:root {
            --primary-color: #006699;
            --text-color: #333;
            --spacing: 1rem;
        }

        body {
            font-family: Verdana, Arial, Helvetica, sans-serif;
            font-size: 14px;
            line-height: 1.6;
            color: var(--text-color);
            margin: 0;
            padding: var(--spacing);
            text-align: center;
        }

        header {
            margin-bottom: 2rem;
        }

        h1 {
            font-size: 1.8rem;
            margin-bottom: 0.5rem;
            text-align: center;
        }

        h2 {
            font-size: 1.5rem;
            color: var(--primary-color);
            margin-top: 2rem;
            text-align: center;
        }

        h3 {
            text-align: center;
        }

        h4 {
            font-size: 1.1rem;
            margin-bottom: 1rem;
            text-align: center;
        }

        nav {
            background: #f5f5f5;
            padding: 1rem;
            margin-bottom: 2rem;
        }

        nav ul {
            list-style: none;
            padding: 0;
            display: flex;
            flex-wrap: wrap;
            gap: 1rem;
            justify-content: center;
        }

        nav a {
            color: var(--primary-color);
            text-decoration: none;
        }

        nav a:hover {
            text-decoration: underline;
        }

        main {
            max-width: 800px;
            margin: 0 auto;
            text-align: center;
        }

        article {
            border: 1px solid var(--primary-color);
            padding: 1.5rem;
            margin-bottom: 2rem;
            text-align: left;
        }

        article h3 {
            font-size: 1.2rem;
            margin-top: 0;
            color: var(--primary-color);
            text-align: center;
        }

        article p {
            margin-bottom: 1rem;
            text-align: justify;
        }

        sup {
            font-size: 0.75em;
            color: var(--primary-color);
        }

        .footnotes {
            font-size: 0.85rem;
            margin-top: 2rem;
            padding-top: 1rem;
            border-top: 1px solid #ccc;
            text-align: left;
        }

        .footnotes h3 {
            text-align: left;
        }

        .footnotes p {
            margin-bottom: 0.5rem;
            text-align: left;
        }

        .alphabet-nav {
            margin: 2rem 0;
            text-align: center;
        }

        .alphabet-nav a {
            display: inline-block;
            padding: 0.3rem 0.6rem;
            margin: 0.2rem;
            color: var(--primary-color);
            text-decoration: none;
            border: 1px solid #ddd;
            border-radius: 3px;
        }

        .alphabet-nav a:hover {
            background: var(--primary-color);
            color: white;
        }

        footer {
            margin-top: 3rem;
            padding-top: 1rem;
            border-top: 1px solid #ccc;
            font-size: 0.9rem;
            text-align: center;
        }

        footer nav {
            background: transparent;
            padding: 0;
        }

        footer nav ul {
            justify-content: center;
        }

        @media (max-width: 768px) {
            nav ul {
                flex-direction: column;
            }
            
            article {
                padding: 1rem;
            }
        }