* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
        }
        :root {
            --primary-color: #4a6fa5;
            --secondary-color: #ff9a3d;
            --accent-color: #16697a;
            --text-dark: #333;
            --text-light: #666;
            --background-light: #f8f9fa;
            --background-white: #ffffff;
            --shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
            --border-radius: 12px;
            --transition: all 0.3s ease;
        }
        html {
            scroll-behavior: smooth;
        }
        body {
            background-color: var(--background-light);
            color: var(--text-dark);
            line-height: 1.6;
            display: flex;
            flex-direction: column;
            min-height: 100vh;
        }
        a {
            text-decoration: none;
            color: inherit;
            transition: var(--transition);
        }
        ul {
            list-style: none;
        }
        img {
            max-width: 100%;
            height: auto;
            display: block;
        }
        .container {
            width: 100%;
            max-width: 1200px;
            margin: 0 auto;
            padding: 0 20px;
        }
        header {
            background-color: var(--background-white);
            box-shadow: var(--shadow);
            position: sticky;
            top: 0;
            z-index: 1000;
        }
        .header-top {
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 15px 0;
        }
        .logo {
            font-size: 2rem;
            font-weight: 800;
            color: var(--primary-color);
            display: flex;
            align-items: center;
            gap: 10px;
        }
        .logo i {
            color: var(--secondary-color);
        }
        .logo span {
            background: linear-gradient(45deg, var(--primary-color), var(--accent-color));
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
        }
        .search-form {
            display: flex;
            max-width: 400px;
            width: 100%;
        }
        .search-input {
            flex: 1;
            padding: 12px 18px;
            border: 2px solid #ddd;
            border-radius: 30px 0 0 30px;
            font-size: 1rem;
            outline: none;
            transition: var(--transition);
        }
        .search-input:focus {
            border-color: var(--primary-color);
        }
        .search-btn {
            background-color: var(--primary-color);
            color: white;
            border: none;
            border-radius: 0 30px 30px 0;
            padding: 12px 25px;
            cursor: pointer;
            font-size: 1rem;
            transition: var(--transition);
        }
        .search-btn:hover {
            background-color: var(--accent-color);
        }
        nav {
            border-top: 1px solid #eee;
            padding: 10px 0;
        }
        .nav-list {
            display: flex;
            justify-content: center;
            gap: 30px;
            flex-wrap: wrap;
        }
        .nav-item a {
            font-weight: 600;
            padding: 8px 15px;
            border-radius: var(--border-radius);
            color: var(--text-light);
        }
        .nav-item a:hover,
        .nav-item a.active {
            color: var(--primary-color);
            background-color: rgba(74, 111, 165, 0.1);
        }
        .hamburger {
            display: none;
            font-size: 1.8rem;
            cursor: pointer;
            color: var(--primary-color);
        }
        .breadcrumb {
            padding: 15px 0;
            background-color: #f0f4f8;
            font-size: 0.9rem;
            margin-bottom: 20px;
        }
        .breadcrumb-list {
            display: flex;
            flex-wrap: wrap;
            gap: 10px;
        }
        .breadcrumb-item:not(:last-child)::after {
            content: '›';
            margin-left: 10px;
            color: var(--text-light);
        }
        .breadcrumb-item a:hover {
            color: var(--primary-color);
            text-decoration: underline;
        }
        main {
            flex: 1;
            padding: 20px 0 40px;
        }
        .article-container {
            display: grid;
            grid-template-columns: 1fr 300px;
            gap: 30px;
        }
        @media (max-width: 992px) {
            .article-container {
                grid-template-columns: 1fr;
            }
        }
        .article-content {
            background-color: var(--background-white);
            border-radius: var(--border-radius);
            padding: 30px;
            box-shadow: var(--shadow);
        }
        .article-header {
            margin-bottom: 30px;
            border-bottom: 2px solid #eee;
            padding-bottom: 20px;
        }
        .article-title {
            font-size: 2.2rem;
            color: var(--text-dark);
            margin-bottom: 15px;
            line-height: 1.3;
        }
        .article-meta {
            display: flex;
            gap: 20px;
            color: var(--text-light);
            font-size: 0.9rem;
        }
        .article-meta span {
            display: flex;
            align-items: center;
            gap: 5px;
        }
        .content-section {
            margin-bottom: 40px;
        }
        h2 {
            font-size: 1.8rem;
            color: var(--primary-color);
            margin-bottom: 20px;
            padding-bottom: 10px;
            border-bottom: 2px dashed #eee;
        }
        h3 {
            font-size: 1.4rem;
            color: var(--accent-color);
            margin: 25px 0 15px;
        }
        p {
            margin-bottom: 20px;
            text-align: justify;
            font-size: 1.05rem;
        }
        .highlight {
            background-color: #fff9e6;
            border-left: 4px solid var(--secondary-color);
            padding: 20px;
            margin: 25px 0;
            border-radius: 0 var(--border-radius) var(--border-radius) 0;
        }
        .tip-box {
            background-color: #e8f4f8;
            border: 1px solid #b8e2f0;
            border-radius: var(--border-radius);
            padding: 20px;
            margin: 25px 0;
            display: flex;
            gap: 15px;
        }
        .tip-icon {
            color: var(--accent-color);
            font-size: 1.5rem;
            flex-shrink: 0;
        }
        .solution-box {
            background-color: #f0f7f0;
            border: 1px solid #c5e1c5;
            border-radius: var(--border-radius);
            padding: 25px;
            margin: 30px 0;
            text-align: center;
        }
        .solution-title {
            color: #2e7d32;
            font-size: 1.5rem;
            margin-bottom: 15px;
        }
        .equation {
            font-size: 2.5rem;
            font-weight: bold;
            color: var(--primary-color);
            margin: 20px 0;
            font-family: 'Courier New', monospace;
        }
        .article-image {
            margin: 30px 0;
            text-align: center;
        }
        .article-image img {
            border-radius: var(--border-radius);
            box-shadow: var(--shadow);
            max-width: 800px;
            width: 100%;
            margin: 0 auto;
        }
        .image-caption {
            font-style: italic;
            color: var(--text-light);
            margin-top: 10px;
            font-size: 0.95rem;
        }
        .sidebar {
            display: flex;
            flex-direction: column;
            gap: 25px;
        }
        .sidebar-widget {
            background-color: var(--background-white);
            border-radius: var(--border-radius);
            padding: 25px;
            box-shadow: var(--shadow);
        }
        .widget-title {
            font-size: 1.3rem;
            color: var(--primary-color);
            margin-bottom: 20px;
            padding-bottom: 10px;
            border-bottom: 2px solid #eee;
            display: flex;
            align-items: center;
            gap: 10px;
        }
        .widget-title i {
            color: var(--secondary-color);
        }
        .related-links {
            display: flex;
            flex-direction: column;
            gap: 12px;
        }
        .related-link {
            padding: 12px 15px;
            background-color: #f8f9fa;
            border-radius: 8px;
            transition: var(--transition);
            display: flex;
            align-items: center;
            gap: 10px;
        }
        .related-link:hover {
            background-color: #e9ecef;
            transform: translateX(5px);
        }
        .related-link i {
            color: var(--primary-color);
        }
        .rating-section,
        .comment-section {
            background-color: var(--background-white);
            border-radius: var(--border-radius);
            padding: 30px;
            box-shadow: var(--shadow);
            margin-top: 30px;
        }
        .rating-form,
        .comment-form {
            display: flex;
            flex-direction: column;
            gap: 20px;
            margin-top: 20px;
        }
        .stars {
            display: flex;
            gap: 5px;
            direction: ltr;
        }
        .star {
            font-size: 2rem;
            color: #ddd;
            cursor: pointer;
            transition: var(--transition);
        }
        .star:hover,
        .star.active {
            color: #ffc107;
        }
        .form-group {
            display: flex;
            flex-direction: column;
            gap: 8px;
        }
        .form-label {
            font-weight: 600;
        }
        .form-input,
        .form-textarea {
            padding: 14px;
            border: 1px solid #ddd;
            border-radius: var(--border-radius);
            font-size: 1rem;
            transition: var(--transition);
        }
        .form-input:focus,
        .form-textarea:focus {
            border-color: var(--primary-color);
            outline: none;
        }
        .form-textarea {
            min-height: 150px;
            resize: vertical;
        }
        .submit-btn {
            background-color: var(--primary-color);
            color: white;
            border: none;
            border-radius: var(--border-radius);
            padding: 15px 30px;
            font-size: 1.1rem;
            font-weight: 600;
            cursor: pointer;
            transition: var(--transition);
            align-self: flex-start;
        }
        .submit-btn:hover {
            background-color: var(--accent-color);
        }
        .comments-list {
            margin-top: 30px;
            display: flex;
            flex-direction: column;
            gap: 25px;
        }
        .comment-item {
            background-color: #f8f9fa;
            border-radius: var(--border-radius);
            padding: 20px;
            border-left: 4px solid var(--primary-color);
        }
        .comment-header {
            display: flex;
            justify-content: space-between;
            margin-bottom: 15px;
            flex-wrap: wrap;
            gap: 10px;
        }
        .comment-author {
            font-weight: 600;
            color: var(--primary-color);
        }
        .comment-date {
            color: var(--text-light);
            font-size: 0.9rem;
        }
        .comment-rating {
            color: #ffc107;
        }
        .footer-links {
            background-color: #2c3e50;
            color: white;
            padding: 40px 0 20px;
            margin-top: 50px;
        }
        .web-links-container {
            display: grid;
            grid-template-columns: repeat(5, 1fr);
            gap: 20px;
            margin-bottom: 30px;
        }
        @media (max-width: 768px) {
            .web-links-container {
                grid-template-columns: repeat(2, 1fr);
            }
        }
        .web-link {
            background-color: rgba(255, 255, 255, 0.1);
            padding: 15px;
            border-radius: 8px;
            text-align: center;
            transition: var(--transition);
        }
        .web-link:hover {
            background-color: rgba(255, 255, 255, 0.2);
            transform: translateY(-5px);
        }
        footer {
            background-color: #1a252f;
            color: #bdc3c7;
            text-align: center;
            padding: 25px 0;
        }
        .copyright {
            font-size: 0.9rem;
            line-height: 1.6;
        }
        .copyright a {
            color: var(--secondary-color);
        }
        .copyright a:hover {
            text-decoration: underline;
        }
        @media (max-width: 768px) {
            .header-top {
                flex-direction: column;
                gap: 20px;
            }
            .search-form {
                max-width: 100%;
            }
            .nav-list {
                flex-direction: column;
                display: none;
                width: 100%;
                background-color: white;
                padding: 20px;
                border-radius: var(--border-radius);
                box-shadow: var(--shadow);
                margin-top: 15px;
            }
            .nav-list.active {
                display: flex;
            }
            .hamburger {
                display: block;
                position: absolute;
                top: 20px;
                right: 20px;
            }
            .article-title {
                font-size: 1.8rem;
            }
            .article-meta {
                flex-direction: column;
                gap: 10px;
            }
            h2 {
                font-size: 1.5rem;
            }
            h3 {
                font-size: 1.2rem;
            }
            .equation {
                font-size: 1.8rem;
            }
        }