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

        body {
            font-family: 'Georgia', 'Times New Roman', serif;
            line-height: 1.8;
            color: #2c3e50;
            background-color: #f8f9fa;
            padding: 20px;
            max-width: 900px;
            margin: 0 auto;
        }

        .container {
            background-color: #ffffff;
            padding: 40px;
            border-radius: 10px;
            box-shadow: 0 2px 10px rgba(0,0,0,0.1);
            margin-bottom: 100px;
        }

        h1 {
            color: #1a252f;
            font-size: 2em;
            margin-bottom: 20px;
            text-align: center;
            border-bottom: 3px solid #3498db;
            padding-bottom: 15px;
        }

        h2 {
            color: #2c3e50;
            font-size: 1.5em;
            margin-top: 40px;
            margin-bottom: 20px;
            border-left: 4px solid #3498db;
            padding-left: 15px;
        }

        h3 {
            color: #34495e;
            font-size: 1.4em;
            margin-top: 30px;
            margin-bottom: 15px;
        }

        h4 {
            color: #34495e;
            font-size: 1.2em;
            margin-top: 25px;
            margin-bottom: 10px;
            font-weight: bold;
        }

        p {
            margin-bottom: 15px;
            text-align: justify;
        }

        .author-info {
            text-align: center;
            margin-bottom: 30px;
            color: #7f8c8d;
            font-style: italic;
        }

        .floating-buttons {
            position: fixed;
            bottom: 30px;
            right: 30px;
            display: flex;
            flex-direction: column;
            gap: 15px;
            z-index: 1000;
        }

        .floating-btn {
            width: 60px;
            height: 60px;
            border-radius: 25%;
            border: none;
            background-color: #3498db;
            color: white;
            font-size: 20px;
            cursor: pointer;
            box-shadow: 0 4px 15px rgba(52, 152, 219, 0.3);
            transition: all 0.3s ease;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .floating-btn:hover {
            background-color: #2980b9;
            transform: translateY(-3px);
            box-shadow: 0 6px 20px rgba(52, 152, 219, 0.4);
        }

        .modal {
            display: none;
            position: fixed;
            z-index: 2000;
            left: 0;
            top: 0;
            width: 100%;
            height: 100%;
            background-color: rgba(0,0,0,0.5);
        }

        .modal-content {
            background-color: #fefefe;
            margin: 5% auto;
            padding: 30px;
            border-radius: 10px;
            width: 80%;
            max-width: 600px;
            max-height: 80vh;
            overflow-y: auto;
            position: relative;
        }

        .close {
            color: #aaa;
            float: right;
            font-size: 28px;
            font-weight: bold;
            cursor: pointer;
            position: absolute;
            top: 15px;
            right: 25px;
        }

        .close:hover {
            color: #000;
        }

        .toc-item, .ref-item {
            padding: 10px 0;
            border-bottom: 1px solid #ecf0f1;
            cursor: pointer;
            transition: background-color 0.3s ease;
        }

        .toc-item:hover, .ref-item:hover {
            background-color: #ecf0f1;
            padding-left: 10px;
        }

        .toc-item.level-1 {
            font-weight: bold;
            font-size: 1.1em;
        }

        .toc-item.level-2 {
            padding-left: 20px;
            font-size: 1em;
        }

        .toc-item.level-3 {
            padding-left: 40px;
            font-size: 0.9em;
            color: #7f8c8d;
        }

        .ref-item a {
            color: #3498db;
            text-decoration: none;
        }

        .ref-item a:hover {
            text-decoration: underline;
        }

        /* Smooth scrolling */
        html {
            scroll-behavior: smooth;
        }

        /* Responsive design */
        @media (max-width: 768px) {
            body {
                padding: 10px;
            }
            
            .container {
                padding: 20px;
            }
            
            h1 {
                font-size: 2em;
            }
            
            .floating-buttons {
                bottom: 20px;
                right: 20px;
            }
            
            .floating-btn {
                width: 50px;
                height: 50px;
                font-size: 16px;
            }
            
            .modal-content {
                width: 95%;
                margin: 10% auto;
                padding: 20px;
            }
        }