:root {
    --primary-color: #2C2E3B;
    --primary-light: #3A3D4F;
    --primary-dark: #1F2029;
    --accent-color: #6366F1;
    --accent-light: #818CF8;
    --success-color: #10B981;
    --warning-color: #F59E0B;
    --error-color: #EF4444;
    --text-primary: #FFFFFF;
    --text-secondary: #B0B7C3;
    --text-muted: #8B92A5;
    --background: #0F1017;
    --surface: #1A1D26;
    --surface-hover: #212530;
    --border: #2D3142;
    --glass-bg: rgba(255, 255, 255, 0.05);
    --glass-border: rgba(255, 255, 255, 0.1);
    --shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 16px 64px rgba(0, 0, 0, 0.5);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', sans-serif;
    background: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
    min-width: 320px;
    -webkit-text-size-adjust: 100%;
    -ms-text-size-adjust: 100%;
}

/* Glass morphism effect */
.glass {
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    border: 1px solid var(--glass-border);
    border-radius: 16px;
}

.glass-strong {
    background: rgba(255, 255, 255, 0.08);
    backdrop-filter: blur(30px);
    border: 1px solid rgba(255, 255, 255, 0.15);
}

/* Header and Navigation */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    padding: 1rem 2rem;
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--glass-border);
    min-height: 80px;
    box-sizing: border-box;
}

.nav-container {
    display: flex;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
    gap: 1rem;
    min-height: 48px;
    flex-wrap: nowrap;
    overflow-x: auto;
}

.back-nav {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-secondary);
    text-decoration: none;
    padding: 0.5rem 1rem;
    border-radius: 8px;
    transition: all 0.3s ease;
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    flex-shrink: 0;
}

.back-nav:hover {
    color: var(--text-primary);
    background: var(--surface-hover);
    transform: translateY(-2px);
}

.logo {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--accent-color);
    text-decoration: none;
    white-space: nowrap;
    flex-shrink: 0;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 1.5rem;
    margin-left: auto;
    flex-wrap: nowrap;
    overflow-x: auto;
    white-space: nowrap;
}

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: all 0.3s ease;
    padding: 0.5rem 1rem;
    border-radius: 8px;
    white-space: nowrap;
    flex-shrink: 0;
}

.nav-link:hover,
.nav-link.active {
    color: var(--text-primary);
    background: var(--glass-bg);
}

/* Progress Bar */
.progress-container {
    position: fixed;
    top: 80px;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--surface);
    z-index: 999;
}

.progress-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--accent-color), var(--accent-light));
    width: 0%;
    transition: width 0.3s ease;
}

/* Main Content */
.main-content {
    margin-top: 120px;
    max-width: 1200px;
    margin-left: auto;
    margin-right: auto;
    padding: 0 2rem;
}

/* Hero Section */
.hero {
    text-align: center;
    padding: 4rem 2rem 6rem;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    margin: 0 0 4rem;
    border-radius: 16px;
}

.hero h1 {
    font-size: 3.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
    background: linear-gradient(135deg, var(--text-primary), var(--accent-light));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto 2rem;
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 3rem;
    margin-top: 3rem;
}

.stat {
    text-align: center;
}

.stat-number {
    font-size: 2rem;
    font-weight: 700;
    color: var(--accent-color);
}

.stat-label {
    font-size: 0.875rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* Section Styles */
.section {
    margin-bottom: 4rem;
    scroll-margin-top: 140px;
}

.section-header {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 2rem;
    padding: 1.5rem 2rem;
    background: var(--surface);
    border-radius: 16px;
    border-left: 4px solid var(--accent-color);
}

.section-icon {
    font-size: 2rem;
    color: var(--accent-color);
}

.section-title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
}

.section-subtitle {
    color: var(--text-secondary);
    font-size: 1rem;
    margin-left: auto;
}

/* Subsection Grid */
.subsections {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 1.5rem;
}

.subsection {
    padding: 1.5rem;
    background: var(--surface);
    border-radius: 12px;
    border: 1px solid var(--border);
    transition: all 0.3s ease;
    cursor: pointer;
}

.subsection:hover {
    transform: translateY(-2px);
    background: var(--surface-hover);
    border-color: var(--accent-color);
    box-shadow: var(--shadow);
}

.subsection-header {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 1rem;
}

.subsection-icon {
    color: var(--accent-color);
    font-size: 1.25rem;
}

.subsection-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
}

.subsection-content {
    color: var(--text-secondary);
    line-height: 1.6;
}

.subsection-content ul {
    margin: 0.5rem 0;
    padding-left: 1rem;
}

.subsection-content li {
    margin: 0.25rem 0;
}

/* Special Cards */
.feature-card {
    background: linear-gradient(135deg, var(--accent-color), var(--accent-light));
    color: white;
    padding: 2rem;
    border-radius: 16px;
    margin: 2rem 0;
}

.feature-card h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

.tip-card {
    background: var(--glass-bg);
    border: 1px solid var(--success-color);
    border-radius: 12px;
    padding: 1rem;
    margin: 1rem 0;
}

.tip-card::before {
    content: "💡";
    margin-right: 0.5rem;
}

/* Code Blocks */
.code-block {
    background: var(--primary-dark);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 1rem;
    margin: 1rem 0;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.875rem;
    overflow-x: auto;
}

/* Responsive Design */
@media (min-width: 769px) and (max-width: 1024px) {
    .subsections {
        grid-template-columns: repeat(2, 1fr);
        gap: 1.5rem;
    }
    
    .nav-menu {
        gap: 1.5rem;
    }
}




/* Keyboard Navigation Highlight */
.keyboard-focus {
    outline: 2px solid var(--accent-color);
    outline-offset: 2px;
}

/* Animation Classes */
.fade-in {
    animation: fadeIn 0.6s ease-out;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.slide-in-left {
    animation: slideInLeft 0.6s ease-out;
}

@keyframes slideInLeft {
    from {
        opacity: 0;
        transform: translateX(-30px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes slideInFromTop {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Mobile Menu Toggle Button */
.mobile-menu-toggle {
    display: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    width: 44px;
    height: 44px;
    background: transparent;
    border: none;
    cursor: pointer;
    padding: 8px;
    border-radius: 8px;
    transition: background-color 0.3s ease;
    position: relative;
    z-index: 1001;
}

.mobile-menu-toggle:hover {
    background: rgba(255, 255, 255, 0.1);
}

.hamburger-line {
    display: block;
    width: 24px;
    height: 3px;
    background: var(--text-primary);
    margin: 3px 0;
    transition: all 0.3s ease;
    border-radius: 2px;
}

/* Hamburger animation */
.mobile-menu-toggle.active .hamburger-line:nth-child(1) {
    transform: rotate(45deg) translate(6px, 6px);
    background: var(--accent-color);
}

.mobile-menu-toggle.active .hamburger-line:nth-child(2) {
    opacity: 0;
    transform: scale(0);
}

.mobile-menu-toggle.active .hamburger-line:nth-child(3) {
    transform: rotate(-45deg) translate(6px, -6px);
    background: var(--accent-color);
}

.mobile-menu-toggle.active {
    background: rgba(99, 102, 241, 0.1) !important;
    border-radius: 50% !important;
}

/* Mobile Responsive Design */
@media screen and (max-width: 768px) {
    /* Header adjustments - fixed positioning */
    .header {
        position: fixed !important;
        padding: 0.8rem 1rem !important;
        min-height: 70px !important;
        backdrop-filter: blur(20px) !important;
        background: rgba(15, 16, 23, 0.95) !important;
        border-bottom: 1px solid var(--border) !important;
    }
    
    /* Navigation container - responsive layout */
    .nav-container {
        display: flex !important;
        justify-content: space-between !important;
        align-items: center !important;
        max-width: 100% !important;
        gap: 0.5rem !important;
        position: relative !important;
        min-height: 54px !important;
    }
    
    /* Back navigation - optimized */
    .back-nav {
        font-size: 0.85rem !important;
        padding: 0.5rem 0.8rem !important;
        white-space: nowrap !important;
        flex-shrink: 0 !important;
    }
    
    .back-nav .material-icons {
        font-size: 18px !important;
    }
    
    /* Logo positioning - centered */
    .logo {
        font-size: 1.1rem !important;
        text-align: center !important;
        flex: 1 !important;
        min-width: 0 !important;
        overflow: hidden !important;
        text-overflow: ellipsis !important;
        white-space: nowrap !important;
    }
    
    /* Show mobile menu toggle */
    .mobile-menu-toggle {
        display: flex !important;
        flex-shrink: 0 !important;
        width: 40px !important;
        height: 40px !important;
    }
    
    /* Navigation menu - mobile dropdown */
    .nav-menu {
        position: fixed !important;
        top: 70px !important;
        left: 0 !important;
        right: 0 !important;
        width: 100vw !important;
        background: rgba(26, 29, 38, 0.98) !important;
        backdrop-filter: blur(30px) !important;
        border: none !important;
        border-top: 1px solid var(--border) !important;
        flex-direction: column !important;
        padding: 1.5rem 0 !important;
        margin: 0 !important;
        transform: translateY(-100%) !important;
        opacity: 0 !important;
        visibility: hidden !important;
        transition: all 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94) !important;
        z-index: 998 !important;
        box-shadow: 0 8px 25px rgba(0, 0, 0, 0.4) !important;
        max-height: calc(100vh - 70px) !important;
        overflow-y: auto !important;
    }
    
    /* Show menu when active */
    .nav-menu.active {
        transform: translateY(0) !important;
        opacity: 1 !important;
        visibility: visible !important;
    }
    
    /* Navigation links in dropdown */
    .nav-link {
        display: block !important;
        padding: 1rem 1.5rem !important;
        font-size: 1rem !important;
        font-weight: 500 !important;
        text-decoration: none !important;
        color: var(--text-secondary) !important;
        border-bottom: 1px solid rgba(255, 255, 255, 0.05) !important;
        transition: all 0.3s ease !important;
        position: relative !important;
        margin: 0 !important;
        min-height: 54px !important;
        display: flex !important;
        align-items: center !important;
    }
    
    .nav-link:last-child {
        border-bottom: none !important;
    }
    
    .nav-link:hover,
    .nav-link.active {
        background: rgba(99, 102, 241, 0.1) !important;
        color: var(--text-primary) !important;
        padding-left: 2rem !important;
    }
    
    .nav-link:active {
        background: rgba(99, 102, 241, 0.2) !important;
    }
    
    /* Progress bar positioning */
    .progress-container {
        top: 70px !important;
    }
    
    /* Main content spacing */
    .main-content {
        margin-top: 85px !important;
        padding: 0 1rem !important;
        max-width: 100% !important;
    }
    
    /* Hero section */
    .hero {
        padding: 2rem 1rem 2.5rem !important;
        margin: 0 0 2rem !important;
        border-radius: 16px !important;
    }
    
    .hero h1 {
        font-size: 2rem !important;
        line-height: 1.2 !important;
        margin-bottom: 1rem !important;
        word-wrap: break-word !important;
    }
    
    .hero-subtitle {
        font-size: 1rem !important;
        max-width: 100% !important;
        margin: 0 auto 1.5rem !important;
        line-height: 1.5 !important;
        padding: 0 0.5rem !important;
    }
    
    /* Hero stats - responsive grid */
    .hero-stats {
        display: grid !important;
        grid-template-columns: repeat(3, 1fr) !important;
        gap: 0.8rem !important;
        margin-top: 1.5rem !important;
        justify-items: center !important;
    }
    
    .stat {
        min-width: 0 !important;
    }
    
    .stat-number {
        font-size: 1.5rem !important;
    }
    
    .stat-label {
        font-size: 0.75rem !important;
        text-align: center !important;
    }
    
    /* Grid layouts */
    .subsections {
        grid-template-columns: 1fr !important;
        gap: 1rem !important;
    }
    
    .subsection {
        padding: 1.2rem !important;
    }
    
    /* Section headers */
    .section-header {
        flex-direction: row !important;
        flex-wrap: wrap !important;
        text-align: left !important;
        padding: 1.2rem !important;
        gap: 0.8rem !important;
        align-items: center !important;
    }
    
    .section-title {
        font-size: 1.6rem !important;
        flex: 1 1 auto !important;
        min-width: 0 !important;
    }
    
    .section-subtitle {
        margin-left: 0 !important;
        margin-top: 0 !important;
        flex-basis: 100% !important;
        order: 3 !important;
    }
}

@media screen and (max-width: 480px) {
    /* Compact header */
    .header {
        padding: 0.6rem 0.8rem !important;
        min-height: 65px !important;
    }
    
    .nav-container {
        min-height: 50px !important;
    }
    
    .back-nav {
        font-size: 0.8rem !important;
        padding: 0.4rem 0.6rem !important;
    }
    
    .logo {
        font-size: 1rem !important;
    }
    
    .mobile-menu-toggle {
        width: 36px !important;
        height: 36px !important;
    }
    
    /* Navigation menu positioning */
    .nav-menu {
        top: 65px !important;
        padding: 1rem 0 !important;
    }
    
    .nav-link {
        padding: 0.8rem 1rem !important;
        font-size: 0.9rem !important;
        min-height: 48px !important;
    }
    
    /* Progress bar */
    .progress-container {
        top: 65px !important;
    }
    
    /* Main content */
    .main-content {
        margin-top: 75px !important;
        padding: 0 0.8rem !important;
    }
    
    /* Compact hero for small screens */
    .hero {
        padding: 1.5rem 0.8rem 2rem !important;
        margin: 0 0 1.5rem !important;
    }
    
    .hero h1 {
        font-size: 1.8rem !important;
        line-height: 1.2 !important;
    }
    
    .hero-subtitle {
        font-size: 0.95rem !important;
        padding: 0 0.2rem !important;
    }
    
    /* Hero stats - vertical on very small screens */
    .hero-stats {
        grid-template-columns: 1fr !important;
        gap: 0.8rem !important;
        margin-top: 1.2rem !important;
    }
    
    /* Section adjustments */
    .section-header {
        padding: 1rem !important;
    }
    
    .section-title {
        font-size: 1.4rem !important;
    }
    
    .subsection {
        padding: 1rem !important;
    }
}

@media screen and (max-width: 360px) {
    /* Ultra-compact layout */
    .header {
        padding: 0.5rem 0.6rem !important;
        min-height: 60px !important;
    }
    
    .nav-container {
        min-height: 48px !important;
        gap: 0.3rem !important;
    }
    
    .back-nav {
        font-size: 0.75rem !important;
        padding: 0.3rem 0.5rem !important;
    }
    
    .logo {
        font-size: 0.95rem !important;
    }
    
    .mobile-menu-toggle {
        width: 32px !important;
        height: 32px !important;
    }
    
    .hamburger-line {
        width: 20px !important;
        height: 2px !important;
    }
    
    /* Navigation menu */
    .nav-menu {
        top: 60px !important;
    }
    
    .nav-link {
        padding: 0.7rem 0.8rem !important;
        font-size: 0.85rem !important;
        min-height: 44px !important;
    }
    
    /* Progress bar */
    .progress-container {
        top: 60px !important;
    }
    
    /* Main content */
    .main-content {
        margin-top: 70px !important;
        padding: 0 0.6rem !important;
    }
    
    /* Hero */
    .hero {
        padding: 1.2rem 0.6rem 1.5rem !important;
        margin: 0 0 1.2rem !important;
    }
    
    .hero h1 {
        font-size: 1.6rem !important;
        line-height: 1.1 !important;
    }
    
    .hero-subtitle {
        font-size: 0.9rem !important;
        padding: 0 !important;
    }
    
    /* Sections */
    .section-header {
        padding: 0.8rem !important;
    }
    
    .section-title {
        font-size: 1.3rem !important;
    }
    
    .subsection {
        padding: 0.8rem !important;
    }
    
    .subsection-content {
        font-size: 0.9rem !important;
    }
}

/* Touch device optimizations */
@media (hover: none) {
    .back-nav:hover,
    .nav-link:hover {
        transform: none;
    }
}

/* Loading Animation */
.loading {
    position: relative;
    overflow: hidden;
}

.loading::after {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.1), transparent);
    animation: loading 1.5s infinite;
}

@keyframes loading {
    0% {
        left: -100%;
    }
    100% {
        left: 100%;
    }
}