* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
        }
        body {
            background: #f0f5fa;
            min-height: 100vh;
            display: flex;
            align-items: center;
            justify-content: center;
            padding: 15px;
        }
        .startup-card {
            max-width: 800px;
            width: 100%;
            background: white;
            border-radius: 30px;
            box-shadow: 0 20px 40px rgba(0,0,0,0.1);
            overflow: hidden;
        }
        .header {
            background: linear-gradient(135deg, #667eea, #764ba2);
            color: white;
            padding: 30px;
            text-align: center;
        }
        .header-icon {
            font-size: 3.5rem;
            margin-bottom: 10px;
        }
        .header h1 {
            font-size: 2.2rem;
            margin-bottom: 5px;
        }
        .header p {
            opacity: 0.9;
            font-size: 1.1rem;
        }
        .content {
            padding: 30px;
        }
        .section-title {
            font-size: 1.5rem;
            margin-bottom: 25px;
            display: flex;
            align-items: center;
            gap: 10px;
            color: #1e293b;
        }
        .section-title i {
            color: #667eea;
            background: #eef2ff;
            padding: 10px;
            border-radius: 15px;
        }
        .device-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(100px, 1fr));
            gap: 15px;
            margin-bottom: 30px;
        }
        .device-card {
            background: #f8fafc;
            border: 2px solid #e2e8f0;
            border-radius: 20px;
            padding: 10px 10px 10px 10px;
            text-align: center;
            cursor: pointer;
            transition: all 0.3s;
        }
        .device-card:hover {
            border-color: #667eea;
            transform: translateY(-3px);
            box-shadow: 0 10px 25px rgba(102,126,234,0.2);
        }
        .device-card.selected {
            border-color: #667eea;
            background: #eef2ff;
        }
        .device-card i {
            font-size: 2.8rem;
            color: #667eea;
            margin-bottom: 10px;
        }
        .device-card h3 {
            font-size: 1.2rem;
            color: #1e293b;
        }
        .version-panel {
            background: #f8fafc;
            border-radius: 20px;
            padding: 20px;
            margin-bottom: 25px;
            border: 2px solid #e2e8f0;
            display: none;
        }
        .version-panel.visible {
            display: block;
            animation: fadeIn 0.3s ease;
        }
        @keyframes fadeIn {
            from { opacity: 0; transform: translateY(-10px); }
            to { opacity: 1; transform: translateY(0); }
        }
        .version-panel h3 {
            margin-bottom: 15px;
            display: flex;
            align-items: center;
            gap: 10px;
            color: #1e293b;
        }
        .version-select {
            width: 100%;
            padding: 15px;
            border: 2px solid #e2e8f0;
            border-radius: 15px;
            font-size: 1rem;
            margin-bottom: 15px;
            background: white;
            cursor: pointer;
        }
        .version-select:focus {
            outline: none;
            border-color: #667eea;
        }
        .info-box {
            background: #eef2ff;
            padding: 15px;
            border-radius: 15px;
            display: flex;
            gap: 12px;
            align-items: flex-start;
        }
        .info-box i {
            color: #667eea;
            font-size: 1.3rem;
        }
        .nav-buttons {
            display: flex;
            justify-content: flex-end;
            margin-top: 30px;
            padding-top: 20px;
            border-top: 2px solid #e2e8f0;
        }
        .btn {
            padding: 14px 35px;
            border: none;
            border-radius: 50px;
            font-weight: 600;
            font-size: 1.1rem;
            cursor: pointer;
            display: inline-flex;
            align-items: center;
            gap: 10px;
            transition: all 0.3s;
        }
        .btn-primary {
            background: linear-gradient(135deg, #667eea, #764ba2);
            color: white;
            box-shadow: 0 10px 20px rgba(102,126,234,0.3);
        }
        .btn-primary:hover:not(:disabled) {
            transform: translateY(-2px);
            box-shadow: 0 15px 25px rgba(102,126,234,0.4);
        }
        .btn-primary:disabled {
            opacity: 0.5;
            cursor: not-allowed;
        }
        .footer-links {
            margin-top: 25px;
            text-align: center;
            padding: 15px;
            background: #f8fafc;
            border-radius: 50px;
        }
        .footer-links a {
            color: #667eea;
            text-decoration: none;
            margin: 0 12px;
            font-size: 0.95rem;
            display: inline-block;
            padding: 5px 0;
        }
        .footer-links a:hover {
            text-decoration: underline;
        }
        .footer-links i {
            margin-right: 5px;
        }
        .wechat-banner {
            background: #1e2b4f;
            color: white;
            padding: 12px 20px;
            border-radius: 50px;
            display: none;
            align-items: center;
            justify-content: space-between;
            margin-bottom: 20px;
            flex-wrap: wrap;
            gap: 10px;
        }
        .wechat-banner.show {
            display: flex;
        }
        .wechat-banner button {
            background: white;
            color: #1e2b4f;
            border: none;
            padding: 8px 20px;
            border-radius: 50px;
            font-weight: 600;
            cursor: pointer;
            display: flex;
            align-items: center;
            gap: 8px;
        }
        @media (max-width: 600px) {
            .device-grid {
                grid-template-columns: repeat(3, 1fr);
            }
            .header h1 {
                font-size: 1.8rem;
            }
            .footer-links a {
                /* display: block; */
                margin: 5px 15px;
            }
        }