);
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-medium);
    line-height: var(--line-height-tight);
    border: 1px solid transparent;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    text-decoration: none;
}

.btn:focus-visible {
    outline: 2px solid var(--state-focus-ring);
    outline-offset: 2px;
}

.btn-primary {
    background: var(--gradient-primary);
    color: var(--text-inverse);
    border-color: transparent;
}

.btn-primary:hover {
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background-color: var(--bg-surface);
    color: var(--text-primary);
    border-color: var(--border-default);
}

.btn-secondary:hover {
    background-color: var(--state-hover-bg);
    border-color: var(--border-medium);
}

.btn-ghost {
    background-color: transparent;
    color: var(--text-secondary);
}

.btn-ghost:hover {
    background-color: var(--state-hover-bg);
    color: var(--text-primary);
}

/* Input Components */
.input {
    width: 100%;
    padding: var(--space-2) var(--space-3);
    font-size: var(--font-size-sm);
    line-height: var(--line-height-normal);
    color: var(--text-primary);
    background-color: var(--bg-surface);
    border: 1px solid var(--border-default);
    border-radius: var(--radius-md);
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.input:hover {
    border-color: var(--border-medium);
}

.input:focus {
    outline: none;
    border-color: var(--border-accent);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.input::placeholder {
    color: var(--text-muted);
}

.input:disabled {
    background-color: var(--state-disabled-bg);
    color: var(--state-disabled-text);
    cursor: not-allowed;
}

/* Link Styles */
a {
    color: var(--text-link);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--text-link-hover);
    text-decoration: underline;
}

a:focus-visible {
    outline: 2px solid var(--state-focus-ring);
    outline-offset: 2px;
    border-radius: var(--radius-sm);
}

/* ============================================================================
   ACCESSIBILITY - REDUCED MOTION
   ============================================================================ */

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* ============================================================================
   THEME TOGGLE BUTTON
   ============================================================================ */

.theme-toggle {
    position: relative;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 2.5rem;
    height: 2.5rem;
    padding: 0;
    background-color: var(--bg-surface);
    border: 1px solid var(--border-default);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    font-size: 1.125rem;
    color: var(--text-secondary);
}

.theme-toggle:hover {
    background-color: var(--state-hover-bg);
    border-color: var(--border-medium);
    color: var(--text-primary);
    transform: translateY(-1px);
}

.theme-toggle:active {
    transform: translateY(0);
}

.theme-toggle:focus-visible {
    outline: 2px solid var(--state-focus-ring);
    outline-offset: 2px;
}

.theme-toggle-icon {
    transition: transform var(--transition-base);
}

.theme-toggle:hover .theme-toggle-icon {
    transform: rotate(20deg);
}

/* Icon visibility based on theme */
.theme-icon-dark {
    display: block;
}

.theme-icon-light {
    display: none;
}

html.light-mode .theme-icon-dark {
    display: none;
}

html.light-mode .theme-icon-light {
    display: block;
}

/* ============================================================================
   SCROLLBAR STYLING
   ============================================================================ */

* {
    scrollbar-width: thin;
    scrollbar-color: var(--color-primary-600) var(--bg-surface);
}

*::-webkit-scrollbar {
    width: 10px;
    height: 10px;
}

*::-webkit-scrollbar-track {
    background: var(--bg-surface);
}

*::-webkit-scrollbar-thumb {
    background: var(--gradient-primary);
    border-radius: var(--radius-full);
}

*::-webkit-scrollbar-thumb:hover {
    background: var(--color-primary-700);
}

/* ============================================================================
   SELECTION STYLING
   ============================================================================ */

::selection {
    background-color: var(--color-primary-500);
    color: var(--text-inverse);
}

::-moz-selection {
    background-color: var(--color-primary-500);
    color: var(--text-inverse);
}