:root {
            --primary: #1e5a96;
            --primary-light: #3a7cb8;
            --primary-dark: #123d66;
            --accent: #2e9fd8;
            --bg-page: #ffffff;
            --bg-soft: #ffffff;
            --bg-card: #ffffff;
            --gray: #5a6b7c;
            --border: #d0dde8;
            /* Diagram colors */
            --cpu-bg: #7a9cc6;
            --cpu-border: #4a7aa8;
            --mem-bg: #f5d5b8;
            --mem-border: #d4a878;
            --periph-bg: #c5d8ee;
            --periph-border: #8ab4d8;
            --bridge-bg: #f5d5b8;
            --bridge-border: #d4a878;
            --line-color: #4a6a8a;
            --diagram-bg: #ffffff;
            --diagram-border: #d0dde8;
        }
        * { margin: 0; padding: 0; box-sizing: border-box; }
        body {
            font-family: 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
            color: #1a2a3a;
            line-height: 1.6;
            background: var(--bg-page);
        }
        .container { max-width: 1200px; margin: 0 auto; padding: 0 20px; }

        /* Header */
        header {
            background: var(--primary);
            color: #fff;
            padding: 18px 0;
            position: sticky;
            top: 0;
            z-index: 100;
            box-shadow: 0 2px 15px rgba(30,90,150,0.25);
            border-bottom: 3px solid var(--accent);
        }
        header .container {
            display: flex;
            justify-content: space-between;
            align-items: center;
        }
        .logo-text {
            font-size: 1.4rem;
            font-weight: 700;
            color: #fff;
            letter-spacing: 1px;
        }
        .logo-text span { color: #9fd4f5; }
        nav a {
            color: rgba(255,255,255,0.85);
            text-decoration: none;
            margin-left: 28px;
            font-size: 0.9rem;
            font-weight: 500;
            transition: color 0.3s;
            text-transform: uppercase;
            letter-spacing: 0.5px;
        }
        nav a:hover { color: #fff; }

        /* Hero */
        .hero {
            background: linear-gradient(160deg, #e8f2fb 0%, #d4e6f5 50%, #c0daf0 100%);
            padding: 70px 0 60px;
            text-align: center;
            position: relative;
            overflow: hidden;
        }
        .hero::before {
            content: '';
            position: absolute;
            top: -50%;
            right: -20%;
            width: 600px;
            height: 600px;
            background: radial-gradient(circle, rgba(30,90,150,0.06) 0%, transparent 70%);
            border-radius: 50%;
        }
        .hero h1 {
            font-size: 2.6rem;
            color: var(--primary-dark);
            margin-bottom: 12px;
            font-weight: 700;
        }
        .hero h1 span { color: var(--primary); }
        .hero p {
            font-size: 1.15rem;
            color: var(--gray);
            max-width: 780px;
            margin: 0 auto 25px;
        }
        .hero-image {
            max-width: 680px;
            width: 100%;
            margin: 25px auto;
            border-radius: 10px;
            box-shadow: 0 12px 40px rgba(30,90,150,0.18);
            border: 3px solid #fff;
        }
        .hero-badges {
            display: flex;
            justify-content: center;
            gap: 12px;
            flex-wrap: wrap;
            margin-top: 20px;
        }
        .badge {
            background: var(--primary);
            color: #fff;
            padding: 8px 22px;
            border-radius: 4px;
            font-size: 0.85rem;
            font-weight: 600;
            letter-spacing: 0.5px;
            text-transform: uppercase;
            box-shadow: 0 3px 10px rgba(30,90,150,0.2);
        }
        .badge.accent { background: var(--accent); color: #fff; }
        .badge.light { background: #d4e6f5; color: var(--primary-dark); }

        /* Section */
        section { padding: 65px 0; }
        section:nth-child(even) { background: var(--bg-soft); }
        .section-title {
            text-align: center;
            font-size: 2rem;
            color: var(--primary-dark);
            margin-bottom: 8px;
            font-weight: 700;
        }
        .section-title::after {
            content: '';
            display: block;
            width: 60px;
            height: 4px;
            background: var(--accent);
            margin: 12px auto 0;
            border-radius: 2px;
        }
        .section-subtitle {
            text-align: center;
            color: var(--gray);
            margin-bottom: 45px;
            font-size: 1.05rem;
        }

        /* ============================================================ */
        /* BLOCK DIAGRAM - HTML/CSS Redrawn                             */
        /* ============================================================ */
        .diagram-wrapper {
            max-width: 1150px;
            margin: 0 auto;
            background: var(--diagram-bg);
            border-radius: 16px;
            padding: 40px 20px;
            box-shadow: 0 6px 30px rgba(30,90,150,0.08);
            border: 2px solid var(--diagram-border);
            overflow-x: auto;
        }
        .diagram-canvas {
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 0;
            min-width: 950px;
            position: relative;
        }
        /* CPU Center Block */
        .cpu-block {
            background: var(--cpu-bg);
            border: 3px solid var(--cpu-border);
            border-radius: 6px;
            width: 220px;
            min-height: 560px;
            display: flex;
            flex-direction: column;
            justify-content: space-between;
            padding: 20px 0;
            position: relative;
            box-shadow: 0 6px 20px rgba(30,90,150,0.2);
            flex-shrink: 0;
            z-index: 5;
        }
        .cpu-title {
            text-align: center;
            font-size: 1.4rem;
            font-weight: 700;
            color: #fff;
            background: rgba(0,0,0,0.15);
            padding: 8px 0;
            margin: 0 15px 10px;
            border-radius: 4px;
            letter-spacing: 1px;
        }
        .cpu-subtitle {
            text-align: center;
            font-size: 0.75rem;
            color: rgba(255,255,255,0.9);
            margin-bottom: 15px;
            font-weight: 600;
        }
        .cpu-pins {
            display: flex;
            flex-direction: column;
            gap: 6px;
            padding: 0 12px;
        }
        .cpu-pin-row {
            display: flex;
            justify-content: space-between;
            font-size: 0.7rem;
            font-weight: 600;
            color: #1a2a3a;
            padding: 2px 4px;
            border-bottom: 1px dashed rgba(255,255,255,0.3);
        }
        .cpu-pin-row:last-child { border-bottom: none; }
        .cpu-pin-left { text-align: left; }
        .cpu-pin-right { text-align: right; }

        /* Side Columns */
        .side-col {
            display: flex;
            flex-direction: column;
            gap: 16px;
            width: 175px;
            flex-shrink: 0;
        }
        .side-col.left { align-items: flex-end; }
        .side-col.right { align-items: flex-start; }

        /* Nodes */
        .node {
            background: var(--periph-bg);
            border: 2px solid var(--periph-border);
            border-radius: 5px;
            padding: 8px 12px;
            font-size: 0.75rem;
            font-weight: 600;
            color: #1a2a3a;
            text-align: center;
            width: 100%;
            box-shadow: 0 2px 8px rgba(30,90,150,0.08);
            transition: transform 0.2s, box-shadow 0.2s;
            position: relative;
            line-height: 1.3;
        }
        .node:hover {
            transform: translateY(-2px);
            box-shadow: 0 4px 15px rgba(30,90,150,0.18);
        }
        .node.memory {
            background: var(--mem-bg);
            border-color: var(--mem-border);
        }
        .node.bridge {
            background: var(--bridge-bg);
            border-color: var(--bridge-border);
        }
        .node.small { font-size: 0.7rem; padding: 6px 8px; }
        .node.tiny { font-size: 0.65rem; padding: 5px 6px; }

        /* Connector lines */
        .connector-h {
            display: flex;
            align-items: center;
            width: 40px;
            flex-shrink: 0;
        }
        .connector-h .line {
            width: 100%;
            height: 2px;
            background: var(--line-color);
        }
        .connector-h .arrow-left {
            width: 0; height: 0;
            border-top: 5px solid transparent;
            border-bottom: 5px solid transparent;
            border-right: 8px solid var(--line-color);
            flex-shrink: 0;
        }
        .connector-h .arrow-right {
            width: 0; height: 0;
            border-top: 5px solid transparent;
            border-bottom: 5px solid transparent;
            border-left: 8px solid var(--line-color);
            flex-shrink: 0;
        }
        .connector-h .line-wrapper {
            display: flex;
            align-items: center;
            width: 100%;
        }

        /* Middle bridge column */
        .bridge-col {
            display: flex;
            flex-direction: column;
            gap: 12px;
            width: 140px;
            flex-shrink: 0;
            align-items: center;
        }
        .bridge-col .node { width: 100%; }

        /* Right-side sub-structure (for USB hub) */
        .usb-hub-group {
            display: flex;
            flex-direction: column;
            gap: 8px;
            align-items: flex-start;
            width: 100%;
        }
        .usb-hub-group .node { width: 100%; }

        /* Labels on lines */
        .line-label {
            font-size: 0.6rem;
            font-weight: 700;
            color: var(--line-color);
            white-space: nowrap;
            background: #ffffff;
            padding: 0 3px;
            position: absolute;
            top: -14px;
            left: 50%;
            transform: translateX(-50%);
        }
        .connector-h { position: relative; }

        /* Diagram caption */
        .diagram-caption {
            margin-top: 30px;
            color: var(--gray);
            font-size: 0.9rem;
            font-style: italic;
            text-align: center;
            max-width: 1000px;
            margin-left: auto;
            margin-right: auto;
            line-height: 1.5;
        }

        /* ============================================================ */
        /* End Block Diagram                                            */
        /* ============================================================ */

        /* Features Grid */
        .features-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
            gap: 25px;
        }
        .feature-card {
            background: var(--bg-card);
            border-radius: 8px;
            padding: 30px;
            box-shadow: 0 4px 20px rgba(30,90,150,0.07);
            border: 1px solid var(--border);
            border-top: 4px solid var(--primary);
            transition: transform 0.3s, box-shadow 0.3s;
        }
        .feature-card:hover {
            transform: translateY(-6px);
            box-shadow: 0 12px 35px rgba(30,90,150,0.13);
        }
        .feature-card h3 {
            color: var(--primary);
            margin-bottom: 12px;
            font-size: 1.15rem;
            font-weight: 700;
        }
        .feature-card p { color: var(--gray); font-size: 0.95rem; }

        /* Specs Table */
        .specs-table {
            width: 100%;
            border-collapse: collapse;
            background: var(--bg-card);
            border-radius: 8px;
            overflow: hidden;
            box-shadow: 0 4px 20px rgba(30,90,150,0.07);
            border: 1px solid var(--border);
        }
        .specs-table th, .specs-table td {
            padding: 14px 22px;
            text-align: left;
            border-bottom: 1px solid var(--border);
        }
        .specs-table th {
            background: #e8f2fb;
            color: var(--primary-dark);
            font-weight: 600;
            width: 28%;
            font-size: 0.9rem;
            letter-spacing: 0.3px;
            border-right: 2px solid var(--border);
        }
        .specs-table td { font-size: 0.95rem; }
        .specs-table tr:last-child td { border-bottom: none; }
        .specs-table tr:hover { background: #f0f7fd; }

        /* Software Ecosystem */
        .eco-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
            gap: 20px;
        }
        .eco-item {
            background: var(--bg-card);
            border-radius: 8px;
            padding: 22px 24px;
            border-left: 5px solid var(--primary);
            box-shadow: 0 3px 15px rgba(30,90,150,0.06);
            transition: transform 0.3s, box-shadow 0.3s;
            display: flex;
            align-items: flex-start;
            gap: 16px;
        }
        .eco-item:hover {
            transform: translateY(-4px);
            box-shadow: 0 8px 25px rgba(30,90,150,0.12);
            border-left-color: var(--accent);
        }
        .eco-icon {
            font-size: 1.8rem;
            line-height: 1;
            flex-shrink: 0;
            width: 42px;
            height: 42px;
            display: flex;
            align-items: center;
            justify-content: center;
            background: #eaf3fb;
            border-radius: 8px;
            color: var(--primary);
        }
        .eco-content h4 {
            color: var(--primary-dark);
            margin-bottom: 4px;
            font-size: 1rem;
            font-weight: 700;
        }
        .eco-content p {
            color: var(--gray);
            font-size: 0.88rem;
            line-height: 1.5;
        }

        /* CTA */
        .cta {
            background: linear-gradient(135deg, var(--primary-dark) 0%, var(--primary) 100%);
            color: #fff;
            text-align: center;
            padding: 65px 0;
        }
        .cta h2 { font-size: 2rem; margin-bottom: 12px; font-weight: 700; }
        .cta p { color: rgba(255,255,255,0.75); margin-bottom: 28px; font-size: 1.05rem; }
        .btn {
            display: inline-block;
            background: var(--accent);
            color: #fff;
            padding: 15px 45px;
            border-radius: 4px;
            text-decoration: none;
            font-weight: 700;
            font-size: 1rem;
            letter-spacing: 1px;
            text-transform: uppercase;
            transition: background 0.3s, transform 0.3s, box-shadow 0.3s;
            box-shadow: 0 4px 15px rgba(46,159,216,0.4);
        }
        .btn:hover {
            background: #1f8ac0;
            transform: translateY(-2px);
            box-shadow: 0 8px 25px rgba(46,159,216,0.5);
        }

        @media (max-width: 1000px) {
            .diagram-wrapper { padding: 25px 10px; }
            .diagram-canvas { min-width: 900px; }
        }
        @media (max-width: 768px) {
            .hero h1 { font-size: 1.8rem; }
            .hero p { font-size: 1rem; }
            nav { display: none; }
            .specs-table th { width: 38%; font-size: 0.8rem; }
            .specs-table td { font-size: 0.85rem; }
            .eco-item { padding: 18px; }
        }