/* CSS Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: 2rem;
}

:root {
    /* Light mode colors */
    --color-primary: #2563eb;
    --color-primary-hover: #1d4ed8;
    --color-secondary: #64748b;
    --color-accent: #0ea5e9;
    
    --color-background: #ffffff;
    --color-surface: #f8fafc;
    --color-surface-elevated: #ffffff;
    
    --color-text-primary: #0f172a;
    --color-text-secondary: #475569;
    --color-text-muted: #64748b;
    
    --color-border: #e2e8f0;
    --color-border-hover: #cbd5e1;
    
    --color-success: #10b981;
    --color-warning: #f59e0b;
    --color-error: #ef4444;
    
    /* 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;
    
    /* Typography */
    --font-family: 'Inter', -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: 1.875rem;
    --font-size-4xl: 2.25rem;
    
    /* 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);
    
    /* Border radius */
    --radius-sm: 0.25rem;
    --radius-md: 0.375rem;
    --radius-lg: 0.5rem;
    --radius-xl: 0.75rem;
    
    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-normal: 250ms ease-in-out;
    --transition-slow: 350ms ease-in-out;
    
    /* Layout */
    --header-height: 4rem;
    --sidebar-width: 280px;
    --sidebar-width-mobile: 100vw;
}

/* Dark mode colors */
[data-theme="dark"] {
    --color-background: #0f172a;
    --color-surface: #1e293b;
    --color-surface-elevated: #334155;
    
    --color-text-primary: #f1f5f9;
    --color-text-secondary: #cbd5e1;
    --color-text-muted: #94a3b8;
    
    --color-border: #334155;
    --color-border-hover: #475569;
}

/* Auto detect system preference */
@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
        --color-background: #0f172a;
        --color-surface: #1e293b;
        --color-surface-elevated: #334155;
        
        --color-text-primary: #f1f5f9;
        --color-text-secondary: #cbd5e1;
        --color-text-muted: #94a3b8;
        
        --color-border: #334155;
        --color-border-hover: #475569;
    }
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--color-text-primary);
    background-color: var(--color-background);
    transition: background-color var(--transition-normal), color var(--transition-normal);
}

/* Skip link for accessibility */
.scroll-progress-bar,
#scroll-progress-bar {
    position: fixed;
    top: 0;
    left: 0;
    width: 0%;
    height: 4px;
    background: linear-gradient(90deg, var(--color-accent), var(--color-primary));
    z-index: 9999;
    border-radius: 0 0 2px 2px;
    box-shadow: 0 2px 8px rgba(37,99,235,0.10);
    transition: width 0.2s cubic-bezier(.4,0,.2,1);
    pointer-events: none;
}
.skip-link {
    position: absolute;
    top: -40px;
    left: 6px;
    background: var(--color-primary);
    color: white;
    padding: 8px;
    text-decoration: none;
    border-radius: var(--radius-md);
    z-index: 1000;
    transition: top var(--transition-fast);
}

.skip-link:focus {
    top: 6px;
}

/* Container */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

/* Header */
.header {
    position: sticky;
    top: 0;
    z-index: 100;
    background-color: var(--color-surface-elevated);
    border-bottom: 1px solid var(--color-border);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    transition: all var(--transition-normal);
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: var(--header-height);
}

.logo {
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--color-text-primary);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    text-decoration: none;
}

.logo-icon {
    font-size: var(--font-size-2xl);
}

/* Theme Toggle */
.theme-toggle {
    position: relative;
    width: 48px;
    height: 48px;
    border: none;
    background: var(--color-surface);
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all var(--transition-normal);
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--color-border);
}

.theme-toggle:hover {
    background: var(--color-surface-elevated);
    border-color: var(--color-border-hover);
    transform: translateY(-1px);
}

.theme-toggle:focus {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

.theme-toggle-icon {
    position: absolute;
    width: 20px;
    height: 20px;
    color: var(--color-text-primary);
    transition: all var(--transition-normal);
}

.theme-toggle-icon.dark-icon {
    opacity: 0;
    transform: rotate(180deg);
}

[data-theme="dark"] .theme-toggle-icon.light-icon {
    opacity: 0;
    transform: rotate(180deg);
}

[data-theme="dark"] .theme-toggle-icon.dark-icon {
    opacity: 1;
    transform: rotate(0deg);
}

/* Main Layout */
.main-wrapper {
    display: flex;
    min-height: calc(100vh - var(--header-height));
}

/* Sidebar */
.sidebar {
    position: sticky;
    top: var(--header-height);
    width: var(--sidebar-width);
    height: calc(100vh - var(--header-height));
    background-color: var(--color-surface);
    border-right: 1px solid var(--color-border);
    overflow-y: auto;
    overflow-x: hidden;
    transition: all var(--transition-normal);
}

/* Custom Scrollbar for Sidebar */
.sidebar::-webkit-scrollbar {
    width: 6px;
}

.sidebar::-webkit-scrollbar-track {
    background: var(--color-surface);
}

.sidebar::-webkit-scrollbar-thumb {
    background: var(--color-border-hover);
    border-radius: 3px;
    transition: background var(--transition-normal);
}

.sidebar::-webkit-scrollbar-thumb:hover {
    background: var(--color-text-muted);
}

/* Firefox Scrollbar */
.sidebar {
    scrollbar-width: thin;
    scrollbar-color: var(--color-border-hover) var(--color-surface);
}

.sidebar-nav {
    padding: var(--spacing-xl) 0;
}

.sidebar-title {
    font-size: var(--font-size-sm);
    font-weight: 600;
    color: var(--color-text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: var(--spacing-lg);
}

.sidebar-menu {
    list-style: none;
}

.sidebar-menu li {
    margin-bottom: var(--spacing-xs);
}

.sidebar-link {
    display: block;
    padding: var(--spacing-sm) var(--spacing-lg);
    margin: 0 var(--spacing-lg);
    color: var(--color-text-secondary);
    text-decoration: none;
    border-radius: var(--radius-md);
    font-size: var(--font-size-sm);
    font-weight: 500;
    transition: all var(--transition-normal);
    position: relative;
}

.sidebar-link:hover {
    background-color: var(--color-surface-elevated);
    color: var(--color-text-primary);
    transform: translateX(2px);
}

.sidebar-link:focus {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}


.sidebar-link.active,
.sidebar-link[aria-current="page"] {
    background-color: var(--color-primary);
    color: white;
    box-shadow: 0 2px 8px rgba(37, 99, 235, 0.08);
    border-radius: var(--radius-lg);
    position: relative;
    z-index: 1;
    padding-left: calc(var(--spacing-lg) + 4px);
    border: 1.5px solid var(--color-accent);
}

.sidebar-link.active::before {
    content: '';
    position: absolute;
    left: -4px;
    top: 8px;
    bottom: 8px;
    width: 6px;
    background-color: var(--color-accent);
    border-radius: var(--radius-lg);
    box-shadow: 0 0 8px 2px rgba(14, 165, 233, 0.15);
}

/* Mobile Menu Toggle */
.mobile-menu-toggle {
    display: none;
    position: fixed;
    top: 1rem;
    right: 1rem;
    width: 48px;
    height: 48px;
    background: var(--color-surface-elevated);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    cursor: pointer;
    z-index: 200;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 4px;
}

.hamburger {
    width: 20px;
    height: 2px;
    background: var(--color-text-primary);
    transition: all var(--transition-normal);
}

.mobile-menu-toggle[aria-expanded="true"] .hamburger:nth-child(1) {
    transform: rotate(45deg) translate(6px, 6px);
}

.mobile-menu-toggle[aria-expanded="true"] .hamburger:nth-child(2) {
    opacity: 0;
}

.mobile-menu-toggle[aria-expanded="true"] .hamburger:nth-child(3) {
    transform: rotate(-45deg) translate(6px, -6px);
}

/* Main Content */
.main-content {
    flex: 1;
    min-width: 0;
}

.content-wrapper {
    max-width: 800px;
    margin: 0 auto;
    padding: var(--spacing-3xl) var(--spacing-xl);
}

/* Page Header */
.page-header {
    margin-bottom: var(--spacing-3xl);
    text-align: center;
}

.page-title {
    font-size: var(--font-size-4xl);
    font-weight: 700;
    color: var(--color-text-primary);
    margin-bottom: var(--spacing-md);
    line-height: 1.2;
}

.page-subtitle {
    font-size: var(--font-size-lg);
    color: var(--color-text-secondary);
}

/* Content Sections */
.content-section {
    margin-bottom: var(--spacing-3xl);
    scroll-margin-top: calc(var(--header-height) + var(--spacing-xl));
}

.section-title {
    font-size: var(--font-size-2xl);
    font-weight: 600;
    color: var(--color-text-primary);
    margin-bottom: var(--spacing-lg);
    line-height: 1.3;
}

.section-content {
    color: var(--color-text-secondary);
    line-height: 1.7;
}

.section-content p {
    margin-bottom: var(--spacing-lg);
}

.section-content p:last-child {
    margin-bottom: 0;
}

/* Links */
a {
    color: var(--color-primary);
    text-decoration: underline;
    text-decoration-color: transparent;
    transition: all var(--transition-normal);
}

a:hover {
    color: var(--color-primary-hover);
    text-decoration-color: currentColor;
}

a:focus {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
    border-radius: var(--radius-sm);
}

/* Lists */
.styled-list {
    list-style: none;
    margin: var(--spacing-lg) 0;
}

.styled-list li {
    position: relative;
    padding-left: var(--spacing-lg);
    margin-bottom: var(--spacing-sm);
}

.styled-list li::before {
    content: '•';
    position: absolute;
    left: 0;
    color: var(--color-primary);
    font-weight: bold;
}

/* Special Boxes */
.highlight-box,
.info-box {
    padding: var(--spacing-xl);
    border-radius: var(--radius-xl);
    margin: var(--spacing-xl) 0;
    border-left: 4px solid var(--color-primary);
}

.highlight-box {
    background-color: var(--color-surface);
    border-left-color: var(--color-accent);
}

.info-box {
    background-color: var(--color-surface);
    border-left-color: var(--color-success);
}

.highlight-title,
.info-box h3 {
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--color-text-primary);
    margin-bottom: var(--spacing-md);
}

/* Contact Info */
.contact-info {
    background-color: var(--color-surface);
    padding: var(--spacing-xl);
    border-radius: var(--radius-xl);
    margin-top: var(--spacing-xl);
}

.contact-info p {
    margin-bottom: var(--spacing-sm);
}

.contact-info p:last-child {
    margin-bottom: 0;
}

/* Footer */
.footer {
    background-color: var(--color-surface);
    border-top: 1px solid var(--color-border);
    margin-top: var(--spacing-3xl);
}

.footer-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-xl) 0;
    color: var(--color-text-muted);
    font-size: var(--font-size-sm);
}

.footer-nav {
    display: flex;
    gap: var(--spacing-lg);
}

.footer-link {
    color: var(--color-text-muted);
    text-decoration: none;
    transition: color var(--transition-normal);
}

.footer-link:hover {
    color: var(--color-text-primary);
}

/* Safari Reader Mode Compatibility */
@media screen and (-webkit-min-device-pixel-ratio: 0) {
    .sidebar {
        -webkit-overflow-scrolling: touch;
    }
}

/* Enhanced SEO and Accessibility */
.page-header time {
    font-weight: 500;
}

/* Structured Data Styling */
.content-section[itemscope] {
    position: relative;
}

/* Responsive Design */
@media (max-width: 768px) {
    .sidebar {
        position: fixed;
        top: 0;
        left: 0;
        width: var(--sidebar-width-mobile);
        height: 100vh;
        z-index: 150;
        transform: translateX(-100%);
        transition: transform var(--transition-normal);
    }
    
    .sidebar.mobile-open {
        transform: translateX(0);
    }
    
    .mobile-menu-toggle {
        display: flex;
    }
    
    .main-content {
        width: 100%;
    }
    
    .content-wrapper {
        padding: var(--spacing-xl) var(--spacing-lg);
    }
    
    .page-title {
        font-size: var(--font-size-3xl);
    }
    
    .section-title {
        font-size: var(--font-size-xl);
    }
    
    .footer-content {
        flex-direction: column;
        gap: var(--spacing-md);
        text-align: center;
    }
    
    .footer-nav {
        gap: var(--spacing-md);
    }
}

@media (max-width: 480px) {
    .content-wrapper {
        padding: var(--spacing-lg) var(--spacing-md);
    }
    
    .page-title {
        font-size: var(--font-size-2xl);
    }
    
    .highlight-box,
    .info-box,
    .contact-info {
        padding: var(--spacing-lg);
    }
}

/* Smooth animations */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.content-section {
    animation: fadeInUp 0.6s ease-out;
}

/* Focus visible for better accessibility */
@supports selector(:focus-visible) {
    a:focus {
        outline: none;
    }
    
    a:focus-visible {
        outline: 2px solid var(--color-primary);
        outline-offset: 2px;
    }
}

/* Reduce motion for accessibility */
@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }
    
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* High contrast mode support */
@media (prefers-contrast: high) {
    :root {
        --color-border: #000000;
        --color-text-secondary: #000000;
    }
    
    [data-theme="dark"] {
        --color-border: #ffffff;
        --color-text-secondary: #ffffff;
    }
}

/* Print styles */
@media print {
    .header,
    .sidebar,
    .footer,
    .theme-toggle,
    .mobile-menu-toggle {
        display: none !important;
    }
    
    .main-content {
        width: 100% !important;
    }
    
    .content-wrapper {
        max-width: none !important;
        padding: 0 !important;
    }
    
    a {
        color: #000000 !important;
        text-decoration: underline !important;
    }
}