/* ============================================
   duAI Website — Monochrome Dark Theme
   ============================================ */

:root {
    --bg: #000000;
    --bg-alt: #0a0a0a;
    --fg: #ffffff;
    --fg-soft: #999999;
    --fg-muted: #666666;
    --line: #222222;
    --line-light: #333333;
    --accent: #ffffff;
    --accent-hover: #cccccc;
    --surface: #111111;
    --surface-hover: #1a1a1a;
    --red: #be2323;
    --red-hover: #d22828;
    --radius: 8px;
    --radius-lg: 16px;
    --font: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --mono: 'JetBrains Mono', 'Consolas', monospace;
}

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

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

body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--fg);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

/* ---- NAV ---- */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    background: rgba(0, 0, 0, 0.85);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--line);
}

.nav-inner {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 32px;
    height: 64px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-logo {
    display: flex;
    align-items: center;
    text-decoration: none;
    color: var(--fg);
}

.logo-icon {
    width: 64px;
    height: 28px;
}

.logo-sm {
    width: 48px;
    height: 21px;
}

.nav-links {
    display: flex;
    gap: 32px;
}

.nav-links a {
    text-decoration: none;
    color: var(--fg-soft);
    font-size: 14px;
    font-weight: 500;
    letter-spacing: 0.5px;
    transition: color 0.2s;
}

.nav-links a:hover {
    color: var(--fg);
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 16px;
}

.btn-lang {
    background: none;
    border: 1px solid var(--line-light);
    color: var(--fg-soft);
    padding: 4px 10px;
    border-radius: 4px;
    cursor: pointer;
    font-size: 12px;
    font-weight: 600;
    font-family: var(--mono);
    transition: all 0.2s;
}

.btn-lang:hover {
    border-color: var(--fg);
    color: var(--fg);
}

.nav-github {
    display: flex;
    align-items: center;
    gap: 6px;
    text-decoration: none;
    color: var(--fg-soft);
    font-size: 14px;
    font-weight: 500;
    transition: color 0.2s;
}

.nav-github:hover {
    color: var(--fg);
}

/* ---- HERO ---- */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
    padding: 120px 32px 80px;
}

.hero-bg {
    position: absolute;
    inset: 0;
    background: radial-gradient(ellipse at 50% 30%, rgba(255,255,255,0.03) 0%, transparent 70%);
}

.hero-content {
    max-width: 800px;
    text-align: center;
    position: relative;
    z-index: 1;
}

.hero-badge {
    display: inline-block;
    padding: 6px 16px;
    border: 1px solid var(--line-light);
    border-radius: 100px;
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 2px;
    color: var(--fg-soft);
    margin-bottom: 40px;
}

.hero-title {
    font-size: clamp(64px, 12vw, 140px);
    font-weight: 300;
    line-height: 0.95;
    letter-spacing: -3px;
    margin-bottom: 32px;
}

.hero-title-line {
    display: block;
}

.hero-ai {
    font-weight: 700;
    color: var(--fg);
}

.hero-subtitle {
    font-size: 18px;
    color: var(--fg-soft);
    max-width: 520px;
    margin: 0 auto 48px;
    line-height: 1.7;
    font-weight: 300;
}

.hero-actions {
    display: flex;
    gap: 16px;
    justify-content: center;
    margin-bottom: 64px;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 14px 32px;
    font-size: 14px;
    font-weight: 600;
    letter-spacing: 1px;
    text-decoration: none;
    border-radius: var(--radius);
    cursor: pointer;
    transition: all 0.2s;
    border: none;
    font-family: var(--font);
}

.btn-primary {
    background: var(--fg);
    color: var(--bg);
}

.btn-primary:hover {
    background: var(--accent-hover);
}

.btn-outline {
    background: transparent;
    color: var(--fg);
    border: 1px solid var(--line-light);
}

.btn-outline:hover {
    border-color: var(--fg);
    background: rgba(255,255,255,0.05);
}

.btn-lg {
    padding: 18px 40px;
    font-size: 15px;
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 48px;
}

.stat {
    text-align: center;
}

.stat-value {
    display: block;
    font-size: 28px;
    font-weight: 700;
    font-family: var(--mono);
}

.stat-label {
    font-size: 12px;
    color: var(--fg-muted);
    text-transform: uppercase;
    letter-spacing: 1px;
}

/* ---- SECTIONS ---- */
.section {
    padding: 120px 32px;
}

.section-alt {
    background: var(--bg-alt);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
}

.section-title {
    font-size: clamp(36px, 5vw, 56px);
    font-weight: 300;
    letter-spacing: -1px;
    margin-bottom: 16px;
    text-align: center;
}

.section-subtitle {
    font-size: 17px;
    color: var(--fg-soft);
    text-align: center;
    margin-bottom: 72px;
    font-weight: 300;
}

/* ---- FEATURES ---- */
.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}

.feature-card {
    padding: 40px 32px;
    border: 1px solid var(--line);
    border-radius: var(--radius-lg);
    transition: all 0.3s;
}

.feature-card:hover {
    border-color: var(--line-light);
    background: var(--surface);
}

.feature-icon {
    margin-bottom: 24px;
    color: var(--fg);
}

.feature-card h3 {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 12px;
}

.feature-card p {
    font-size: 14px;
    color: var(--fg-soft);
    line-height: 1.7;
}

/* ---- SCREENSHOTS ---- */
.screenshot-tabs {
    display: flex;
    justify-content: center;
    gap: 8px;
    margin-bottom: 40px;
    flex-wrap: wrap;
}

.screenshot-tab {
    padding: 8px 16px;
    background: transparent;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    color: var(--fg-soft);
    cursor: pointer;
    font-size: 13px;
    font-weight: 500;
    font-family: var(--font);
    transition: all 0.2s;
}

.screenshot-tab:hover {
    border-color: var(--fg);
    color: var(--fg);
}

.screenshot-tab.active {
    background: var(--fg);
    color: var(--bg);
    border-color: var(--fg);
}

.screenshot-display {
    text-align: center;
}

.screenshot-img {
    max-width: 100%;
    max-height: 600px;
    border: 1px solid var(--line);
    border-radius: var(--radius-lg);
    background: var(--surface);
}

/* ---- HOW IT WORKS ---- */
.steps {
    display: flex;
    align-items: flex-start;
    justify-content: center;
    gap: 24px;
}

.step {
    flex: 1;
    max-width: 300px;
    text-align: center;
}

.step-number {
    font-size: 48px;
    font-weight: 700;
    font-family: var(--mono);
    color: var(--line-light);
    margin-bottom: 16px;
}

.step h3 {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 12px;
}

.step p {
    font-size: 14px;
    color: var(--fg-soft);
    line-height: 1.7;
}

.step-arrow {
    font-size: 24px;
    color: var(--fg-muted);
    margin-top: 24px;
}

/* ---- TARGETS ---- */
.targets-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 32px;
}

.target-group h3 {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 16px;
    letter-spacing: 0.5px;
}

.target-list {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.target-tag {
    padding: 6px 12px;
    border: 1px solid var(--line);
    border-radius: 100px;
    font-size: 13px;
    color: var(--fg-soft);
    font-family: var(--mono);
}

/* ---- DOWNLOAD ---- */
.download-card {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 40px;
    border: 1px solid var(--line);
    border-radius: var(--radius-lg);
    margin-bottom: 32px;
}

.download-version {
    display: flex;
    align-items: center;
    gap: 16px;
}

.download-label {
    font-size: 24px;
    font-weight: 700;
    font-family: var(--mono);
}

.download-size {
    font-size: 14px;
    color: var(--fg-muted);
}

.download-requirements {
    display: flex;
    gap: 12px;
    margin-top: 8px;
    font-size: 13px;
    color: var(--fg-muted);
}

.download-alt {
    text-align: center;
}

.download-alt p {
    font-size: 14px;
    color: var(--fg-muted);
    margin-bottom: 12px;
}

.download-code {
    display: inline-block;
    padding: 12px 24px;
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    font-family: var(--mono);
    font-size: 13px;
    color: var(--fg-soft);
}

/* ---- FAQ ---- */
.faq-list {
    max-width: 720px;
    margin: 0 auto;
}

.faq-item {
    border-bottom: 1px solid var(--line);
}

.faq-item summary {
    padding: 24px 0;
    cursor: pointer;
    font-size: 16px;
    font-weight: 500;
    list-style: none;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.faq-item summary::-webkit-details-marker {
    display: none;
}

.faq-item summary::after {
    content: '+';
    font-size: 20px;
    color: var(--fg-muted);
    transition: transform 0.2s;
}

.faq-item[open] summary::after {
    transform: rotate(45deg);
}

.faq-item p {
    padding-bottom: 24px;
    font-size: 14px;
    color: var(--fg-soft);
    line-height: 1.7;
}

/* ---- FOOTER ---- */
.footer {
    padding: 64px 32px;
    border-top: 1px solid var(--line);
}

.footer-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.footer-tagline {
    font-size: 14px;
    color: var(--fg-muted);
    margin-top: 8px;
}

.footer-links {
    display: flex;
    gap: 24px;
}

.footer-links a {
    text-decoration: none;
    color: var(--fg-soft);
    font-size: 14px;
    transition: color 0.2s;
}

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

.footer-copy {
    font-size: 13px;
    color: var(--fg-muted);
}

/* ---- RESPONSIVE ---- */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }

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

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

    .steps {
        flex-direction: column;
        align-items: center;
    }

    .step-arrow {
        transform: rotate(90deg);
        margin: 0;
    }

    .hero-actions {
        flex-direction: column;
        align-items: center;
    }

    .hero-stats {
        flex-wrap: wrap;
        gap: 32px;
    }

    .download-card {
        flex-direction: column;
        gap: 24px;
        text-align: center;
    }

    .footer-inner {
        flex-direction: column;
        gap: 24px;
        text-align: center;
    }
}

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

.fade-up {
    opacity: 0;
    animation: fadeUp 0.6s ease forwards;
}

.fade-up:nth-child(2) { animation-delay: 0.1s; }
.fade-up:nth-child(3) { animation-delay: 0.2s; }
.fade-up:nth-child(4) { animation-delay: 0.3s; }
.fade-up:nth-child(5) { animation-delay: 0.4s; }
.fade-up:nth-child(6) { animation-delay: 0.5s; }