:root {
            --bt74-primary: #1a73e8;
            --bt74-primary-dark: #174ea6;
            --bt74-accent-red: #ea4335;
            --bt74-accent-yellow: #fbbc04;
            --bt74-accent-green: #34a853;
            --bt74-text-main: #202124;
            --bt74-text-sub: #5f6368;
            --bt74-bg-light: #f8f9fa;
            --bt74-glass: rgba(255, 255, 255, 0.8);
            --bt74-shadow: 0 10px 30px rgba(0,0,0,0.08);
            --bt74-radius: 20px;
        }

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

        body {
            font-family: 'Segoe UI', Roboto, Helvetica, Arial, "Microsoft YaHei", sans-serif;
            color: var(--bt74-text-main);
            background-color: #ffffff;
            line-height: 1.6;
            overflow-x: hidden;
            word-break: keep-all;
        }

        /* 布局容器 */
        .bt74-container {
            max-width: 1400px;
            margin: 0 auto;
            padding: 0 5vw;
        }

        /* 导航栏设计：悬浮呼吸感 */
        .bt74-header {
            position: fixed;
            top: 20px;
            left: 50%;
            transform: translateX(-50%);
            width: 94vw;
            max-width: 1300px;
            z-index: 1000;
            background: var(--bt74-glass);
            backdrop-filter: blur(15px);
            border: 1px solid rgba(255,255,255,0.3);
            border-radius: 50px;
            box-shadow: var(--bt74-shadow);
            transition: all 0.4s cubic-bezier(0.165, 0.84, 0.44, 1);
        }

        .bt74-nav-container {
            display: flex;
            flex-wrap: wrap;
            align-items: center;
            justify-content: space-between;
            padding: 10px 30px;
            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-menu {
            display: flex;
            flex-wrap: wrap;
            list-style: none;
            gap: 5px;
            min-width: 0;
        }

        .bt74-nav-item {
            min-width: 0;
        }

        .bt74-nav-link {
            text-decoration: none;
            color: var(--bt74-text-sub);
            padding: 8px 16px;
            border-radius: 25px;
            font-size: 14px;
            font-weight: 500;
            transition: all 0.3s ease;
            display: block;
            word-break: break-word;
        }

        .bt74-nav-link:hover {
            background: rgba(26, 115, 232, 0.08);
            color: var(--bt74-primary);
        }

        .bt74-nav-link.active {
            background: var(--bt74-primary);
            color: #fff;
        }

        /* Hero 区：非线性流体布局 */
        .bt74-hero {
            padding-top: 180px;
            padding-bottom: 80px;
            background: radial-gradient(circle at 80% 20%, rgba(26, 115, 232, 0.05) 0%, transparent 40%),
                        radial-gradient(circle at 10% 80%, rgba(52, 168, 83, 0.05) 0%, transparent 40%);
        }

        .bt74-hero-grid {
            display: flex;
            flex-wrap: wrap;
            align-items: center;
            gap: 48px;
            min-width: 0;
        }

        .bt74-hero-text {
            flex: 1;
            min-width: 320px;
            word-break: break-word;
        }

        .bt74-hero-title {
            font-size: clamp(2.5rem, 5vw, 4rem);
            line-height: 1.1;
            font-weight: 800;
            margin-bottom: 24px;
            letter-spacing: -1px;
            color: var(--bt74-text-main);
        }

        .bt74-hero-subtitle {
            font-size: clamp(1.1rem, 2vw, 1.4rem);
            color: var(--bt74-text-sub);
            margin-bottom: 40px;
            max-width: 600px;
        }

        .bt74-hero-image-wrapper {
            flex: 1.2;
            min-width: 320px;
            position: relative;
        }

        .bt74-hero-image {
            width: 100%;
            height: auto;
            border-radius: var(--bt74-radius);
            box-shadow: 0 30px 60px rgba(0,0,0,0.12);
            transition: transform 0.6s cubic-bezier(0.34, 1.56, 0.64, 1);
        }

        .bt74-hero-image:hover {
            transform: scale(1.02) rotate(-1deg);
        }

        /* 核心功能区：卡片式网格 */
        .bt74-section {
            padding: 96px 0;
        }

        .bt74-section-title {
            text-align: center;
            font-size: clamp(2rem, 4vw, 2.8rem);
            margin-bottom: 64px;
        }

        .bt74-features-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
            gap: 32px;
            min-width: 0;
        }

        .bt74-feature-card {
            background: #fff;
            padding: 48px;
            border-radius: var(--bt74-radius);
            border: 1px solid #eee;
            transition: all 0.4s ease;
            display: flex;
            flex-direction: column;
            gap: 20px;
            min-width: 0;
            word-break: break-word;
        }

        .bt74-feature-card:hover {
            border-color: var(--bt74-primary);
            box-shadow: var(--bt74-shadow);
            transform: translateY(-10px);
        }

        .bt74-feature-icon {
            font-size: 40px;
            height: 60px;
            display: flex;
            align-items: center;
        }

        .bt74-feature-name {
            font-size: 1.5rem;
            font-weight: 700;
        }

        .bt74-feature-desc {
            color: var(--bt74-text-sub);
            font-size: 1rem;
            line-height: 1.7;
        }

        /* 图文混排区 */
        .bt74-split-section {
            display: flex;
            flex-wrap: wrap;
            align-items: center;
            gap: 64px;
            margin-bottom: 96px;
            min-width: 0;
        }

        .bt74-split-reverse {
            flex-direction: row-reverse;
        }

        .bt74-split-content {
            flex: 1;
            min-width: 320px;
            word-break: break-word;
        }

        .bt74-split-media {
            flex: 1.2;
            min-width: 320px;
        }

        .bt74-split-media img {
            width: 100%;
            height: auto;
            border-radius: var(--bt74-radius);
            box-shadow: var(--bt74-shadow);
        }

        .bt74-badge {
            display: inline-block;
            padding: 6px 16px;
            background: rgba(26, 115, 232, 0.1);
            color: var(--bt74-primary);
            border-radius: 20px;
            font-weight: 600;
            font-size: 14px;
            margin-bottom: 16px;
        }

        /* 按钮设计 */
        .bt74-btn {
            display: inline-block;
            padding: 16px 40px;
            background: var(--bt74-primary);
            color: #fff;
            text-decoration: none;
            border-radius: 30px;
            font-weight: 600;
            transition: all 0.3s ease;
            border: none;
            cursor: pointer;
            box-shadow: 0 4px 15px rgba(26, 115, 232, 0.3);
        }

        .bt74-btn:hover {
            background: var(--bt74-primary-dark);
            transform: translateY(-2px);
            box-shadow: 0 6px 20px rgba(26, 115, 232, 0.4);
        }

        /* 页脚 */
        .bt74-footer {
            background: var(--bt74-bg-light);
            padding: 80px 0 40px;
            border-top: 1px solid #eee;
        }

        .bt74-footer-grid {
            display: flex;
            flex-wrap: wrap;
            justify-content: space-between;
            gap: 48px;
            margin-bottom: 60px;
            min-width: 0;
        }

        .bt74-footer-brand {
            flex: 1;
            min-width: 200px;
            word-break: break-word;
        }

        .bt74-brand-name {
            font-size: 24px;
            font-weight: 700;
            color: var(--bt74-text-main);
            margin-bottom: 16px;
        }

        .bt74-footer-links {
            display: flex;
            flex-wrap: wrap;
            gap: 64px;
            min-width: 0;
        }

        .bt74-footer-column {
            min-width: 120px;
        }

        .bt74-footer-column h4 {
            margin-bottom: 24px;
            font-size: 16px;
        }

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

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

        .bt74-footer-column a {
            text-decoration: none;
            color: var(--bt74-text-sub);
            font-size: 14px;
            transition: color 0.3s;
        }

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

        .bt74-footer-bottom {
            text-align: center;
            padding-top: 40px;
            border-top: 1px solid #ddd;
            color: var(--bt74-text-sub);
            font-size: 14px;
        }

        /* 响应式调整 */
        @media (max-width: 768px) {
            .bt74-header {
                top: 0;
                width: 100%;
                border-radius: 0;
            }
            .bt74-nav-container {
                padding: 10px 15px;
            }
            .bt74-hero {
                padding-top: 140px;
                text-align: center;
            }
            .bt74-hero-grid {
                flex-direction: column;
            }
            .bt74-hero-subtitle {
                margin: 0 auto 40px;
            }
            .bt74-nav-menu {
                justify-content: center;
                width: 100%;
                margin-top: 10px;
            }
            .bt74-nav-link {
                padding: 6px 10px;
                font-size: 12px;
            }
        }

        /* 动画增强 */
        .bt74-animate-up {
            animation: bt74-fadeUp 0.8s ease-out forwards;
        }

        @keyframes bt74-fadeUp {
            from { transform: translateY(30px); opacity: 0.2; }
            to { transform: translateY(0); opacity: 1; }
        }