:root {
    --color-primary: #0ea5e9;
    --color-primary-dark: #0284c7;
    --color-primary-light: #38bdf8;
    --color-secondary: #10b981;
    --color-secondary-dark: #059669;
    --color-accent: #f59e0b;
    --color-text: #1f2937;
    --color-text-light: #6b7280;
    --color-text-inverse: #ffffff;
    --color-background: #ffffff;
    --color-background-alt: #f9fafb;
    --color-border: #e5e7eb;
    --color-shadow: rgba(0, 0, 0, 0.1);
    --color-success: #10b981;
    --color-warning: #f59e0b;
    --color-error: #ef4444;

    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;

    --border-radius-sm: 0.375rem;
    --border-radius-md: 0.5rem;
    --border-radius-lg: 0.75rem;
    --border-radius-xl: 1rem;

    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 350ms ease;

    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-weight-normal: 400;
    --font-weight-medium: 500;
    --font-weight-semibold: 600;
    --font-weight-bold: 700;

    --header-height: 72px;
}

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

html {
    scroll-behavior: smooth;
    /* Core Web Vitals optimizations */
    font-display: swap;
}

/* Critical CSS for above-the-fold content */
.critical-content {
    /* Ensure critical content loads first */
    contain: layout style paint;
}

/* Optimize font loading */
@font-face {
    font-family: 'Inter';
    font-style: normal;
    font-weight: 400;
    font-display: swap;
    src: local('Inter Regular'), local('Inter-Regular');
}

body {
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.6;
    color: var(--color-text);
    background-color: var(--color-background);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.site-header {
    position: sticky;
    top: 0;
    z-index: 1000;
    background-color: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--color-border);
    box-shadow: 0 1px 3px var(--color-shadow);
}

.nav-container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

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

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    text-decoration: none;
    color: var(--color-text);
    font-weight: var(--font-weight-bold);
    font-size: 1.25rem;
    transition: color var(--transition-fast);
}

.logo img {
    flex-shrink: 0;
    height: 32px;
    width: auto;
}

.logo:hover {
    color: var(--color-primary);
}

.logo-text {
    white-space: nowrap;
}

.mobile-menu-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-xs);
}

.mobile-menu-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background-color: var(--color-text);
    transition: var(--transition-base);
}

.nav-menu {
    display: flex;
    align-items: center;
    gap: var(--spacing-lg);
}

.nav-links {
    display: flex;
    list-style: none;
    gap: var(--spacing-xs);
    margin: 0;
}

.nav-link {
    display: block;
    padding: var(--spacing-xs) var(--spacing-md);
    text-decoration: none;
    color: var(--color-text);
    font-weight: var(--font-weight-medium);
    border-radius: var(--border-radius-md);
    transition: all var(--transition-fast);
    position: relative;
}

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

.nav-link.active {
    color: var(--color-primary);
    background-color: rgba(14, 165, 233, 0.1);
}

.language-switcher {
    position: relative;
}

.lang-button {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-xs) var(--spacing-md);
    background: none;
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius-md);
    cursor: pointer;
    font-weight: var(--font-weight-medium);
    color: var(--color-text);
    transition: all var(--transition-fast);
}

.lang-button:hover {
    border-color: var(--color-primary);
    color: var(--color-primary);
    background-color: var(--color-background-alt);
}

.lang-dropdown {
    position: absolute;
    top: calc(100% + 8px);
    right: 0;
    min-width: 150px;
    background-color: var(--color-background);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius-md);
    box-shadow: 0 4px 6px -1px var(--color-shadow);
    list-style: none;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: all var(--transition-base);
    z-index: 100;
}

.language-switcher.active .lang-dropdown {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.lang-option {
    display: block;
    padding: var(--spacing-sm) var(--spacing-md);
    text-decoration: none;
    color: var(--color-text);
    transition: all var(--transition-fast);
}

.lang-option:hover {
    background-color: var(--color-background-alt);
    color: var(--color-primary);
}

.lang-option.active {
    color: var(--color-primary);
    font-weight: var(--font-weight-semibold);
}

.main-content {
    min-height: calc(100vh - var(--header-height) - 300px);
}

.hero-section {
    padding: var(--spacing-2xl) var(--spacing-md);
    background: linear-gradient(135deg, #0ea5e9 0%, #06b6d4 100%);
    color: var(--color-text-inverse);
    text-align: center;
}

.hero-container {
    max-width: 1280px;
    margin: 0 auto;
}

.hero-title {
    font-size: 3rem;
    font-weight: var(--font-weight-bold);
    line-height: 1.2;
    margin-bottom: var(--spacing-md);
    animation: fadeInUp 0.6s ease;
}

.hero-subtitle {
    font-size: 1.25rem;
    line-height: 1.5;
    margin-bottom: var(--spacing-xl);
    opacity: 0.95;
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
    animation: fadeInUp 0.6s ease 0.2s both;
}

.hero-actions {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
    animation: fadeInUp 0.6s ease 0.4s both;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-md) var(--spacing-xl);
    font-size: 1rem;
    font-weight: var(--font-weight-semibold);
    text-decoration: none;
    border-radius: var(--border-radius-lg);
    transition: all var(--transition-base);
    cursor: pointer;
    border: none;
    font-family: var(--font-sans);
}

.btn-primary {
    background-color: var(--color-text-inverse);
    color: var(--color-primary);
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

.btn-secondary {
    background-color: rgba(255, 255, 255, 0.2);
    color: var(--color-text-inverse);
    border: 2px solid var(--color-text-inverse);
}

.btn-secondary:hover {
    background-color: var(--color-text-inverse);
    color: var(--color-primary);
}

.btn-outline {
    background-color: transparent;
    color: var(--color-primary);
    border: 2px solid var(--color-primary);
}

.btn-outline:hover {
    background-color: var(--color-primary);
    color: var(--color-text-inverse);
    transform: translateY(-2px);
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

.section {
    padding: var(--spacing-2xl) var(--spacing-md);
}

.section-container {
    max-width: 1280px;
    margin: 0 auto;
}

.section-title {
    font-size: 2.5rem;
    font-weight: var(--font-weight-bold);
    text-align: center;
    margin-bottom: var(--spacing-md);
    color: var(--color-text);
}

.section-subtitle {
    font-size: 1.125rem;
    text-align: center;
    color: var(--color-text-light);
    margin-bottom: var(--spacing-xl);
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
}

.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.card {
    background-color: var(--color-background);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius-xl);
    padding: var(--spacing-xl);
    transition: all var(--transition-base);
    box-shadow: 0 1px 3px var(--color-shadow);
}

.card:hover {
    transform: translateY(-4px);
    box-shadow: 0 10px 25px -5px var(--color-shadow);
    border-color: var(--color-primary);
}

.card-icon {
    width: 48px;
    height: 48px;
    background: linear-gradient(135deg, var(--color-primary), var(--color-primary-light));
    border-radius: var(--border-radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--color-text-inverse);
    margin-bottom: var(--spacing-md);
}

.card-title {
    font-size: 1.5rem;
    font-weight: var(--font-weight-bold);
    margin-bottom: var(--spacing-sm);
    color: var(--color-text);
}

.card-text {
    color: var(--color-text-light);
    line-height: 1.6;
    margin-bottom: var(--spacing-md);
}

.site-footer {
    background-color: var(--color-text);
    color: var(--color-text-inverse);
    padding: var(--spacing-2xl) var(--spacing-md) var(--spacing-lg);
    margin-top: var(--spacing-2xl);
}

.footer-container {
    max-width: 1280px;
    margin: 0 auto;
}

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

.footer-logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-weight: var(--font-weight-bold);
    font-size: 1.25rem;
    margin-bottom: var(--spacing-md);
}

.footer-logo img {
    flex-shrink: 0;
    height: 24px;
    width: auto;
}

.footer-tagline {
    color: rgba(255, 255, 255, 0.8);
    line-height: 1.6;
}

.footer-title {
    font-size: 1.125rem;
    font-weight: var(--font-weight-semibold);
    margin-bottom: var(--spacing-md);
}

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

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

.footer-links a {
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    transition: color var(--transition-fast);
}

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

.footer-text {
    color: rgba(255, 255, 255, 0.8);
    line-height: 1.6;
}

.footer-bottom {
    padding-top: var(--spacing-lg);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    text-align: center;
    color: rgba(255, 255, 255, 0.6);
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@media (max-width: 768px) {
    .mobile-menu-toggle {
        display: flex;
    }

    .nav-menu {
        position: fixed;
        top: var(--header-height);
        left: 0;
        right: 0;
        flex-direction: column;
        background-color: var(--color-background);
        border-bottom: 1px solid var(--color-border);
        padding: var(--spacing-md);
        opacity: 0;
        visibility: hidden;
        transform: translateY(-10px);
        transition: all var(--transition-base);
        box-shadow: 0 4px 6px -1px var(--color-shadow);
    }

    .nav-menu.active {
        opacity: 1;
        visibility: visible;
        transform: translateY(0);
    }

    .nav-links {
        flex-direction: column;
        width: 100%;
    }

    .nav-link {
        width: 100%;
        padding: var(--spacing-md);
    }

    .hero-title {
        font-size: 2rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .section-title {
        font-size: 1.875rem;
    }

    .card-grid {
        grid-template-columns: 1fr;
    }
}

/* Content enrichment images styling */
.content-image-container {
    margin: var(--spacing-lg) 0;
    text-align: center;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

.content-image {
    max-width: 100%;
    max-height: 500px;
    width: auto;
    height: auto;
    border-radius: var(--border-radius-lg);
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    border: 1px solid var(--color-border);
    transition: transform var(--transition-base), box-shadow var(--transition-base);
    object-fit: contain;
}

.content-image:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 15px rgba(0, 0, 0, 0.15);
}

.content-image-caption {
    margin-top: var(--spacing-sm);
    font-size: 0.875rem;
    color: var(--color-text-light);
    font-style: italic;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

/* Specific styling for different image types */
.content-image-container.chart-image {
    max-width: 500px;
}

.content-image-container.chart-image .content-image {
    max-height: 300px;
    background-color: #fafafa;
    padding: var(--spacing-sm);
}

.content-image-container.algorithm-image {
    max-width: 450px;
}

.content-image-container.algorithm-image .content-image {
    max-height: 320px;
}

.content-image-container.solution-image {
    max-width: 500px;
}

.content-image-container.solution-image .content-image {
    max-height: 300px;
}

/* Responsive image containers */
@media (max-width: 768px) {
    .content-image-container {
        margin: var(--spacing-md) 0;
        max-width: 100%;
    }

    .content-image {
        border-radius: var(--border-radius-md);
        max-height: 300px;
    }

    .content-image-container.chart-image .content-image {
        max-height: 250px;
    }

    .content-image-container.algorithm-image .content-image {
        max-height: 280px;
    }

    .content-image-container.solution-image .content-image {
        max-height: 250px;
    }
}

@media (max-width: 480px) {
    .content-image {
        max-height: 200px;
    }

    .content-image-container.chart-image .content-image {
        max-height: 180px;
    }

    .content-image-container.algorithm-image .content-image {
        max-height: 200px;
    }

    .content-image-container.solution-image .content-image {
        max-height: 180px;
    }
}