:root {
            --bg-primary: #0a0e14;
            --bg-secondary: #111720;
            --bg-card: #161c26;
            --bg-card-alt: #1a2130;
            --bg-elevated: #1e2738;
            --border-subtle: #1e293b;
            --border-medium: #263348;
            --text-primary: #e8ecf2;
            --text-secondary: #b0b8c4;
            --text-tertiary: #7d8a9a;
            --green-bright: #25D366;
            --green-deep: #128C7E;
            --green-glow: rgba(37, 211, 102, 0.18);
            --green-glow-strong: rgba(37, 211, 102, 0.30);
            --radius-sm: 12px;
            --radius-md: 20px;
            --radius-lg: 28px;
            --radius-xl: 36px;
            --transition-fast: 0.18s ease;
            --transition-smooth: 0.28s cubic-bezier(0.4, 0, 0.2, 1);
            --font-stack: system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Helvetica, sans-serif;
        }
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        html {
            scroll-behavior: smooth;
        }
        body {
            font-family: var(--font-stack);
            background-color: var(--bg-primary);
            color: var(--text-primary);
            line-height: 1.6;
            -webkit-font-smoothing: antialiased;
        }
        .container {
            max-width: 1240px;
            margin: 0 auto;
            padding: 0 24px;
        }
        /* HEADER */
        .header {
            background-color: rgba(10, 14, 20, 0.88);
            backdrop-filter: blur(18px);
            -webkit-backdrop-filter: blur(18px);
            border-bottom: 1px solid var(--border-subtle);
            position: sticky;
            top: 0;
            z-index: 100;
        }
        .nav {
            display: flex;
            justify-content: space-between;
            align-items: center;
            flex-wrap: wrap;
            padding: 16px 0;
            gap: 14px;
        }
        .logo {
            font-size: 1.7rem;
            font-weight: 750;
            letter-spacing: -0.025em;
            background: linear-gradient(135deg, #25D366 0%, #34d87a 40%, #128C7E 100%);
            -webkit-background-clip: text;
            background-clip: text;
            color: transparent;
            text-decoration: none;
        }
        .logo-sub {
            font-size: 0.7rem;
            font-weight: 500;
            color: var(--text-tertiary);
            letter-spacing: 0.04em;
            margin-left: 4px;
            vertical-align: super;
            background: none;
            -webkit-background-clip: unset;
            background-clip: unset;
            color: #7d8a9a;
        }
        .nav-links {
            display: flex;
            gap: 28px;
            align-items: center;
            list-style: none;
            flex-wrap: wrap;
        }
        .nav-links a {
            text-decoration: none;
            font-weight: 500;
            color: var(--text-secondary);
            transition: color var(--transition-fast);
            font-size: 0.95rem;
            white-space: nowrap;
        }
        .nav-links a:hover,
        .nav-links .active {
            color: var(--green-bright);
        }
        .nav-links .active {
            font-weight: 650;
        }
        .btn-outline {
            border: 1px solid var(--green-bright);
            background: transparent;
            padding: 8px 20px;
            border-radius: 40px;
            font-weight: 600;
            color: var(--green-bright);
            transition: all var(--transition-fast);
            text-decoration: none;
            cursor: pointer;
            font-size: 0.9rem;
        }
        .btn-outline:hover {
            background: rgba(37, 211, 102, 0.08);
            border-color: #34d87a;
            color: #34d87a;
            box-shadow: 0 0 18px var(--green-glow);
        }
        /* PAGE HERO */
        .page-hero {
            padding: 64px 0 48px;
            background: radial-gradient(ellipse at 30% 30%, rgba(37, 211, 102, 0.06) 0%, transparent 55%),
                        var(--bg-primary);
            border-bottom: 1px solid var(--border-subtle);
            text-align: center;
        }
        .page-hero h1 {
            font-size: clamp(1.9rem, 4vw, 2.8rem);
            font-weight: 800;
            letter-spacing: -0.02em;
            color: #f0f4f8;
            margin-bottom: 16px;
        }
        .page-hero h1 .highlight {
            background: linear-gradient(135deg, #25D366, #5eeea8);
            -webkit-background-clip: text;
            background-clip: text;
            color: transparent;
        }
        .page-hero .lead {
            font-size: 1.15rem;
            color: var(--text-secondary);
            max-width: 720px;
            margin: 0 auto;
            line-height: 1.7;
        }
        /* BUTTONS */
        .btn-primary {
            display: inline-block;
            background: linear-gradient(135deg, #25D366 0%, #1db954 100%);
            color: #0a0e14;
            font-weight: 650;
            padding: 13px 34px;
            border-radius: 44px;
            text-decoration: none;
            transition: all var(--transition-smooth);
            border: none;
            font-size: 1rem;
            cursor: pointer;
            box-shadow: 0 4px 20px rgba(37, 211, 102, 0.22);
        }
        .btn-primary:hover {
            background: linear-gradient(135deg, #34d87a 0%, #25D366 100%);
            box-shadow: 0 8px 32px rgba(37, 211, 102, 0.35);
            transform: translateY(-2px);
        }
        .btn-secondary {
            background: var(--bg-elevated);
            border: 1px solid var(--border-medium);
            padding: 12px 28px;
            border-radius: 40px;
            font-weight: 600;
            text-decoration: none;
            color: var(--text-primary);
            transition: all var(--transition-fast);
            cursor: pointer;
            font-size: 0.95rem;
            display: inline-block;
        }
        .btn-secondary:hover {
            border-color: var(--green-bright);
            background: rgba(37, 211, 102, 0.06);
            box-shadow: 0 0 16px var(--green-glow);
        }
        .section-title {
            font-size: clamp(1.6rem, 3vw, 2rem);
            font-weight: 750;
            margin-bottom: 14px;
            color: #f0f4f8;
            letter-spacing: -0.01em;
        }
        .section-desc {
            color: var(--text-secondary);
            max-width: 680px;
            margin: 0 auto 42px;
            font-size: 1rem;
            line-height: 1.7;
            text-align: center;
        }
        /* CONTENT CARD */
        .content-card {
            background: var(--bg-card);
            border-radius: var(--radius-xl);
            padding: 36px 32px;
            border: 1px solid var(--border-subtle);
            margin-bottom: 32px;
            transition: var(--transition-fast);
        }
        .content-card:hover {
            border-color: rgba(37, 211, 102, 0.25);
            box-shadow: 0 0 24px var(--green-glow);
        }
        .content-card h2 {
            font-size: 1.5rem;
            font-weight: 700;
            margin-bottom: 20px;
            color: #f0f4f8;
            display: flex;
            align-items: center;
            gap: 10px;
        }
        .content-card p, .content-card li {
            color: var(--text-secondary);
            line-height: 1.75;
            margin-bottom: 14px;
        }
        .content-card ul, .content-card ol {
            padding-left: 24px;
            margin-bottom: 16px;
        }
        .content-card li {
            margin-bottom: 8px;
        }
        /* DEVICE SELECT CARDS */
        .device-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 24px;
            margin: 48px 0 32px;
        }
        .device-card {
            background: var(--bg-card);
            border-radius: var(--radius-lg);
            padding: 32px 20px 28px;
            text-align: center;
            border: 1px solid var(--border-subtle);
            transition: all var(--transition-smooth);
            text-decoration: none;
            color: inherit;
            display: block;
        }
        .device-card:hover {
            border-color: rgba(37, 211, 102, 0.45);
            box-shadow: 0 18px 36px -12px rgba(0,0,0,0.5), 0 0 24px var(--green-glow);
            transform: translateY(-6px);
        }
        .device-icon {
            font-size: 2.8rem;
            margin-bottom: 14px;
        }
        .device-card h3 {
            font-weight: 700;
            color: #f0f4f8;
            margin-bottom: 8px;
            font-size: 1.25rem;
        }
        .device-card p {
            color: var(--text-tertiary);
            font-size: 0.9rem;
            line-height: 1.5;
        }
        /* OS DETAIL SECTIONS */
        .os-detail-grid {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 28px;
            margin: 32px 0;
        }
        @media (max-width: 768px) {
            .os-detail-grid {
                grid-template-columns: 1fr;
            }
        }
        .os-panel {
            background: var(--bg-card-alt);
            border-radius: var(--radius-lg);
            padding: 32px 24px;
            border: 1px solid var(--border-subtle);
        }
        .os-panel h3 {
            font-size: 1.3rem;
            font-weight: 700;
            color: #f0f4f8;
            margin-bottom: 18px;
            display: flex;
            align-items: center;
            gap: 8px;
        }
        .step-list {
            counter-reset: step;
            list-style: none;
            padding-left: 0;
        }
        .step-list li {
            counter-increment: step;
            padding: 12px 0 12px 40px;
            position: relative;
            border-bottom: 1px solid var(--border-subtle);
            color: var(--text-secondary);
            font-size: 0.93rem;
        }
        .step-list li:last-child {
            border-bottom: none;
        }
        .step-list li::before {
            content: counter(step);
            position: absolute;
            left: 0;
            top: 10px;
            width: 28px;
            height: 28px;
            border-radius: 50%;
            background: rgba(37, 211, 102, 0.18);
            color: var(--green-bright);
            font-weight: 700;
            font-size: 0.8rem;
            display: flex;
            align-items: center;
            justify-content: center;
        }
        /* SCENARIO CARDS */
        .scenario-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
            gap: 24px;
            margin: 32px 0;
        }
        .scenario-card {
            background: var(--bg-card);
            border-radius: var(--radius-lg);
            padding: 28px 20px;
            border: 1px solid var(--border-subtle);
            transition: var(--transition-smooth);
        }
        .scenario-card:hover {
            border-color: rgba(37, 211, 102, 0.40);
            box-shadow: 0 12px 28px -8px rgba(0,0,0,0.5), 0 0 18px var(--green-glow);
            transform: translateY(-4px);
        }
        .scenario-card h4 {
            font-weight: 700;
            color: #f0f4f8;
            margin-bottom: 8px;
            font-size: 1.1rem;
        }
        .scenario-card p {
            color: var(--text-tertiary);
            font-size: 0.9rem;
            line-height: 1.6;
        }
        /* CTA */
        .cta-section {
            background: linear-gradient(135deg, #111d18 0%, #0f1a15 40%, #0a1410 100%);
            border-radius: var(--radius-xl);
            margin: 40px 0 60px;
            padding: 48px 36px;
            text-align: center;
            border: 1px solid rgba(37, 211, 102, 0.20);
        }
        .cta-section h2 {
            font-size: 1.8rem;
            font-weight: 750;
            margin-bottom: 12px;
            color: #f0f4f8;
        }
        .cta-section p {
            color: var(--text-secondary);
            max-width: 480px;
            margin: 0 auto 24px;
        }
        .cta-buttons {
            display: flex;
            gap: 16px;
            justify-content: center;
            flex-wrap: wrap;
        }
        /* FOOTER */
        .footer {
            border-top: 1px solid var(--border-subtle);
            padding: 44px 0 28px;
            background: var(--bg-secondary);
        }
        .footer-grid {
            display: flex;
            flex-wrap: wrap;
            justify-content: space-between;
            gap: 28px;
            margin-bottom: 32px;
        }
        .footer-col {
            min-width: 130px;
        }
        .footer-col h4 {
            font-weight: 650;
            margin-bottom: 16px;
            color: #d0d8e2;
            font-size: 0.95rem;
        }
        .footer-col ul {
            list-style: none;
        }
        .footer-col li {
            margin-bottom: 10px;
        }
        .footer-col a {
            text-decoration: none;
            color: var(--text-tertiary);
            font-size: 0.84rem;
        }
        .footer-col a:hover {
            color: var(--green-bright);
        }
        .copyright {
            text-align: center;
            padding-top: 24px;
            border-top: 1px solid var(--border-subtle);
            font-size: 0.78rem;
            color: #5a6677;
        }
        @media (max-width: 768px) {
            .nav {
                flex-direction: column;
                gap: 12px;
                align-items: flex-start;
            }
            .nav-links {
                flex-wrap: wrap;
                gap: 16px;
            }
            .cta-section {
                padding: 32px 20px;
            }
            .os-detail-grid {
                grid-template-columns: 1fr;
            }
        }
        @media (max-width: 480px) {
            .cta-buttons {
                flex-direction: column;
                align-items: center;
            }
        }