:root {
            --primary-color: #1e40af;
            --secondary-color: #dc2626;
            --accent-color: #f59e0b;
            --text-color: #1f2937;
            --light-bg: #f8fafc;
        }
        body {
            font-family: 'Segoe UI', system-ui, sans-serif;
            line-height: 1.7;
            color: var(--text-color);
            background-color: var(--light-bg);
        }
        .navbar-brand {
            font-weight: 800;
            font-size: 1.8rem;
            color: var(--primary-color) !important;
            text-shadow: 2px 2px 4px rgba(0,0,0,0.1);
        }
        .hero-section {
            background: linear-gradient(135deg, var(--primary-color), #1e3a8a);
            color: white;
            padding: 4rem 0;
            margin-bottom: 3rem;
            border-radius: 0 0 20px 20px;
        }
        .content-section {
            background: white;
            border-radius: 15px;
            box-shadow: 0 5px 15px rgba(0,0,0,0.08);
            padding: 2.5rem;
            margin-bottom: 2rem;
        }
        h1, h2, h3 {
            color: var(--primary-color);
            margin-bottom: 1.5rem;
            font-weight: 700;
        }
        h1 {
            font-size: 2.5rem;
            border-bottom: 3px solid var(--accent-color);
            padding-bottom: 0.5rem;
        }
        h2 {
            font-size: 2rem;
            border-left: 5px solid var(--secondary-color);
            padding-left: 1rem;
            margin-top: 2.5rem;
        }
        h3 {
            font-size: 1.5rem;
            color: var(--secondary-color);
            margin-top: 2rem;
        }
        p {
            margin-bottom: 1.5rem;
            text-align: justify;
        }
        .key-term {
            font-weight: 700;
            color: var(--primary-color);
            background-color: #eff6ff;
            padding: 0.2rem 0.5rem;
            border-radius: 4px;
        }
        .game-feature {
            background: #f0f9ff;
            border-left: 4px solid var(--accent-color);
            padding: 1.5rem;
            margin: 1.5rem 0;
            border-radius: 0 8px 8px 0;
        }
        .img-container {
            text-align: center;
            margin: 2.5rem 0;
        }
        .img-container img {
            border-radius: 12px;
            box-shadow: 0 8px 16px rgba(0,0,0,0.1);
            max-width: 100%;
            height: auto;
        }
        .caption {
            font-style: italic;
            color: #6b7280;
            margin-top: 0.8rem;
            font-size: 0.9rem;
        }
        .nav-pills .nav-link.active {
            background-color: var(--primary-color);
            font-weight: 600;
        }
        .nav-pills .nav-link {
            color: var(--primary-color);
        }
        footer {
            background-color: var(--primary-color);
            color: white;
            padding: 2.5rem 0;
            margin-top: 4rem;
        }
        .content-highlight {
            background: linear-gradient(135deg, #fef3c7, #fde68a);
            padding: 2rem;
            border-radius: 12px;
            margin: 2rem 0;
            border: 2px dashed var(--accent-color);
        }
        @media (max-width: 768px) {
            .hero-section {
                padding: 2.5rem 0;
            }
            h1 {
                font-size: 2rem;
            }
            h2 {
                font-size: 1.7rem;
            }
            .content-section {
                padding: 1.5rem;
            }
        }
        .table-of-contents {
            background: #f8fafc;
            border-radius: 12px;
            padding: 2rem;
            margin-bottom: 2.5rem;
            border: 1px solid #e2e8f0;
        }
        .table-of-contents h3 {
            color: var(--primary-color);
            margin-top: 0;
            border-bottom: 2px solid var(--accent-color);
            padding-bottom: 0.5rem;
        }
        .table-of-contents ul {
            padding-left: 1.2rem;
        }
        .table-of-contents li {
            margin-bottom: 0.8rem;
        }
        .table-of-contents a {
            color: var(--primary-color);
            text-decoration: none;
            transition: color 0.3s;
        }
        .table-of-contents a:hover {
            color: var(--secondary-color);
            text-decoration: underline;
        }