html {
    box-sizing: border-box;
    scroll-behavior: smooth;
    scroll-padding-top: 80px;
}
*, *::before, *::after {
    box-sizing: inherit;
}

:root {
    --bg-color: #FFFFFF;
    --text-color: #333333;
    --border-color: #E2E8F0;
    --logo-color: #0A0F1E;
    --logo-suffix-color: #3B82F6;
    --nav-color: #4A5568;
    --nav-hover-color: #0A0F1E;
    --input-bg: #FFFFFF;
    --input-border: #CBD5E0;
    --primary-btn-bg: #0A0F1E;
    --primary-btn-color: #FFFFFF;
    --primary-btn-hover: #2D3748;
    --secondary-btn-bg: #3B82F6;
    --secondary-btn-color: #FFFFFF;
    --secondary-btn-hover: #2563EB;
    --hero-h1-color: #0A0F1E;
    --hero-p-color: #4A5568;
    --card-bg: #F7FAFC;
    --card-h3-color: #3B82F6;
    --card-p-color: #4A5568;
    --footer-text-color: #718096;
    --theme-btn-bg: transparent;
    --theme-btn-hover: #E2E8F0;
    --section-alt-bg: #F7FAFC;
    --stat-number-color: #3B82F6;
    --link-color: #3B82F6;
}

body.dark-mode {
    --bg-color: #0A0F1E;
    --text-color: #FFFFFF;
    --border-color: #1A2035;
    --logo-color: #FFFFFF;
    --logo-suffix-color: #79C0FF;
    --nav-color: #A0AEC0;
    --nav-hover-color: #FFFFFF;
    --input-bg: #1A2035;
    --input-border: #2D3748;
    --primary-btn-bg: #FFFFFF;
    --primary-btn-color: #0A0F1E;
    --primary-btn-hover: #E2E8F0;
    --secondary-btn-bg: #3B82F6;
    --secondary-btn-color: #FFFFFF;
    --secondary-btn-hover: #2563EB;
    --hero-h1-color: #FFFFFF;
    --hero-p-color: #A0AEC0;
    --card-bg: #1A2035;
    --card-h3-color: #4A90E2;
    --card-p-color: #A0AEC0;
    --footer-text-color: #A0AEC0;
    --theme-btn-bg: transparent;
    --theme-btn-hover: #2D3748;
    --section-alt-bg: #111827;
    --stat-number-color: #79C0FF;
    --link-color: #79C0FF;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    margin: 0;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

a { color: inherit; text-decoration: none; }

.container {
    width: 90%;
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ── Header ── */
header {
    position: sticky;
    top: 0;
    z-index: 100;
    padding: 16px 0;
    border-bottom: 1px solid var(--border-color);
    background-color: var(--bg-color);
    transition: background-color 0.3s, border-color 0.3s;
}
header .container {
    display: flex;
    align-items: center;
    gap: 30px;
}
.logo {
    font-size: 26px;
    font-weight: 700;
    color: var(--logo-color);
    transition: color 0.3s;
    white-space: nowrap;
}
.logo .logo-suffix {
    color: var(--logo-suffix-color);
    transition: color 0.3s;
}
nav ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    gap: 28px;
}
nav ul li a {
    color: var(--nav-color);
    font-size: 15px;
    font-weight: 500;
    transition: color 0.2s;
}
nav ul li a:hover,
nav ul li a.active {
    color: var(--nav-hover-color);
}
.header-actions {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-left: auto;
}
.lang-select {
    background-color: var(--input-bg);
    color: var(--nav-color);
    border: 1px solid var(--input-border);
    padding: 6px 10px;
    border-radius: 6px;
    font-size: 13px;
    cursor: pointer;
    transition: background-color 0.3s, border-color 0.3s, color 0.3s;
}
.theme-btn {
    background: var(--theme-btn-bg);
    border: none;
    font-size: 18px;
    cursor: pointer;
    padding: 6px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background-color 0.2s;
}
.theme-btn:hover { background-color: var(--theme-btn-hover); }
.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    font-size: 24px;
    color: var(--text-color);
    cursor: pointer;
    padding: 4px 8px;
    margin-left: auto;
}

/* ── Buttons ── */
.primary-btn {
    display: inline-block;
    background-color: var(--primary-btn-bg);
    color: var(--primary-btn-color);
    border: none;
    padding: 10px 22px;
    border-radius: 6px;
    font-size: 15px;
    font-weight: 500;
    cursor: pointer;
    text-align: center;
    transition: background-color 0.2s, color 0.2s;
}
.primary-btn:hover { background-color: var(--primary-btn-hover); }
.secondary-btn {
    display: inline-block;
    background-color: var(--secondary-btn-bg);
    color: var(--secondary-btn-color);
    border: none;
    padding: 12px 26px;
    border-radius: 6px;
    font-size: 15px;
    font-weight: 500;
    cursor: pointer;
    text-align: center;
    transition: background-color 0.2s;
}
.secondary-btn:hover { background-color: var(--secondary-btn-hover); }
.header-cta { font-size: 14px; padding: 8px 16px; }

.text-link {
    font-size: 15px;
    font-weight: 500;
    color: var(--link-color);
    transition: opacity 0.2s;
}
.text-link:hover { opacity: 0.8; }

/* ── Hero ── */
.hero {
    text-align: center;
    padding: 100px 0 80px;
    background-color: var(--bg-color);
    transition: background-color 0.3s;
}
.hero h1 {
    font-size: 44px;
    font-weight: 700;
    margin-bottom: 20px;
    color: var(--hero-h1-color);
    line-height: 1.2;
    transition: color 0.3s;
}
.hero p {
    font-size: 19px;
    color: var(--hero-p-color);
    margin-bottom: 36px;
    max-width: 580px;
    margin-left: auto;
    margin-right: auto;
    transition: color 0.3s;
}
.hero-buttons {
    display: flex;
    gap: 14px;
    justify-content: center;
    flex-wrap: wrap;
}

/* ── Page Hero (sub-pages) ── */
.page-hero {
    padding: 72px 0 48px;
    background-color: var(--bg-color);
    transition: background-color 0.3s;
}
.page-hero h1 {
    font-size: 36px;
    font-weight: 700;
    margin: 0 0 16px;
    color: var(--hero-h1-color);
    transition: color 0.3s;
}
.page-hero .section-desc {
    margin-bottom: 0;
}

/* ── Features Strip ── */
.features {
    padding: 60px 0;
    background-color: var(--bg-color);
    transition: background-color 0.3s;
}
.features .container {
    display: flex;
    gap: 24px;
}
.feature-card {
    background-color: var(--card-bg);
    padding: 28px;
    border-radius: 8px;
    flex: 1;
    transition: background-color 0.3s;
}
.feature-card h3 {
    font-size: 20px;
    font-weight: 600;
    color: var(--card-h3-color);
    margin: 0 0 10px;
    transition: color 0.3s;
}
.feature-card p {
    font-size: 15px;
    color: var(--card-p-color);
    margin: 0;
    line-height: 1.6;
    transition: color 0.3s;
}

/* ── Sections Common ── */
.section-alt {
    background-color: var(--section-alt-bg);
    transition: background-color 0.3s;
}
section {
    padding: 80px 0;
}
section h2 {
    font-size: 32px;
    font-weight: 700;
    margin: 0 0 16px;
    color: var(--hero-h1-color);
    transition: color 0.3s;
}
.section-desc {
    font-size: 16px;
    color: var(--hero-p-color);
    max-width: 640px;
    margin: 0 0 48px;
    line-height: 1.7;
    transition: color 0.3s;
}
.body-text {
    font-size: 16px;
    color: var(--card-p-color);
    max-width: 720px;
    line-height: 1.8;
    margin: 0;
    transition: color 0.3s;
}

/* ── Home Preview Sections ── */
.home-about, .home-tech, .home-solutions, .home-blog {
    padding: 64px 0;
}

/* ── About: Why Grid ── */
.why-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}
.why-card {
    background-color: var(--card-bg);
    padding: 28px;
    border-radius: 8px;
    transition: background-color 0.3s;
}
.why-card h3 {
    font-size: 18px;
    font-weight: 600;
    color: var(--card-h3-color);
    margin: 0 0 10px;
    transition: color 0.3s;
}
.why-card p {
    font-size: 15px;
    color: var(--card-p-color);
    margin: 0;
    line-height: 1.6;
    transition: color 0.3s;
}

/* ── Technology ── */
.tech-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
}
.tech-card {
    background-color: var(--card-bg);
    padding: 32px;
    border-radius: 8px;
    border-left: 3px solid var(--card-h3-color);
    transition: background-color 0.3s;
}
.tech-card h3 {
    font-size: 18px;
    font-weight: 600;
    color: var(--card-h3-color);
    margin: 0 0 10px;
    transition: color 0.3s;
}
.tech-card p {
    font-size: 15px;
    color: var(--card-p-color);
    margin: 0;
    line-height: 1.6;
    transition: color 0.3s;
}

/* ── Technology: Approach ── */
.approach-list {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
}
.approach-item {
    padding: 24px;
    background-color: var(--card-bg);
    border-radius: 8px;
    transition: background-color 0.3s;
}
.approach-item h3 {
    font-size: 16px;
    font-weight: 600;
    color: var(--card-h3-color);
    margin: 0 0 8px;
    transition: color 0.3s;
}
.approach-item p {
    font-size: 14px;
    color: var(--card-p-color);
    margin: 0;
    line-height: 1.6;
    transition: color 0.3s;
}

/* ── Solutions ── */
.solutions-detail {
    display: flex;
    flex-direction: column;
    gap: 24px;
}
.sol-detail-card {
    background-color: var(--bg-color);
    padding: 32px;
    border-radius: 8px;
    transition: background-color 0.3s;
}
.sol-detail-card h3 {
    font-size: 20px;
    font-weight: 600;
    color: var(--card-h3-color);
    margin: 0 0 12px;
    transition: color 0.3s;
}
.sol-detail-card p {
    font-size: 15px;
    color: var(--card-p-color);
    margin: 0 0 16px;
    line-height: 1.6;
    transition: color 0.3s;
}
.sol-features {
    list-style: none;
    padding: 0;
    margin: 0;
}
.sol-features li {
    font-size: 14px;
    color: var(--card-p-color);
    padding: 6px 0;
    padding-left: 16px;
    position: relative;
    transition: color 0.3s;
}
.sol-features li::before {
    content: '\2713';
    position: absolute;
    left: 0;
    color: var(--card-h3-color);
    font-weight: 600;
}
.cta-section {
    text-align: center;
}
.cta-section .section-desc {
    margin-left: auto;
    margin-right: auto;
}

/* ── Blog ── */
.blog-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}
.blog-card {
    background-color: var(--card-bg);
    padding: 28px;
    border-radius: 8px;
    display: flex;
    flex-direction: column;
    transition: background-color 0.3s;
}
.blog-tag {
    display: inline-block;
    font-size: 12px;
    font-weight: 600;
    color: var(--secondary-btn-bg);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 12px;
}
.blog-card h3 {
    font-size: 18px;
    font-weight: 600;
    color: var(--hero-h1-color);
    margin: 0 0 10px;
    transition: color 0.3s;
}
.blog-card p {
    font-size: 14px;
    color: var(--card-p-color);
    margin: 0 0 16px;
    line-height: 1.6;
    flex: 1;
    transition: color 0.3s;
}
.read-more {
    font-size: 14px;
    font-weight: 500;
    color: var(--link-color);
    cursor: pointer;
    transition: color 0.2s;
}
.read-more:hover { opacity: 0.8; }

/* ── Article Reader ── */
.article-reader { display: none; }
.article-reader.active { display: block; }
.back-btn {
    background: none;
    border: none;
    color: var(--link-color);
    font-size: 15px;
    font-weight: 500;
    cursor: pointer;
    padding: 0;
    margin-bottom: 32px;
    transition: color 0.2s;
}
.back-btn:hover { opacity: 0.8; }
.article-full h2 {
    font-size: 28px;
    margin: 12px 0 24px;
}
.article-body {
    max-width: 720px;
    line-height: 1.8;
    font-size: 15px;
    color: var(--text-color);
    transition: color 0.3s;
}
.article-body h3 {
    font-size: 20px;
    font-weight: 600;
    color: var(--hero-h1-color);
    margin: 32px 0 12px;
    transition: color 0.3s;
}
.article-body p {
    margin: 0 0 16px;
    color: var(--card-p-color);
    transition: color 0.3s;
}
.article-body strong {
    color: var(--text-color);
    transition: color 0.3s;
}

/* ── Contact ── */
.contact-wrapper {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: start;
}
.contact-info { padding-top: 8px; }
.contact-item { margin-bottom: 20px; }
.contact-item strong {
    display: block;
    font-size: 13px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--card-p-color);
    margin-bottom: 4px;
    transition: color 0.3s;
}
.contact-item a,
.contact-item span {
    font-size: 16px;
    color: var(--text-color);
    transition: color 0.3s;
}
.contact-item a:hover { color: var(--link-color); }

.reveal-btn {
    background: none;
    border: 1px solid var(--input-border);
    color: var(--link-color);
    padding: 6px 14px;
    border-radius: 6px;
    font-size: 14px;
    cursor: pointer;
    transition: background-color 0.2s, border-color 0.2s;
}
.reveal-btn:hover {
    background-color: var(--card-bg);
}

.contact-form {
    display: flex;
    flex-direction: column;
    gap: 14px;
}
.contact-form input,
.contact-form textarea {
    padding: 12px 14px;
    border: 1px solid var(--input-border);
    border-radius: 6px;
    font-size: 15px;
    font-family: inherit;
    background-color: var(--input-bg);
    color: var(--text-color);
    transition: background-color 0.3s, border-color 0.3s, color 0.3s;
}
.contact-form input:focus,
.contact-form textarea:focus {
    outline: none;
    border-color: var(--secondary-btn-bg);
}
.contact-form textarea {
    resize: vertical;
    min-height: 100px;
}

/* ── Footer ── */
footer {
    border-top: 1px solid var(--border-color);
    background-color: var(--bg-color);
    padding: 48px 0 24px;
    transition: border-color 0.3s, background-color 0.3s;
}
.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 40px;
    margin-bottom: 32px;
}
.footer-brand .logo {
    font-size: 22px;
    display: block;
    margin-bottom: 8px;
}
.footer-brand p {
    font-size: 14px;
    color: var(--footer-text-color);
    margin: 0;
    transition: color 0.3s;
}
.footer-links h4,
.footer-contact-col h4 {
    font-size: 14px;
    font-weight: 600;
    color: var(--text-color);
    margin: 0 0 12px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    transition: color 0.3s;
}
.footer-links a,
.footer-contact-col a {
    display: block;
    font-size: 14px;
    color: var(--footer-text-color);
    margin-bottom: 8px;
    transition: color 0.2s;
}
.footer-links a:hover,
.footer-contact-col a:hover {
    color: var(--link-color);
}
.footer-bottom {
    border-top: 1px solid var(--border-color);
    padding-top: 20px;
    transition: border-color 0.3s;
}
.footer-bottom p {
    font-size: 13px;
    color: var(--footer-text-color);
    margin: 0;
    text-align: center;
    transition: color 0.3s;
}

/* ── Responsive ── */
@media (max-width: 992px) {
    #mainNav {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background-color: var(--bg-color);
        border-bottom: 1px solid var(--border-color);
        padding: 16px 0;
        z-index: 99;
        transition: background-color 0.3s;
    }
    #mainNav.active { display: block; }
    #mainNav ul {
        flex-direction: column;
        gap: 0;
        padding: 0 20px;
    }
    #mainNav ul li a {
        display: block;
        padding: 10px 0;
        font-size: 16px;
    }
    .mobile-menu-btn { display: block; }
    .header-cta { display: none; }

    .hero h1 { font-size: 34px; }
    .hero p { font-size: 17px; }

    .features .container { flex-direction: column; }
    .feature-card { flex: none; }

    .why-grid { grid-template-columns: 1fr; }
    .tech-grid { grid-template-columns: 1fr; }
    .approach-list { grid-template-columns: repeat(2, 1fr); }
    .blog-grid { grid-template-columns: 1fr; }

    .contact-wrapper {
        grid-template-columns: 1fr;
        gap: 40px;
    }
    .footer-grid {
        grid-template-columns: 1fr;
        gap: 24px;
    }
}

@media (max-width: 640px) {
    .container { padding: 0 16px; }
    section { padding: 56px 0; }
    section h2 { font-size: 26px; }
    .section-desc { font-size: 15px; }

    .hero { padding: 64px 0 48px; }
    .hero h1 { font-size: 28px; }
    .hero p { font-size: 16px; }
    .hero-buttons { flex-direction: column; align-items: center; }
    .hero-buttons a { width: 100%; max-width: 280px; }

    .page-hero { padding: 48px 0 32px; }
    .page-hero h1 { font-size: 28px; }

    .approach-list { grid-template-columns: 1fr; }
    .article-full h2 { font-size: 22px; }
}