:root {
            --primary: #4a6fa5;
            --secondary: #ff6b6b;
            --accent: #51cf66;
            --dark: #2d3436;
            --light: #f8f9fa;
            --gray: #adb5bd;
            --shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
            --radius: 8px;
            --transition: all 0.3s ease;
            --max-width: 1200px;
        }
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        html {
            scroll-behavior: smooth;
        }
        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            line-height: 1.7;
            color: var(--dark);
            background-color: #fff;
            overflow-x: hidden;
        }
        .header-container {
            background: linear-gradient(135deg, var(--primary) 0%, #2c5282 100%);
            color: white;
            padding: 1rem 2rem;
            box-shadow: var(--shadow);
            position: sticky;
            top: 0;
            z-index: 1000;
        }
        .header-content {
            max-width: var(--max-width);
            margin: 0 auto;
            display: flex;
            justify-content: space-between;
            align-items: center;
        }
        .my-logo {
            font-size: 2.2rem;
            font-weight: 800;
            text-decoration: none;
            color: white;
            display: flex;
            align-items: center;
            gap: 0.5rem;
            font-family: 'Comic Sans MS', cursive, sans-serif;
            letter-spacing: 1px;
        }
        .my-logo i {
            color: var(--secondary);
        }
        .my-logo:hover {
            color: var(--accent);
            transform: scale(1.02);
            transition: var(--transition);
        }
        .desktop-nav {
            display: flex;
            gap: 2rem;
        }
        .desktop-nav a {
            color: white;
            text-decoration: none;
            font-weight: 600;
            padding: 0.5rem 1rem;
            border-radius: var(--radius);
            transition: var(--transition);
            position: relative;
        }
        .desktop-nav a:hover,
        .desktop-nav a.active {
            background-color: rgba(255, 255, 255, 0.15);
            color: var(--accent);
        }
        .desktop-nav a:hover::after {
            content: '';
            position: absolute;
            bottom: 0;
            left: 1rem;
            right: 1rem;
            height: 3px;
            background-color: var(--accent);
            border-radius: 3px;
        }
        .mobile-menu-toggle {
            display: none;
            background: none;
            border: none;
            color: white;
            font-size: 1.8rem;
            cursor: pointer;
            padding: 0.5rem;
        }
        .mobile-nav {
            display: none;
            flex-direction: column;
            background-color: var(--primary);
            position: absolute;
            top: 100%;
            left: 0;
            right: 0;
            padding: 1rem;
            box-shadow: var(--shadow);
            border-top: 2px solid rgba(255, 255, 255, 0.1);
        }
        .mobile-nav.active {
            display: flex;
        }
        .mobile-nav a {
            color: white;
            text-decoration: none;
            padding: 1rem;
            border-bottom: 1px solid rgba(255, 255, 255, 0.1);
            font-weight: 600;
            transition: var(--transition);
        }
        .mobile-nav a:hover {
            background-color: rgba(255, 255, 255, 0.1);
            padding-left: 1.5rem;
            color: var(--accent);
        }
        .breadcrumb {
            max-width: var(--max-width);
            margin: 1.5rem auto 0;
            padding: 0 2rem;
            font-size: 0.9rem;
            color: var(--gray);
        }
        .breadcrumb a {
            color: var(--primary);
            text-decoration: none;
        }
        .breadcrumb a:hover {
            text-decoration: underline;
            color: var(--secondary);
        }
        .breadcrumb span {
            margin: 0 0.5rem;
        }
        .main-container {
            max-width: var(--max-width);
            margin: 2rem auto;
            padding: 0 2rem;
            display: grid;
            grid-template-columns: 1fr 300px;
            gap: 3rem;
        }
        @media (max-width: 992px) {
            .main-container {
                grid-template-columns: 1fr;
                gap: 2rem;
            }
        }
        article {
            background: white;
            border-radius: var(--radius);
            padding: 2.5rem;
            box-shadow: var(--shadow);
        }
        h1 {
            font-size: 2.8rem;
            color: var(--primary);
            margin-bottom: 1.5rem;
            line-height: 1.2;
            border-bottom: 3px solid var(--accent);
            padding-bottom: 1rem;
        }
        h2 {
            font-size: 2rem;
            color: var(--dark);
            margin: 3rem 0 1.5rem;
            padding-bottom: 0.5rem;
            border-bottom: 2px solid var(--light);
        }
        h3 {
            font-size: 1.5rem;
            color: var(--primary);
            margin: 2.5rem 0 1rem;
        }
        h4 {
            font-size: 1.2rem;
            color: var(--secondary);
            margin: 2rem 0 0.8rem;
        }
        p {
            margin-bottom: 1.5rem;
            text-align: justify;
        }
        .intro {
            font-size: 1.2rem;
            color: var(--dark);
            background-color: #e7f5ff;
            padding: 1.5rem;
            border-left: 5px solid var(--primary);
            border-radius: var(--radius);
            margin-bottom: 2.5rem;
        }
        .highlight {
            background-color: #fff3bf;
            padding: 1.5rem;
            border-radius: var(--radius);
            margin: 2rem 0;
            border-left: 5px solid #ffd43b;
        }
        .category-grid {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
            gap: 1.5rem;
            margin: 2rem 0;
        }
        .category-card {
            background: white;
            border-radius: var(--radius);
            padding: 1.5rem;
            box-shadow: 0 2px 8px rgba(0,0,0,0.05);
            border: 1px solid #e9ecef;
            transition: var(--transition);
            display: flex;
            flex-direction: column;
        }
        .category-card:hover {
            transform: translateY(-5px);
            box-shadow: 0 8px 20px rgba(0,0,0,0.1);
            border-color: var(--accent);
        }
        .category-card h4 {
            color: var(--primary);
            margin-top: 0;
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }
        .category-card ul {
            padding-left: 1.2rem;
            margin-top: 1rem;
            flex-grow: 1;
        }
        .category-card li {
            margin-bottom: 0.5rem;
        }
        .difficulty-badge {
            display: inline-block;
            padding: 0.25rem 0.75rem;
            border-radius: 20px;
            font-size: 0.8rem;
            font-weight: 600;
            margin-left: 0.5rem;
        }
        .easy {
            background-color: #d3f9d8;
            color: #2b8a3e;
        }
        .medium {
            background-color: #ffec99;
            color: #e67700;
        }
        .hard {
            background-color: #ffc9c9;
            color: #c92a2a;
        }
        .featured-image {
            width: 100%;
            height: auto;
            border-radius: var(--radius);
            margin: 2rem 0;
            box-shadow: var(--shadow);
            border: 5px solid white;
        }
        blockquote {
            font-style: italic;
            color: var(--primary);
            border-left: 4px solid var(--secondary);
            padding-left: 1.5rem;
            margin: 2rem 0;
            background-color: #f8f9fa;
            padding: 1.5rem;
            border-radius: 0 var(--radius) var(--radius) 0;
        }
        .author {
            font-weight: bold;
            color: var(--dark);
            margin-top: 0.5rem;
            display: block;
        }
        .interactive-section {
            background: linear-gradient(to right, #f1f3f5, #e9ecef);
            padding: 2rem;
            border-radius: var(--radius);
            margin: 3rem 0;
        }
        .search-box, .comment-form, .rating-form {
            margin-bottom: 2rem;
        }
        .search-box h3, .comment-form h3, .rating-form h3 {
            margin-top: 0;
            color: var(--dark);
        }
        .form-group {
            margin-bottom: 1.5rem;
        }
        .form-group label {
            display: block;
            margin-bottom: 0.5rem;
            font-weight: 600;
            color: var(--dark);
        }
        input, textarea, select {
            width: 100%;
            padding: 0.8rem 1rem;
            border: 2px solid #dee2e6;
            border-radius: var(--radius);
            font-family: inherit;
            font-size: 1rem;
            transition: var(--transition);
        }
        input:focus, textarea:focus, select:focus {
            outline: none;
            border-color: var(--primary);
            box-shadow: 0 0 0 3px rgba(74, 111, 165, 0.2);
        }
        button {
            background-color: var(--primary);
            color: white;
            border: none;
            padding: 0.8rem 1.8rem;
            border-radius: var(--radius);
            font-weight: 600;
            cursor: pointer;
            transition: var(--transition);
            display: inline-flex;
            align-items: center;
            gap: 0.5rem;
        }
        button:hover {
            background-color: #3a5a8c;
            transform: translateY(-2px);
            box-shadow: 0 4px 8px rgba(0,0,0,0.1);
        }
        button.secondary {
            background-color: var(--secondary);
        }
        button.secondary:hover {
            background-color: #ff5252;
        }
        .stars {
            display: flex;
            gap: 0.5rem;
            margin: 1rem 0;
        }
        .star {
            font-size: 1.8rem;
            color: var(--gray);
            cursor: pointer;
            transition: var(--transition);
        }
        .star:hover,
        .star.active {
            color: #ffd43b;
        }
        .update-time {
            font-size: 0.9rem;
            color: var(--gray);
            text-align: right;
            margin-top: 3rem;
            padding-top: 1rem;
            border-top: 1px solid #dee2e6;
        }
        .update-time i {
            margin-right: 0.5rem;
            color: var(--accent);
        }
        .sidebar {
            background: white;
            border-radius: var(--radius);
            padding: 2rem;
            box-shadow: var(--shadow);
            align-self: start;
            position: sticky;
            top: 120px;
        }
        .sidebar h3 {
            color: var(--primary);
            margin-top: 0;
            padding-bottom: 0.5rem;
            border-bottom: 2px solid var(--light);
        }
        .toc {
            list-style: none;
            margin: 1.5rem 0;
        }
        .toc li {
            margin-bottom: 0.8rem;
        }
        .toc a {
            color: var(--dark);
            text-decoration: none;
            display: block;
            padding: 0.5rem 0;
            border-left: 3px solid transparent;
            transition: var(--transition);
            padding-left: 0.5rem;
        }
        .toc a:hover,
        .toc a.active {
            color: var(--primary);
            border-left-color: var(--secondary);
            padding-left: 1rem;
            background-color: #f8f9fa;
        }
        .related-links {
            margin-top: 2rem;
        }
        .related-links a {
            display: block;
            color: var(--primary);
            text-decoration: none;
            padding: 0.8rem;
            margin-bottom: 0.5rem;
            border-radius: var(--radius);
            background-color: #f1f3f5;
            transition: var(--transition);
        }
        .related-links a:hover {
            background-color: #e7f5ff;
            color: var(--secondary);
            transform: translateX(5px);
        }
        .related-links a i {
            margin-right: 0.5rem;
            color: var(--accent);
        }
        footer {
            background-color: var(--dark);
            color: white;
            padding: 3rem 2rem 2rem;
            margin-top: 4rem;
        }
        .footer-content {
            max-width: var(--max-width);
            margin: 0 auto;
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
            gap: 3rem;
        }
        .footer-section h4 {
            color: white;
            margin-bottom: 1.5rem;
            font-size: 1.2rem;
        }
        .footer-section a {
            color: #adb5bd;
            text-decoration: none;
            display: block;
            margin-bottom: 0.8rem;
            transition: var(--transition);
        }
        .footer-section a:hover {
            color: var(--accent);
            padding-left: 0.5rem;
        }
        friend-link {
            display: block;
            background-color: rgba(255, 255, 255, 0.05);
            padding: 1rem;
            border-radius: var(--radius);
            margin-bottom: 1rem;
            border-left: 3px solid var(--accent);
        }
        friend-link a {
            color: white !important;
            font-weight: 600;
        }
        friend-link a:hover {
            color: var(--accent) !important;
        }
        .copyright {
            text-align: center;
            margin-top: 3rem;
            padding-top: 2rem;
            border-top: 1px solid rgba(255, 255, 255, 0.1);
            color: #adb5bd;
            font-size: 0.9rem;
        }
        @media (max-width: 768px) {
            .header-content {
                flex-wrap: wrap;
            }
            .desktop-nav {
                display: none;
            }
            .mobile-menu-toggle {
                display: block;
            }
            h1 {
                font-size: 2.2rem;
            }
            h2 {
                font-size: 1.7rem;
            }
            h3 {
                font-size: 1.3rem;
            }
            article {
                padding: 1.5rem;
            }
            .main-container {
                padding: 0 1rem;
            }
            .breadcrumb {
                padding: 0 1rem;
            }
            .category-grid {
                grid-template-columns: 1fr;
            }
            .sidebar {
                position: static;
                top: auto;
            }
        }
        .emoji {
            font-size: 1.2em;
            margin-right: 0.3rem;
        }
        .bold {
            font-weight: 800;
            color: var(--primary);
        }
        .italic {
            font-style: italic;
            color: #495057;
        }
        .text-center {
            text-align: center;
        }
        .mb-3 {
            margin-bottom: 3rem;
        }
        .mt-3 {
            margin-top: 3rem;
        }
        .py-2 {
            padding-top: 2rem;
            padding-bottom: 2rem;
        }
        .link {
            color: var(--primary);
            text-decoration: none;
            border-bottom: 1px dotted var(--primary);
            transition: var(--transition);
        }
        .link:hover {
            color: var(--secondary);
            border-bottom-style: solid;
        }