:root {
            --bt74-primary: #4285F4;
            --bt74-success: #34A853;
            --bt74-warning: #FBBC05;
            --bt74-danger: #EA4335;
            --bt74-text: #202124;
            --bt74-text-light: #5f6368;
            --bt74-bg: #ffffff;
            --bt74-bg-soft: #f8f9fa;
            --bt74-glass: rgba(255, 255, 255, 0.85);
            --bt74-radius: 16px;
            --bt74-spacing: 8px;
            --bt74-max-w: 1400px;
        }

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

        body {
            font-family: "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
            color: var(--bt74-text);
            background-color: var(--bt74-bg);
            line-height: 1.6;
            overflow-x: hidden;
            word-break: keep-all;
        }

        /* 导航系统 */
        .bt74-header {
            position: fixed;
            top: 24px;
            left: 50%;
            transform: translateX(-50%);
            width: 95%;
            max-width: 1100px;
            z-index: 1000;
            background: var(--bt74-glass);
            backdrop-filter: blur(12px);
            border-radius: 50px;
            box-shadow: 0 4px 30px rgba(0, 0, 0, 0.08);
            border: 1px solid rgba(255, 255, 255, 0.3);
            padding: 8px 24px;
        }

        .bt74-nav-container {
            display: flex;
            flex-wrap: wrap;
            justify-content: space-between;
            align-items: center;
            min-width: 0;
        }

        .bt74-logo {
            flex: 0 0 auto;
            display: flex;
            align-items: center;
            min-width: 0;
        }

        .bt74-logo img {
            height: 32px;
            width: auto;
        }

        .bt74-nav-list {
            display: flex;
            flex-wrap: wrap;
            list-style: none;
            gap: 16px;
            min-width: 0;
        }

        .bt74-nav-item a {
            text-decoration: none;
            color: var(--bt74-text-light);
            font-size: 0.95rem;
            font-weight: 500;
            padding: 8px 12px;
            border-radius: 20px;
            transition: all 0.3s ease;
            display: inline-block;
            white-space: nowrap;
        }

        .bt74-nav-item a:hover {
            color: var(--bt74-primary);
            background: rgba(66, 133, 244, 0.05);
        }

        .bt74-nav-item.active a {
            color: var(--bt74-primary);
            background: rgba(66, 133, 244, 0.1);
        }

        /* 核心布局 */
        .bt74-main {
            padding-top: 120px;
        }

        .bt74-section {
            padding: 64px 5vw;
            max-width: var(--bt74-max-w);
            margin: 0 auto;
            word-break: break-word;
            overflow-wrap: break-word;
        }

        /* Hero 区块 - 独特非线性设计 */
        .bt74-hero {
            display: flex;
            flex-wrap: wrap;
            align-items: center;
            min-height: 70vh;
            position: relative;
            background: radial-gradient(circle at top right, rgba(66, 133, 244, 0.05), transparent 40%),
                        radial-gradient(circle at bottom left, rgba(52, 168, 83, 0.05), transparent 40%);
        }

        .bt74-hero-content {
            flex: 1 1 500px;
            min-width: 0;
            padding-right: 48px;
        }

        .bt74-hero-title {
            font-size: clamp(2.5rem, 5vw + 1rem, 4.5rem);
            font-weight: 800;
            line-height: 1.1;
            margin-bottom: 24px;
            background: linear-gradient(135deg, #202124 0%, #4285F4 100%);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
        }

        .bt74-hero-subtitle {
            font-size: clamp(1.1rem, 1.5vw + 0.5rem, 1.5rem);
            color: var(--bt74-text-light);
            margin-bottom: 40px;
            max-width: 600px;
        }

        .bt74-hero-visual {
            flex: 1 1 400px;
            min-width: 0;
            display: flex;
            justify-content: center;
            align-items: center;
            position: relative;
        }

        /* 模拟同步感的视觉组件 */
        .bt74-sync-sphere {
            width: 300px;
            height: 300px;
            background: linear-gradient(135deg, var(--bt74-primary), var(--bt74-success));
            border-radius: 38% 62% 63% 37% / 41% 44% 56% 59%;
            filter: blur(40px);
            opacity: 0.2;
            position: absolute;
            animation: bt74-morph 10s infinite alternate ease-in-out;
        }

        @keyframes bt74-morph {
            0% { border-radius: 38% 62% 63% 37% / 41% 44% 56% 59%; }
            100% { border-radius: 63% 37% 30% 70% / 50% 30% 70% 50%; }
        }

        .bt74-floating-card {
            background: var(--bt74-glass);
            padding: 32px;
            border-radius: var(--bt74-radius);
            box-shadow: 0 20px 40px rgba(0,0,0,0.1);
            border: 1px solid rgba(255,255,255,0.5);
            position: relative;
            z-index: 2;
            max-width: 360px;
            transition: transform 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
        }

        .bt74-floating-card:hover {
            transform: translateY(-10px) rotate(2deg);
        }

        /* 功能模块网格 */
        .bt74-features-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
            gap: 32px;
            margin-top: 48px;
        }

        .bt74-feature-card {
            background: var(--bt74-bg-soft);
            padding: 40px;
            border-radius: var(--bt74-radius);
            transition: all 0.3s ease;
            display: flex;
            flex-direction: column;
            min-width: 0;
            border: 1px solid transparent;
        }

        .bt74-feature-card:hover {
            background: white;
            border-color: var(--bt74-primary);
            box-shadow: 0 10px 30px rgba(66, 133, 244, 0.1);
        }

        .bt74-icon-placeholder {
            width: 64px;
            height: 64px;
            background: white;
            border-radius: 12px;
            display: flex;
            align-items: center;
            justify-content: center;
            margin-bottom: 24px;
            box-shadow: 0 4px 12px rgba(0,0,0,0.05);
            font-size: 2rem;
        }

        .bt74-feature-name {
            font-size: 1.5rem;
            font-weight: 700;
            margin-bottom: 16px;
        }

        .bt74-feature-desc {
            color: var(--bt74-text-light);
            font-size: 1rem;
        }

        /* 全平台展示区 */
        .bt74-cross-platform {
            background: var(--bt74-text);
            color: white;
            border-radius: 40px;
            margin: 64px 5vw;
            padding: 80px 64px;
            display: flex;
            flex-wrap: wrap;
            align-items: center;
        }

        .bt74-platform-text {
            flex: 1 1 400px;
            min-width: 0;
        }

        .bt74-platform-text h2 {
            font-size: clamp(2rem, 3vw, 3rem);
            margin-bottom: 24px;
        }

        .bt74-platform-tags {
            display: flex;
            flex-wrap: wrap;
            gap: 12px;
            margin-top: 32px;
        }

        .bt74-tag {
            padding: 8px 20px;
            border: 1px solid rgba(255,255,255,0.2);
            border-radius: 30px;
            font-size: 0.9rem;
        }

        /* 呼吁行动区 */
        .bt74-cta {
            text-align: center;
            background: linear-gradient(rgba(66, 133, 244, 0.05), white);
        }

        .bt74-btn {
            display: inline-block;
            padding: 16px 40px;
            background: var(--bt74-primary);
            color: white;
            text-decoration: none;
            border-radius: 30px;
            font-weight: 600;
            font-size: 1.1rem;
            transition: all 0.3s ease;
            box-shadow: 0 8px 20px rgba(66, 133, 244, 0.3);
        }

        .bt74-btn:hover {
            transform: translateY(-2px);
            box-shadow: 0 12px 24px rgba(66, 133, 244, 0.4);
            background: #3367d6;
        }

        /* 页脚 */
        .bt74-footer {
            padding: 64px 5vw;
            background: var(--bt74-bg-soft);
            border-top: 1px solid rgba(0,0,0,0.05);
        }

        .bt74-footer-grid {
            max-width: var(--bt74-max-w);
            margin: 0 auto;
            display: flex;
            flex-wrap: wrap;
            gap: 48px;
            justify-content: space-between;
        }

        .bt74-footer-brand {
            flex: 1 1 300px;
            min-width: 0;
        }

        .bt74-brand-name {
            font-size: 1.5rem;
            font-weight: 700;
            color: var(--bt74-text);
            margin-bottom: 16px;
        }

        .bt74-footer-links {
            flex: 1 1 200px;
            min-width: 0;
        }

        .bt74-footer-links h4 {
            margin-bottom: 24px;
            font-size: 1.1rem;
        }

        .bt74-footer-links ul {
            list-style: none;
        }

        .bt74-footer-links li {
            margin-bottom: 12px;
        }

        .bt74-footer-links a {
            color: var(--bt74-text-light);
            text-decoration: none;
            transition: color 0.3s;
        }

        .bt74-footer-links a:hover {
            color: var(--bt74-primary);
        }

        .bt74-copyright {
            width: 100%;
            padding-top: 48px;
            margin-top: 48px;
            border-top: 1px solid rgba(0,0,0,0.05);
            text-align: center;
            color: var(--bt74-text-light);
            font-size: 0.9rem;
        }

        /* 响应式调整 */
        @media (max-width: 768px) {
            .bt74-header {
                top: 0;
                width: 100%;
                border-radius: 0;
                padding: 12px;
            }

            .bt74-nav-list {
                display: none; /* 简化移动端，实际开发中应添加汉堡菜单 */
            }

            .bt74-hero {
                padding-top: 60px;
                text-align: center;
            }

            .bt74-hero-content {
                padding-right: 0;
            }

            .bt74-hero-subtitle {
                margin: 0 auto 40px;
            }

            .bt74-cross-platform {
                padding: 48px 24px;
                border-radius: 20px;
            }
        }