/* 基础重置与变量 */
        :root {
            --bt74-primary: #4285F4;
            --bt74-red: #EA4335;
            --bt74-yellow: #FBBC05;
            --bt74-green: #34A853;
            --bt74-text: #202124;
            --bt74-text-light: #5f6368;
            --bt74-bg: #ffffff;
            --bt74-glass: rgba(255, 255, 255, 0.8);
            --bt74-spacing-unit: 8px;
            --bt74-container-width: 1300px;
        }

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

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

        /* 导航栏设计 */
        .bt74-header {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            z-index: 1000;
            background: var(--bt74-glass);
            backdrop-filter: blur(12px);
            border-bottom: 1px solid rgba(0,0,0,0.05);
        }

        .bt74-nav-container {
            max-width: var(--bt74-container-width);
            margin: 0 auto;
            padding: 0 24px;
            display: flex;
            flex-wrap: wrap;
            align-items: center;
            justify-content: space-between;
            height: 72px;
        }

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

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

        .bt74-menu {
            display: flex;
            flex-wrap: wrap;
            list-style: none;
            gap: 24px;
            min-width: 0;
        }

        .bt74-menu-item a {
            text-decoration: none;
            color: var(--bt74-text-light);
            font-size: 15px;
            font-weight: 500;
            transition: color 0.3s ease;
            white-space: nowrap;
        }

        .bt74-menu-item a:hover,
        .bt74-menu-item.bt74-active a {
            color: var(--bt74-primary);
        }

        .bt74-menu-item.bt74-active a {
            border-bottom: 2px solid var(--bt74-primary);
            padding-bottom: 4px;
        }

        /* Hero 区块 - 独特非线性流体布局 */
        .bt74-hero-section {
            padding-top: 160px;
            padding-bottom: 96px;
            background: radial-gradient(circle at 90% 10%, rgba(66, 133, 244, 0.05) 0%, transparent 40%),
                        radial-gradient(circle at 10% 90%, rgba(52, 168, 83, 0.05) 0%, transparent 40%);
            position: relative;
            overflow: hidden;
        }

        .bt74-hero-content {
            max-width: var(--bt74-container-width);
            margin: 0 auto;
            padding: 0 24px;
            display: flex;
            flex-wrap: wrap;
            align-items: center;
            gap: 48px;
        }

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

        .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(1rem, 2vw + 0.5rem, 1.4rem);
            color: var(--bt74-text-light);
            margin-bottom: 32px;
            max-width: 600px;
        }

        .bt74-hero-visual {
            flex: 1;
            min-width: 320px;
            position: relative;
            display: flex;
            justify-content: center;
            align-items: center;
        }

        /* 模拟浏览器皮肤层叠感 */
        .bt74-theme-stack {
            width: 100%;
            height: 400px;
            position: relative;
        }

        .bt74-theme-card {
            position: absolute;
            width: 80%;
            height: 240px;
            border-radius: 16px;
            box-shadow: 0 20px 40px rgba(0,0,0,0.1);
            border: 1px solid rgba(255,255,255,0.2);
            transition: transform 0.6s cubic-bezier(0.23, 1, 0.32, 1);
        }

        .bt74-card-1 { background: linear-gradient(45deg, #4285F4, #34A853); top: 0; left: 0; z-index: 3; transform: rotate(-5deg); }
        .bt74-card-2 { background: linear-gradient(45deg, #FBBC05, #EA4335); top: 40px; left: 40px; z-index: 2; transform: rotate(2deg); }
        .bt74-card-3 { background: #f1f3f4; top: 80px; left: 80px; z-index: 1; transform: rotate(8deg); }

        .bt74-theme-stack:hover .bt74-card-1 { transform: translate(-20px, -20px) rotate(-8deg); }
        .bt74-theme-stack:hover .bt74-card-2 { transform: translate(0, 0) rotate(0deg); }
        .bt74-theme-stack:hover .bt74-card-3 { transform: translate(20px, 20px) rotate(12deg); }

        /* 美化馆内容区块 */
        .bt74-themes-grid {
            padding: 96px 0;
            max-width: var(--bt74-container-width);
            margin: 0 auto;
            padding: 0 24px 96px;
        }

        .bt74-section-header {
            margin-bottom: 64px;
            text-align: center;
        }

        .bt74-tag {
            display: inline-block;
            padding: 6px 16px;
            background: rgba(66, 133, 244, 0.1);
            color: var(--bt74-primary);
            border-radius: 20px;
            font-size: 14px;
            font-weight: 600;
            margin-bottom: 16px;
        }

        .bt74-grid-container {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
            gap: 32px;
        }

        .bt74-theme-item {
            background: #fff;
            border-radius: 16px;
            overflow: hidden;
            border: 1px solid #eee;
            transition: all 0.3s ease;
            min-width: 0;
        }

        .bt74-theme-item:hover {
            transform: translateY(-8px);
            box-shadow: 0 12px 24px rgba(0,0,0,0.08);
        }

        .bt74-theme-preview {
            height: 180px;
            width: 100%;
            background-size: cover;
            background-position: center;
        }

        .bt74-theme-info {
            padding: 24px;
            word-break: break-word;
        }

        .bt74-theme-name {
            font-size: 18px;
            font-weight: 700;
            margin-bottom: 8px;
        }

        .bt74-theme-author {
            font-size: 14px;
            color: var(--bt74-text-light);
            margin-bottom: 16px;
        }

        .bt74-btn-apply {
            display: inline-block;
            padding: 10px 24px;
            background: var(--bt74-primary);
            color: white;
            text-decoration: none;
            border-radius: 8px;
            font-weight: 600;
            font-size: 14px;
            transition: opacity 0.3s;
        }

        .bt74-btn-apply:hover {
            opacity: 0.9;
        }

        /* 生产力套件区块 */
        .bt74-accelerator-section {
            background: #f8f9fa;
            padding: 96px 0;
        }

        .bt74-accelerator-container {
            max-width: var(--bt74-container-width);
            margin: 0 auto;
            padding: 0 24px;
            display: flex;
            flex-wrap: wrap;
            gap: 32px;
        }

        .bt74-acc-card {
            flex: 1;
            min-width: 300px;
            background: white;
            padding: 40px;
            border-radius: 24px;
            display: flex;
            flex-direction: column;
            gap: 16px;
            box-shadow: 0 4px 6px rgba(0,0,0,0.02);
            transition: transform 0.3s ease;
            word-break: break-word;
        }

        .bt74-acc-card:hover {
            transform: translateY(-5px);
        }

        .bt74-acc-icon {
            width: 48px;
            height: 48px;
            border-radius: 12px;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 24px;
            margin-bottom: 8px;
        }

        .bt74-acc-title {
            font-size: 22px;
            font-weight: 700;
        }

        .bt74-acc-desc {
            color: var(--bt74-text-light);
            font-size: 16px;
            line-height: 1.7;
        }

        .bt74-acc-target {
            margin-top: auto;
            font-size: 13px;
            font-weight: 600;
            text-transform: uppercase;
            letter-spacing: 1px;
            color: var(--bt74-primary);
        }

        /* 动态内容区块 */
        .bt74-dynamic-news {
            padding: 96px 24px;
            max-width: 900px;
            margin: 0 auto;
        }

        .bt74-news-item {
            display: flex;
            flex-wrap: wrap;
            gap: 24px;
            margin-bottom: 48px;
            align-items: flex-start;
        }

        .bt74-news-date {
            font-weight: 700;
            color: var(--bt74-red);
            font-size: 14px;
            width: 80px;
        }

        .bt74-news-body {
            flex: 1;
            min-width: 0;
        }

        .bt74-news-title {
            font-size: 20px;
            font-weight: 700;
            margin-bottom: 12px;
        }

        /* 页脚 */
        .bt74-footer {
            background: #202124;
            color: white;
            padding: 80px 24px;
        }

        .bt74-footer-grid {
            max-width: var(--bt74-container-width);
            margin: 0 auto;
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 48px;
        }

        .bt74-footer-brand {
            font-size: 24px;
            font-weight: 700;
            margin-bottom: 16px;
        }

        .bt74-footer-links h4 {
            margin-bottom: 24px;
            font-size: 16px;
            color: #9aa0a6;
        }

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

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

        .bt74-footer-links a {
            color: #e8eaed;
            text-decoration: none;
            font-size: 14px;
            transition: color 0.3s;
        }

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

        .bt74-copyright {
            max-width: var(--bt74-container-width);
            margin: 48px auto 0;
            padding-top: 32px;
            border-top: 1px solid #3c4043;
            font-size: 13px;
            color: #9aa0a6;
            text-align: center;
        }

        /* 响应式调整 */
        @media (max-width: 768px) {
            .bt74-nav-container {
                height: auto;
                padding: 16px;
            }
            .bt74-menu {
                margin-top: 16px;
                gap: 12px;
                justify-content: center;
            }
            .bt74-hero-section {
                padding-top: 120px;
            }
            .bt74-hero-visual {
                display: none; /* 移动端简化 */
            }
            .bt74-hero-text {
                text-align: center;
            }
        }