:root {
            --primary-blue: #0066ff;
            --soft-blue: #f0f7ff;
            --bg-gray: #f8f9fa;
            --border-color: #e9ecef;
            --text-dark: #212529;
            --text-muted: #6c757d;
            --page-width: 1100px;
        }

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

        body {
            font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
            background-color: var(--bg-gray);
            color: var(--text-dark);
            line-height: 1.6;
        }

        /* 固定导航栏 */
        .navbar {
            position: fixed;
            top: 0;
            width: 100%;
            background: rgba(255, 255, 255, 0.9);
            backdrop-filter: blur(10px);
            border-bottom: 1px solid var(--border-color);
            z-index: 1000;
        }

        .navbar-inner {
            max-width: var(--page-width);
            margin: 0 auto;
            height: 60px;
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 0 20px;
        }

        .logo {
            font-size: 20px;
            font-weight: 700;
            color: var(--primary-blue);
            text-decoration: none;
        }

        .nav-links a {
            text-decoration: none;
            color: var(--text-dark);
            font-size: 14px;
            margin-left: 25px;
            font-weight: 500;
            transition: color 0.2s;
        }

        .nav-links a:hover { color: var(--primary-blue); }

        /* 主容器 */
        .container {
            max-width: var(--page-width);
            margin: 90px auto 60px;
            padding: 0 20px;
        }

        /* 顶部标题区 */
        .page-header {
            background: #fff;
            padding: 40px;
            border-radius: 16px;
            border: 1px solid var(--border-color);
            margin-bottom: 30px;
        }

        .page-header h1 {
            font-size: 32px;
            margin-bottom: 10px;
            color: var(--text-dark);
        }

        .page-header p {
            color: var(--text-muted);
            font-size: 16px;
        }

        /* 知识点区块 */
        .section-card {
            background: #fff;
            padding: 30px;
            border-radius: 16px;
            border: 1px solid var(--border-color);
            margin-bottom: 30px;
        }

        .section-title {
            font-size: 20px;
            font-weight: 700;
            margin-bottom: 25px;
            padding-left: 12px;
            border-left: 4px solid var(--primary-blue);
        }

        /* 积木介绍列表 */
        .block-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
            gap: 20px;
        }

        .block-info {
            padding: 15px;
            background: var(--bg-gray);
            border-radius: 10px;
            border: 1px solid var(--border-color);
        }

        .block-info strong {
            color: var(--primary-blue);
            display: block;
            margin-bottom: 5px;
        }

        /* 任务列表排版 */
        .task-list {
            display: flex;
            flex-direction: column;
            gap: 40px;
        }

        .task-item {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 30px;
            align-items: start;
            padding-bottom: 30px;
            border-bottom: 1px dashed var(--border-color);
        }

        .task-item:last-child { border-bottom: none; }

        .task-media {
            background: #eee;
            border-radius: 12px;
            overflow: hidden;
            border: 1px solid var(--border-color);
            aspect-ratio: 4 / 3;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .task-media img {
            width: 100%;
            height: 100%;
            object-fit: cover;
        }

        .task-content {
            padding-top: 10px;
        }

        .task-num {
            display: inline-block;
            background: var(--primary-blue);
            color: #fff;
            padding: 2px 12px;
            border-radius: 20px;
            font-size: 12px;
            font-weight: 700;
            margin-bottom: 15px;
        }

        .task-title {
            font-size: 20px;
            font-weight: 700;
            margin-bottom: 15px;
        }

        .task-requirement {
            background: var(--soft-blue);
            padding: 20px;
            border-radius: 12px;
            border: 1px solid #d0e3ff;
        }

        .task-requirement h4 {
            font-size: 15px;
            margin-bottom: 8px;
            color: var(--primary-blue);
        }

        .task-requirement p {
            font-size: 17px;
            color: #000;
        }

        /* 提示信息 */
        .tip-box {
            background: #fff9db;
            border: 1px solid #ffe066;
            padding: 20px;
            border-radius: 12px;
            margin-top: 20px;
            display: flex;
            gap: 15px;
        }

        /* 页脚 */
        footer {
            background: #fff;
            border-top: 1px solid var(--border-color);
            padding: 40px 0;
            text-align: center;
        }

        .footer-content {
            max-width: var(--page-width);
            margin: 0 auto;
            color: var(--text-muted);
            font-size: 13px;
            line-height: 2;
        }

        .beian-links a {
            color: var(--text-muted);
            text-decoration: none;
            margin: 0 10px;
        }

        .beian-links a:hover { text-decoration: underline; }

        /* 响应式适配 */
        @media (max-width: 768px) {
            .task-item { grid-template-columns: 1fr; }
            .navbar-inner { padding: 0 15px; }
            .logo { font-size: 18px; }
            .nav-links { display: none; }
        }