/* ============================================
   MODERN SYSTEM HELP GUIDE - STYLES 2026
   Responsive, Beautiful, and Optimized
   ============================================ */

/* ============================================
   CSS VARIABLES & THEME COLORS
   ============================================ */
:root {
    /* Primary Colors */
    --primary-color: #667eea;
    --primary-dark: #5568d3;
    --primary-light: #7c94f5;
    --secondary-color: #764ba2;
    --accent-color: #f093fb;
    
    /* Neutral Colors */
    --bg-color: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-tertiary: #e9ecef;
    --text-color: #2d3748;
    --text-secondary: #718096;
    --text-muted: #a0aec0;
    
    /* Border & Shadow */
    --border-color: #e2e8f0;
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.15);
    --shadow-xl: 0 20px 60px rgba(0, 0, 0, 0.2);
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-full: 9999px;
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 350ms ease;
    
    /* Fonts */
    --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-heading: 'Poppins', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

/* Dark Mode Variables */
[data-theme="dark"] {
    --bg-color: #1a202c;
    --bg-secondary: #2d3748;
    --bg-tertiary: #4a5568;
    --text-color: #f7fafc;
    --text-secondary: #e2e8f0;
    --text-muted: #cbd5e0;
    --border-color: #4a5568;
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.5);
    --shadow-xl: 0 20px 60px rgba(0, 0, 0, 0.6);
}

/* ============================================
   RESET & BASE STYLES
   ============================================ */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: var(--font-primary);
    color: var(--text-color);
    background-color: var(--bg-color);
    line-height: 1.6;
    overflow-x: hidden;
    transition: background-color var(--transition-base), color var(--transition-base);
}

/* ============================================
   LOADING SCREEN
   ============================================ */
.loading-screen {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 10000;
    transition: opacity 0.5s ease, visibility 0.5s ease;
}

.loading-screen.hidden {
    opacity: 0;
    visibility: hidden;
}

.loading-content {
    text-align: center;
    color: white;
}

.loading-spinner {
    width: 60px;
    height: 60px;
    border: 4px solid rgba(255, 255, 255, 0.3);
    border-top-color: white;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 1.5rem;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.loading-content h2 {
    font-family: var(--font-heading);
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
}

.loading-content p {
    font-size: 1rem;
    opacity: 0.9;
}

/* ============================================
   READING PROGRESS BAR
   ============================================ */
.reading-progress {
    position: fixed;
    top: 0;
    left: 0;
    width: 0%;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
    z-index: 9999;
    transition: width 0.1s ease;
}

/* ============================================
   CONTAINER
   ============================================ */
.container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

@media (max-width: 768px) {
    .container {
        padding: 0 var(--spacing-md);
    }
}

/* ============================================
   HEADER
   ============================================ */
.header {
    position: sticky;
    top: 0;
    background: var(--bg-color);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    transition: all var(--transition-base);
    backdrop-filter: blur(10px);
    background: rgba(255, 255, 255, 0.95);
}

[data-theme="dark"] .header {
    background: rgba(26, 32, 44, 0.95);
}

.header.scrolled {
    box-shadow: var(--shadow-md);
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-md) 0;
    gap: var(--spacing-lg);
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-family: var(--font-heading);
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--primary-color);
    text-decoration: none;
}

.logo-icon {
    font-size: 1.75rem;
}

.nav-menu {
    display: flex;
    gap: var(--spacing-md);
}

.nav-link {
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-secondary);
    text-decoration: none;
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    font-weight: 500;
}

.nav-link:hover {
    color: var(--primary-color);
    background: var(--bg-secondary);
}

.nav-link.active {
    color: var(--primary-color);
    background: var(--bg-secondary);
}

.header-actions {
    display: flex;
    gap: var(--spacing-sm);
    align-items: center;
}

.icon-btn {
    width: 40px;
    height: 40px;
    border: none;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    transition: all var(--transition-fast);
}

.icon-btn:hover {
    background: var(--primary-color);
    color: white;
    transform: translateY(-2px);
}

.mobile-only {
    display: none;
}

@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        top: 70px;
        left: 0;
        right: 0;
        background: var(--bg-color);
        flex-direction: column;
        padding: var(--spacing-lg);
        box-shadow: var(--shadow-lg);
        transform: translateY(-100%);
        opacity: 0;
        visibility: hidden;
        transition: all var(--transition-base);
    }
    
    .nav-menu.active {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }
    
    .mobile-only {
        display: flex;
    }
}

/* ============================================
   HERO SECTION
   ============================================ */
.hero {
    position: relative;
    padding: var(--spacing-2xl) 0;
    overflow: hidden;
    min-height: 600px;
    display: flex;
    align-items: center;
}

.hero-background {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    opacity: 0.05;
    z-index: -1;
}

[data-theme="dark"] .hero-background {
    opacity: 0.1;
}

.hero-content {
    text-align: center;
    max-width: 900px;
    margin: 0 auto;
}

.hero-title {
    font-family: var(--font-heading);
    font-size: clamp(2rem, 5vw, 3.5rem);
    font-weight: 800;
    margin-bottom: var(--spacing-lg);
    line-height: 1.2;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-emoji {
    display: inline-block;
    animation: wave 2s ease-in-out infinite;
}

@keyframes wave {
    0%, 100% { transform: rotate(0deg); }
    25% { transform: rotate(20deg); }
    75% { transform: rotate(-20deg); }
}

.hero-subtitle {
    font-size: clamp(1rem, 2vw, 1.25rem);
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
    line-height: 1.8;
}

.hero-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.stat-card {
    background: var(--bg-color);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    transition: all var(--transition-base);
}

.stat-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.stat-number {
    font-size: 2.5rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-xs);
}

.stat-label {
    color: var(--text-secondary);
    font-size: 0.875rem;
    font-weight: 500;
}

.hero-actions {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* ============================================
   BUTTONS
   ============================================ */
.btn {
    padding: var(--spacing-md) var(--spacing-xl);
    border: none;
    border-radius: var(--radius-lg);
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: all var(--transition-base);
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    text-decoration: none;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    box-shadow: var(--shadow-md);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

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

.btn-secondary:hover {
    background: var(--bg-tertiary);
    transform: translateY(-2px);
}

/* ============================================
   SECTIONS
   ============================================ */
section {
    padding: var(--spacing-2xl) 0;
}

.section-title {
    font-family: var(--font-heading);
    font-size: clamp(1.75rem, 4vw, 2.5rem);
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.title-icon {
    font-size: 1.5em;
}

.section-subtitle {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
    max-width: 800px;
}

/* ============================================
   QUICK NAVIGATION
   ============================================ */
.quick-nav {
    background: var(--bg-secondary);
}

.quick-nav-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-md);
}

.quick-nav-item {
    background: var(--bg-color);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    text-align: center;
    cursor: pointer;
    transition: all var(--transition-base);
    border: 2px solid transparent;
}

.quick-nav-item:hover {
    transform: translateY(-5px);
    border-color: var(--primary-color);
    box-shadow: var(--shadow-lg);
}

.quick-nav-icon {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-sm);
}

.quick-nav-label {
    font-weight: 600;
    color: var(--text-color);
}

.quick-nav-count {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-top: var(--spacing-xs);
}

/* ============================================
   FILTER TABS
   ============================================ */
.filter-tabs {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-xl);
    flex-wrap: wrap;
}

.filter-tab {
    padding: var(--spacing-sm) var(--spacing-lg);
    border: 2px solid var(--border-color);
    background: var(--bg-color);
    border-radius: var(--radius-full);
    cursor: pointer;
    transition: all var(--transition-fast);
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.filter-tab:hover {
    border-color: var(--primary-color);
    background: var(--bg-secondary);
}

.filter-tab.active {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    border-color: transparent;
}

.tab-count {
    background: rgba(255, 255, 255, 0.2);
    padding: 0.125rem 0.5rem;
    border-radius: var(--radius-full);
    font-size: 0.875rem;
}

.filter-tab.active .tab-count {
    background: rgba(255, 255, 255, 0.3);
}

/* ============================================
   CATEGORY GRID
   ============================================ */
.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: var(--spacing-lg);
}

.category-card {
    background: var(--bg-color);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    box-shadow: var(--shadow-md);
    transition: all var(--transition-base);
    cursor: pointer;
    border: 2px solid transparent;
}

.category-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.category-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-md);
}

.category-icon {
    font-size: 2.5rem;
    width: 60px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    border-radius: var(--radius-lg);
}

.category-info h3 {
    font-family: var(--font-heading);
    font-size: 1.25rem;
    margin-bottom: var(--spacing-xs);
}

.category-count {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.category-description {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
    line-height: 1.6;
}

.category-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--border-color);
}

.category-link {
    color: var(--primary-color);
    font-weight: 600;
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

/* ============================================
   CONTROLS BAR
   ============================================ */
.controls-bar {
    display: flex;
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
    flex-wrap: wrap;
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
}

.control-group {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.control-group label {
    font-weight: 600;
    color: var(--text-secondary);
    white-space: nowrap;
}

.control-select {
    padding: var(--spacing-sm) var(--spacing-md);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--bg-color);
    color: var(--text-color);
    font-size: 0.875rem;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.control-select:focus {
    outline: none;
    border-color: var(--primary-color);
}

/* ============================================
   SYSTEMS GRID
   ============================================ */
.systems-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.systems-grid.list-view {
    grid-template-columns: 1fr;
}

.systems-grid.compact-view {
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: var(--spacing-md);
}

.system-card {
    background: var(--bg-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-base);
    cursor: pointer;
    border: 2px solid transparent;
    position: relative;
    overflow: hidden;
}

.system-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    transform: scaleY(0);
    transition: transform var(--transition-base);
}

.system-card:hover::before {
    transform: scaleY(1);
}

.system-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
    border-color: var(--primary-color);
}

.system-card-header {
    display: flex;
    justify-content: space-between;
    align-items: start;
    margin-bottom: var(--spacing-md);
}

.system-id {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-full);
    font-weight: 700;
    font-size: 0.875rem;
}

.system-badge {
    padding: 0.25rem 0.5rem;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 600;
}

.badge-help {
    background: #d4edda;
    color: #155724;
}

.badge-no-help {
    background: #f8d7da;
    color: #721c24;
}

[data-theme="dark"] .badge-help {
    background: #155724;
    color: #d4edda;
}

[data-theme="dark"] .badge-no-help {
    background: #721c24;
    color: #f8d7da;
}

.system-name {
    font-family: var(--font-heading);
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.system-code {
    font-size: 0.875rem;
    color: var(--text-muted);
    font-family: monospace;
}

.system-category {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-full);
    font-size: 0.75rem;
    color: var(--text-secondary);
    margin-top: var(--spacing-sm);
}

/* Compact View Styles */
.systems-grid.compact-view .system-card {
    padding: var(--spacing-md);
}

.systems-grid.compact-view .system-name {
    font-size: 1rem;
}

/* List View Styles */
.systems-grid.list-view .system-card {
    display: flex;
    align-items: center;
    gap: var(--spacing-lg);
}

.systems-grid.list-view .system-card-header {
    margin-bottom: 0;
}

/* ============================================
   PAGINATION
   ============================================ */
.pagination {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
}

.page-btn {
    width: 40px;
    height: 40px;
    border: 2px solid var(--border-color);
    background: var(--bg-color);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    font-weight: 600;
}

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

.page-btn.active {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    border-color: transparent;
}

.page-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* ============================================
   MODAL
   ============================================ */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.7);
    z-index: 9999;
    backdrop-filter: blur(5px);
    animation: fadeIn 0.3s ease;
}

.modal.active {
    display: flex;
    align-items: center;
    justify-content: center;
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

.modal-content {
    background: var(--bg-color);
    border-radius: var(--radius-xl);
    max-width: 800px;
    width: 90%;
    max-height: 90vh;
    overflow: hidden;
    display: flex;
    flex-direction: column;
    animation: slideUp 0.3s ease;
}

@keyframes slideUp {
    from {
        transform: translateY(50px);
        opacity: 0;
    }
    to {
        transform: translateY(0);
        opacity: 1;
    }
}

.modal-header {
    padding: var(--spacing-xl);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: start;
}

.modal-title-group h2 {
    font-family: var(--font-heading);
    font-size: 1.75rem;
    margin-bottom: var(--spacing-sm);
}

.modal-category {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    border-radius: var(--radius-full);
    font-size: 0.875rem;
}

.close-btn {
    width: 40px;
    height: 40px;
    border: none;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    cursor: pointer;
    font-size: 1.5rem;
    transition: all var(--transition-fast);
}

.close-btn:hover {
    background: var(--primary-color);
    color: white;
    transform: rotate(90deg);
}

.modal-body {
    padding: var(--spacing-xl);
    overflow-y: auto;
    flex: 1;
}

.modal-body h3 {
    font-family: var(--font-heading);
    font-size: 1.25rem;
    margin: var(--spacing-lg) 0 var(--spacing-md) 0;
    color: var(--primary-color);
}

.modal-body p {
    margin-bottom: var(--spacing-md);
    line-height: 1.8;
}

.modal-body ul, .modal-body ol {
    margin: var(--spacing-md) 0;
    padding-left: var(--spacing-xl);
}

.modal-body li {
    margin-bottom: var(--spacing-sm);
    line-height: 1.8;
}

.modal-footer {
    padding: var(--spacing-lg) var(--spacing-xl);
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    gap: var(--spacing-md);
}

/* Search Modal */
.search-modal {
    max-width: 600px;
}

.search-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-lg) var(--spacing-xl);
    border-bottom: 1px solid var(--border-color);
}

.search-header h3 {
    font-family: var(--font-heading);
    font-size: 1.5rem;
}

.search-box {
    padding: var(--spacing-lg) var(--spacing-xl);
    position: relative;
}

.search-box input {
    width: 100%;
    padding: var(--spacing-md) var(--spacing-xl) var(--spacing-md) 3rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    font-size: 1rem;
    background: var(--bg-secondary);
    color: var(--text-color);
    transition: all var(--transition-fast);
}

.search-box input:focus {
    outline: none;
    border-color: var(--primary-color);
    background: var(--bg-color);
}

.search-icon {
    position: absolute;
    left: calc(var(--spacing-xl) + var(--spacing-md));
    top: 50%;
    transform: translateY(-50%);
    font-size: 1.25rem;
}

.search-results {
    max-height: 400px;
    overflow-y: auto;
    padding: var(--spacing-md) var(--spacing-xl);
}

.search-placeholder {
    text-align: center;
    padding: var(--spacing-2xl);
    color: var(--text-secondary);
}

.placeholder-icon {
    font-size: 3rem;
    display: block;
    margin-bottom: var(--spacing-md);
}

.placeholder-hint {
    font-size: 0.875rem;
    color: var(--text-muted);
    margin-top: var(--spacing-sm);
}

.search-result-item {
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    margin-bottom: var(--spacing-sm);
}

.search-result-item:hover {
    background: var(--bg-secondary);
}

.search-result-title {
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.search-result-snippet {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.highlight {
    background: yellow;
    color: black;
    padding: 0.125rem 0.25rem;
    border-radius: var(--radius-sm);
}

[data-theme="dark"] .highlight {
    background: #ffd700;
}

/* ============================================
   UPLOAD SECTION
   ============================================ */
.upload-section {
    padding: var(--spacing-xl) 0;
    background: var(--bg-secondary);
}

.upload-card {
    background: var(--bg-color);
    padding: var(--spacing-xl);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
}

.upload-card h3 {
    font-family: var(--font-heading);
    font-size: 1.5rem;
    margin-bottom: var(--spacing-md);
}

.upload-area {
    border: 3px dashed var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-2xl);
    text-align: center;
    cursor: pointer;
    transition: all var(--transition-base);
    margin: var(--spacing-lg) 0;
}

.upload-area:hover {
    border-color: var(--primary-color);
    background: var(--bg-secondary);
}

.upload-area.dragover {
    border-color: var(--primary-color);
    background: var(--bg-secondary);
}

.upload-icon {
    font-size: 3rem;
    display: block;
    margin-bottom: var(--spacing-md);
}

.upload-text {
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

.upload-hint {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.upload-status {
    margin-top: var(--spacing-md);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    display: none;
}

.upload-status.success {
    background: #d4edda;
    color: #155724;
    display: block;
}

.upload-status.error {
    background: #f8d7da;
    color: #721c24;
    display: block;
}

/* ============================================
   ABOUT SECTION
   ============================================ */
.about-section {
    background: var(--bg-secondary);
}

.about-content {
    max-width: 1000px;
    margin: 0 auto;
}

.about-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-2xl);
}

.about-card {
    background: var(--bg-color);
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    text-align: center;
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-base);
}

.about-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
}

.about-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-md);
}

.about-card h3 {
    font-family: var(--font-heading);
    font-size: 1.25rem;
    margin-bottom: var(--spacing-sm);
}

.tech-info, .features-info {
    background: var(--bg-color);
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    margin-bottom: var(--spacing-lg);
}

.tech-info h3, .features-info h3 {
    font-family: var(--font-heading);
    font-size: 1.5rem;
    margin-bottom: var(--spacing-lg);
}

.tech-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
}

.tech-tag {
    padding: var(--spacing-sm) var(--spacing-md);
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    border-radius: var(--radius-full);
    font-size: 0.875rem;
    font-weight: 600;
}

.features-list {
    list-style: none;
    padding: 0;
}

.features-list li {
    padding: var(--spacing-sm) 0;
    border-bottom: 1px solid var(--border-color);
}

.features-list li:last-child {
    border-bottom: none;
}

/* ============================================
   FOOTER
   ============================================ */
.footer {
    background: var(--bg-secondary);
    padding: var(--spacing-2xl) 0 var(--spacing-lg);
    margin-top: var(--spacing-2xl);
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
}

.footer-section h4 {
    font-family: var(--font-heading);
    font-size: 1.125rem;
    margin-bottom: var(--spacing-md);
}

.footer-links {
    list-style: none;
    padding: 0;
}

.footer-links li {
    margin-bottom: var(--spacing-sm);
}

.footer-links a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: color var(--transition-fast);
}

.footer-links a:hover {
    color: var(--primary-color);
}

.footer-bottom {
    text-align: center;
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--border-color);
    color: var(--text-secondary);
}

.footer-note {
    font-size: 0.875rem;
    margin-top: var(--spacing-sm);
}

/* ============================================
   SCROLL TO TOP BUTTON
   ============================================ */
.scroll-top-btn {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 50px;
    height: 50px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    font-size: 1.5rem;
    box-shadow: var(--shadow-lg);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-base);
    z-index: 999;
}

.scroll-top-btn.visible {
    opacity: 1;
    visibility: visible;
}

.scroll-top-btn:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

/* ============================================
   TOAST NOTIFICATION
   ============================================ */
.toast {
    position: fixed;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    background: var(--bg-color);
    padding: var(--spacing-md) var(--spacing-xl);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    z-index: 10000;
    opacity: 0;
    transition: all var(--transition-base);
}

.toast.show {
    transform: translateX(-50%) translateY(0);
    opacity: 1;
}

/* ============================================
   RESPONSIVE DESIGN
   ============================================ */
@media (max-width: 1024px) {
    .hero {
        min-height: 500px;
    }
    
    .category-grid {
        grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    }
    
    .systems-grid {
        grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    }
}

@media (max-width: 768px) {
    html {
        font-size: 14px;
    }
    
    .hero {
        min-height: 400px;
        padding: var(--spacing-xl) 0;
    }
    
    .hero-stats {
        grid-template-columns: 1fr;
    }
    
    .hero-actions {
        flex-direction: column;
        width: 100%;
    }
    
    .hero-actions .btn {
        width: 100%;
        justify-content: center;
    }
    
    .category-grid {
        grid-template-columns: 1fr;
    }
    
    .systems-grid {
        grid-template-columns: 1fr;
    }
    
    .controls-bar {
        flex-direction: column;
        gap: var(--spacing-md);
    }
    
    .control-group {
        width: 100%;
        flex-direction: column;
        align-items: stretch;
    }
    
    .control-select {
        width: 100%;
    }
    
    .modal-content {
        width: 95%;
        max-height: 95vh;
    }
    
    .modal-footer {
        flex-direction: column;
    }
    
    .modal-footer .btn {
        width: 100%;
    }
    
    .scroll-top-btn {
        bottom: 1rem;
        right: 1rem;
        width: 45px;
        height: 45px;
    }
}

@media (max-width: 480px) {
    .section-title {
        font-size: 1.5rem;
    }
    
    .quick-nav-grid {
        grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
    }
    
    .filter-tabs {
        justify-content: center;
    }
    
    .filter-tab {
        font-size: 0.875rem;
        padding: var(--spacing-xs) var(--spacing-md);
    }
}

/* ============================================
   PRINT STYLES
   ============================================ */
@media print {
    .header,
    .hero-actions,
    .controls-bar,
    .pagination,
    .footer,
    .scroll-top-btn,
    .modal,
    .toast,
    .filter-tabs {
        display: none !important;
    }
    
    body {
        background: white;
        color: black;
    }
    
    .system-card,
    .category-card {
        break-inside: avoid;
        box-shadow: none;
        border: 1px solid #ddd;
    }
}

/* ============================================
   ACCESSIBILITY
   ============================================ */
:focus-visible {
    outline: 3px solid var(--primary-color);
    outline-offset: 2px;
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

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

.fade-in-up {
    animation: fadeInUp 0.6s ease;
}

/* ============================================
   UTILITY CLASSES
   ============================================ */
.text-center {
    text-align: center;
}

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

.text-secondary {
    color: var(--text-secondary);
}

.mt-1 { margin-top: var(--spacing-sm); }
.mt-2 { margin-top: var(--spacing-md); }
.mt-3 { margin-top: var(--spacing-lg); }
.mt-4 { margin-top: var(--spacing-xl); }

.mb-1 { margin-bottom: var(--spacing-sm); }
.mb-2 { margin-bottom: var(--spacing-md); }
.mb-3 { margin-bottom: var(--spacing-lg); }
.mb-4 { margin-bottom: var(--spacing-xl); }

.hidden {
    display: none !important;
}

.visible {
    display: block !important;
}