/* CSS Custom Properties for theming and consistent spacing */
:root {
    /* Enhanced Color Scheme with more depth */
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --primary-light: #3b82f6;
    --secondary-color: #64748b;
    --secondary-hover: #475569;
    --background-light: #ffffff;
    --background-dark: #1e293b;
    --text-light: #1e293b;
    --text-dark: #f8fafc;
    --accent-color: #10b981;
    --accent-hover: #059669;
    --border-color: #e2e8f0;
    --border-hover: #cbd5e1;
    --hover-bg: #f1f5f9;
    --hover-bg-strong: #e2e8f0;
    --focus-ring: #3b82f6;
    --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);

    /* Spacing System (8px base unit) */
    --spacing-xs: 8px;
    --spacing-sm: 16px;
    --spacing-md: 24px;
    --spacing-lg: 32px;
    --spacing-xl: 40px;
    --spacing-2xl: 48px;

    /* Enhanced Typography with better hierarchy */
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
    --font-family-mono: 'SF Mono', 'Monaco', 'Inconsolata', 'Roboto Mono', 'Source Code Pro', monospace;
    --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;

    /* Layout */
    --sidebar-width: 280px;
    --header-height: 60px;
    --border-radius: 6px;
    --border-radius-lg: 12px;

    /* Enhanced Animation System */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-normal: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-bounce: 400ms cubic-bezier(0.68, -0.55, 0.265, 1.55);
    --ease-in-out: cubic-bezier(0.4, 0, 0.2, 1);
    --ease-out: cubic-bezier(0, 0, 0.2, 1);
    --ease-in: cubic-bezier(0.4, 0, 1, 1);
}

/* Reset and base styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: var(--font-family);
    background-color: var(--background-light);
    color: var(--text-light);
    line-height: 1.6;
    overflow-x: hidden;
}

/* Main layout container */
.app-container {
    display: grid;
    grid-template-areas:
        "header header"
        "sidebar main";
    grid-template-columns: var(--sidebar-width) 1fr;
    grid-template-rows: var(--header-height) 1fr;
    min-height: 100vh;
}

/* Enhanced Header with subtle animations */
.header {
    grid-area: header;
    background-color: var(--background-light);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    padding: 0 var(--spacing-md);
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(8px);
    box-shadow: var(--shadow-sm);
    transition: box-shadow var(--transition-normal), border-color var(--transition-normal);
}

.header:hover {
    box-shadow: var(--shadow-md);
    border-bottom-color: var(--border-hover);
}

.header h1 {
    font-size: 1.5rem;
    font-weight: var(--font-weight-semibold);
    color: var(--primary-color);
    transition: color var(--transition-fast);
}

/* Enhanced Sidebar with subtle depth */
.sidebar {
    grid-area: sidebar;
    background-color: var(--background-light);
    border-right: 1px solid var(--border-color);
    padding: var(--spacing-md);
    overflow-y: auto;
    height: calc(100vh - var(--header-height));
    position: sticky;
    top: var(--header-height);
    box-shadow: inset -1px 0 0 var(--border-color);
    transition: border-color var(--transition-normal);
}

.sidebar:hover {
    border-right-color: var(--border-hover);
}

/* Navigation Tree Styles */
.nav-tree {
    list-style: none;
    margin: 0;
    padding: 0;
}

.nav-section {
    margin-bottom: var(--spacing-xs);
}

.nav-section-header {
    display: flex;
    align-items: center;
    padding: var(--spacing-xs) var(--spacing-sm);
    cursor: pointer;
    border-radius: var(--border-radius);
    transition: all var(--transition-normal);
    user-select: none;
    font-weight: var(--font-weight-medium);
    color: var(--text-light);
    position: relative;
    overflow: hidden;
}

.nav-section-header:hover {
    background-color: var(--hover-bg);
}

.nav-section-header:focus {
    background-color: var(--hover-bg);
    outline: 2px solid var(--focus-ring);
    outline-offset: 2px;
}

.nav-section-header.active {
    background-color: var(--primary-color);
    color: white;
}

.nav-expand-icon {
    width: 16px;
    height: 16px;
    margin-right: var(--spacing-xs);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 12px;
    color: var(--secondary-color);
}

.nav-expand-icon.expanded {
    color: var(--primary-color);
}

.nav-section-title {
    flex: 1;
    font-size: 0.95rem;
}

.nav-subsections {
    list-style: none;
    margin: 0;
    padding: 0;
    margin-left: var(--spacing-md);
    border-left: 2px solid var(--border-color);
    display: none;
}

.nav-subsections.expanded {
    display: block;
    border-left-color: var(--primary-color);
}

.nav-subsection {
    margin: 0;
}

.nav-subsection-link {
    display: block;
    padding: var(--spacing-xs) var(--spacing-sm);
    margin-left: var(--spacing-sm);
    color: var(--secondary-color);
    text-decoration: none;
    border-radius: var(--border-radius);
    transition: all var(--transition-normal);
    font-size: 0.9rem;
    position: relative;
    overflow: hidden;
}

.nav-subsection-link:hover {
    background-color: var(--hover-bg);
    color: var(--text-light);
}

.nav-subsection-link:focus {
    background-color: var(--hover-bg);
    color: var(--text-light);
    outline: 2px solid var(--focus-ring);
    outline-offset: 2px;
}

.nav-subsection-link.active {
    background-color: var(--accent-color);
    color: white;
    font-weight: var(--font-weight-medium);
}

/* Enhanced Main content area */
.main-content {
    grid-area: main;
    padding: var(--spacing-md);
    overflow-y: auto;
    height: calc(100vh - var(--header-height));
    background-color: var(--background-light);
    position: relative;
}

.main-content::before {
    content: '';
    position: fixed;
    top: var(--header-height);
    right: 0;
    width: 1px;
    height: calc(100vh - var(--header-height));
    background: var(--border-color);
    opacity: 0.5;
    pointer-events: none;
}

/* Subtle scroll indicator */
.main-content::-webkit-scrollbar {
    width: 6px;
}

.main-content::-webkit-scrollbar-track {
    background: var(--hover-bg);
    border-radius: 3px;
}

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

.main-content::-webkit-scrollbar-thumb:hover {
    background: var(--primary-hover);
}

/* Enhanced Mobile Menu Button */
.mobile-menu-button {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--primary-color);
    cursor: pointer;
    padding: var(--spacing-xs);
    border-radius: var(--border-radius);
    transition: all var(--transition-normal);
    margin-right: var(--spacing-sm);
    position: relative;
    overflow: hidden;
}

.mobile-menu-button:hover {
    background-color: var(--hover-bg);
}

.mobile-menu-button:focus {
    outline: 2px solid var(--focus-ring);
    outline-offset: 2px;
}

/* Mobile Overlay */
.mobile-overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    z-index: 150;
    opacity: 0;
    transition: opacity var(--transition-normal);
}

.mobile-overlay.active {
    opacity: 1;
}

/* Enhanced Responsive Design */

/* Large Desktop (1440px+) */
@media (min-width: 1440px) {
    :root {
        --sidebar-width: 320px;
        --spacing-2xl: 64px;
    }

    .main-content {
        padding: var(--spacing-lg);
        max-width: 1200px;
        margin: 0 auto;
    }

    .welcome-features {
        grid-template-columns: repeat(4, 1fr);
    }

    .content-section {
        max-width: 900px;
    }
}

/* Desktop (1024px - 1439px) */
@media (min-width: 1024px) and (max-width: 1439px) {
    .main-content {
        padding: var(--spacing-md);
    }

    .welcome-features {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* Tablet Landscape (768px - 1023px) */
@media (min-width: 768px) and (max-width: 1023px) {
    :root {
        --sidebar-width: 260px;
    }

    .header h1 {
        font-size: 1.4rem;
    }

    .main-content {
        padding: var(--spacing-md);
    }

    .welcome-features {
        grid-template-columns: repeat(2, 1fr);
        gap: var(--spacing-sm);
    }

    .nav-section-header {
        padding: var(--spacing-sm);
    }

    .nav-subsection-link {
        padding: var(--spacing-sm);
        font-size: 0.95rem;
    }
}

/* Tablet Portrait and Mobile Landscape (481px - 767px) */
@media (max-width: 767px) {
    .mobile-menu-button {
        display: block;
    }

    .mobile-overlay {
        display: block;
    }

    .app-container {
        grid-template-areas:
            "header"
            "main";
        grid-template-columns: 1fr;
        grid-template-rows: var(--header-height) 1fr;
    }

    .sidebar {
        position: fixed;
        top: var(--header-height);
        left: -100%;
        width: min(var(--sidebar-width), 80vw);
        height: calc(100vh - var(--header-height));
        z-index: 200;
        transition: left var(--transition-normal);
        box-shadow: 2px 0 20px rgba(0, 0, 0, 0.15);
        background-color: var(--background-light);
    }

    .sidebar.open {
        left: 0;
    }

    .main-content {
        padding: var(--spacing-sm);
    }

    /* Touch-friendly navigation */
    .nav-section-header {
        padding: var(--spacing-md) var(--spacing-sm);
        min-height: 48px;
        display: flex;
        align-items: center;
        font-size: 1rem;
    }

    .nav-subsection-link {
        padding: var(--spacing-md) var(--spacing-sm);
        min-height: 44px;
        display: flex;
        align-items: center;
        font-size: 0.95rem;
        margin-left: var(--spacing-md);
    }

    .nav-expand-icon {
        width: 20px;
        height: 20px;
        font-size: 14px;
    }

    .welcome-features {
        grid-template-columns: 1fr;
        gap: var(--spacing-sm);
    }

    .welcome-feature {
        padding: var(--spacing-sm);
    }

    .content-section h2 {
        font-size: 1.75rem;
    }

    .content-section h3 {
        font-size: 1.25rem;
    }
}

/* Mobile Portrait (320px - 480px) */
@media (max-width: 480px) {
    :root {
        --spacing-xs: 6px;
        --spacing-sm: 12px;
        --spacing-md: 18px;
        --spacing-lg: 24px;
    }

    .header {
        padding: 0 var(--spacing-sm);
        min-height: var(--header-height);
    }

    .header h1 {
        font-size: 1.1rem;
        font-weight: 600;
    }

    .sidebar {
        width: min(280px, 85vw);
        padding: var(--spacing-sm);
    }

    .main-content {
        padding: var(--spacing-sm);
    }

    /* Extra touch-friendly for small screens */
    .nav-section-header {
        padding: var(--spacing-md);
        min-height: 52px;
        font-size: 1rem;
    }

    .nav-subsection-link {
        padding: var(--spacing-md);
        min-height: 48px;
        font-size: 0.9rem;
    }

    .nav-expand-icon {
        width: 24px;
        height: 24px;
        font-size: 16px;
        margin-right: var(--spacing-sm);
    }

    .welcome-content h2 {
        font-size: 1.75rem;
        margin-bottom: var(--spacing-sm);
    }

    .welcome-content p {
        font-size: 1rem;
        margin-bottom: var(--spacing-md);
    }

    .content-section h2 {
        font-size: 1.5rem;
        margin-bottom: var(--spacing-sm);
    }

    .content-section h3 {
        font-size: 1.1rem;
        margin: var(--spacing-md) 0 var(--spacing-xs) 0;
    }

    .article-link {
        padding: var(--spacing-sm);
        margin: var(--spacing-sm) 0;
    }

    .article-link h4 {
        font-size: 0.95rem;
        margin-bottom: var(--spacing-xs);
    }

    .article-link p {
        font-size: 0.85rem;
        line-height: 1.5;
    }
}

/* High DPI / Retina Display Optimizations */
@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
    .nav-expand-icon {
        font-weight: 500;
    }
    
    .nav-section-header,
    .nav-subsection-link {
        -webkit-font-smoothing: antialiased;
        -moz-osx-font-smoothing: grayscale;
    }
}

/* Reduced Motion Preferences */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
    
    .sidebar {
        transition: none;
    }
    
    .mobile-overlay {
        transition: none;
    }
    
    .content-container {
        transition: none;
    }
}

/* Dark Mode Support (if system preference) */
@media (prefers-color-scheme: dark) {
    :root {
        --background-light: #1e293b;
        --background-dark: #0f172a;
        --text-light: #f8fafc;
        --text-dark: #1e293b;
        --border-color: #334155;
        --hover-bg: #334155;
        --secondary-color: #94a3b8;
    }

    .mobile-overlay {
        background-color: rgba(0, 0, 0, 0.7);
    }

    .sidebar {
        box-shadow: 2px 0 20px rgba(0, 0, 0, 0.3);
    }
}

/* Utility classes for consistent spacing */
.mb-xs {
    margin-bottom: var(--spacing-xs);
}

.mb-sm {
    margin-bottom: var(--spacing-sm);
}

.mb-md {
    margin-bottom: var(--spacing-md);
}

.mb-lg {
    margin-bottom: var(--spacing-lg);
}

.mt-xs {
    margin-top: var(--spacing-xs);
}

.mt-sm {
    margin-top: var(--spacing-sm);
}

.mt-md {
    margin-top: var(--spacing-md);
}

.mt-lg {
    margin-top: var(--spacing-lg);
}

.p-xs {
    padding: var(--spacing-xs);
}

.p-sm {
    padding: var(--spacing-sm);
}

.p-md {
    padding: var(--spacing-md);
}

.p-lg {
    padding: var(--spacing-lg);
}

/* Enhanced Content area styles */
.article-link {
    background-color: var(--hover-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-md);
    margin: var(--spacing-md) 0;
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.article-link:hover {
    box-shadow: var(--shadow-lg);
    border-color: var(--border-hover);
}

.article-link h4 {
    margin-bottom: var(--spacing-sm);
    font-weight: var(--font-weight-semibold);
}

.article-link h4 a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: var(--font-weight-semibold);
    transition: all var(--transition-fast);
}

.article-link h4 a:hover {
    color: var(--accent-color);
}

.article-link p {
    color: var(--secondary-color);
    line-height: var(--line-height-relaxed);
    margin: 0;
    font-weight: var(--font-weight-normal);
}

/* Enhanced Focus styles for accessibility */
*:focus {
    outline: 2px solid var(--focus-ring);
    outline-offset: 2px;
    transition: outline-color var(--transition-fast);
}

*:focus:not(:focus-visible) {
    outline: none;
}

*:focus-visible {
    outline: 2px solid var(--focus-ring);
    outline-offset: 2px;
    box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.1);
}

/* Smooth scrolling */
html {
    scroll-behavior: smooth;
}

/* Simplified Dynamic Content Display Styles */
.content-container {
    opacity: 1;
    transition: opacity var(--transition-normal);
}

.content-container.fade-out {
    opacity: 0;
}

.content-container.fade-in {
    opacity: 1;
}

.content-section {
    max-width: 800px;
    margin: 0 auto;
}

.content-section h2 {
    color: var(--primary-color);
    font-size: 2rem;
    font-weight: var(--font-weight-bold);
    margin-bottom: var(--spacing-md);
    border-bottom: 3px solid var(--primary-color);
    padding-bottom: var(--spacing-sm);
    position: relative;
    line-height: var(--line-height-tight);
}

.content-section h2::after {
    content: '';
    position: absolute;
    bottom: -3px;
    left: 0;
    width: 60px;
    height: 3px;
    background: var(--primary-color);
    border-radius: 2px;
}

.content-section h3 {
    color: var(--text-light);
    font-size: 1.5rem;
    font-weight: var(--font-weight-semibold);
    margin: var(--spacing-lg) 0 var(--spacing-sm) 0;
    line-height: var(--line-height-tight);
    position: relative;
    padding-left: var(--spacing-sm);
}

.content-section h3::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 4px;
    height: 20px;
    background: var(--accent-color);
    border-radius: 2px;
}

.content-section p {
    margin-bottom: var(--spacing-sm);
    line-height: var(--line-height-relaxed);
    color: var(--secondary-color);
    font-weight: var(--font-weight-normal);
}

.coming-soon-placeholder {
    text-align: center;
    padding: var(--spacing-2xl);
    background-color: var(--hover-bg);
    border-radius: var(--border-radius-lg);
    border: 2px dashed var(--border-color);
    margin: var(--spacing-md) 0;
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.coming-soon-placeholder:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-md);
}

.coming-soon-placeholder h3 {
    color: var(--secondary-color);
    font-size: 1.25rem;
    margin-bottom: var(--spacing-sm);
    font-weight: var(--font-weight-semibold);
    position: relative;
    z-index: 1;
}

.coming-soon-placeholder p {
    color: var(--secondary-color);
    font-size: 0.95rem;
    opacity: 0.8;
    line-height: var(--line-height-normal);
    font-weight: var(--font-weight-normal);
    position: relative;
    z-index: 1;
}

.coming-soon-placeholder .icon {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: var(--spacing-sm);
    opacity: 0.8;
}

.welcome-content {
    text-align: center;
    padding: var(--spacing-2xl);
    max-width: 600px;
    margin: 0 auto;
}

.welcome-content h2 {
    color: var(--primary-color);
    font-size: 2.5rem;
    font-weight: var(--font-weight-bold);
    margin-bottom: var(--spacing-md);
    border: none;
    padding: 0;
    line-height: var(--line-height-tight);
}

.welcome-content p {
    font-size: 1.1rem;
    color: var(--secondary-color);
    line-height: var(--line-height-relaxed);
    margin-bottom: var(--spacing-lg);
    font-weight: var(--font-weight-normal);
}



.welcome-features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-md);
    margin-top: var(--spacing-lg);
}

.welcome-feature {
    background-color: var(--hover-bg);
    padding: var(--spacing-md);
    border-radius: var(--border-radius-lg);
    border: 1px solid var(--border-color);
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.welcome-feature:hover {
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.welcome-feature h4 {
    color: var(--primary-color);
    font-size: 1rem;
    font-weight: var(--font-weight-semibold);
    margin-bottom: var(--spacing-xs);
    position: relative;
    z-index: 1;
}

.welcome-feature p {
    font-size: 0.9rem;
    color: var(--secondary-color);
    margin: 0;
    line-height: var(--line-height-normal);
    font-weight: var(--font-weight-normal);
    position: relative;
    z-index: 1;
}