body {
    font-family: 'Open Sans', sans-serif;
    margin: 0;
    padding: 0;
    background-color: #fff;
    color: #333;
}

header {
    background: #003865;
    color: #fff;
    padding: 0;
    text-align: center;
}

header .topnav {
    display: flex;
    justify-content: center;
    background: #003865;
    padding: 0.5rem 0;
    flex-wrap: wrap; /* Allow wrapping on smaller screens */
    border-bottom: 4px solid #ffc107; /* Add yellow underline */
}

header .topnav button {
    background: none;
    border: none;
    color: #fff;
    padding: 1rem 2rem;
    cursor: pointer;
    font-size: 1rem;
    transition: background 0.3s ease;
    position: relative; /* For the pseudo-element */
}

header .topnav button:hover {
    background: #002950;
}

header .topnav button:after {
    content: '';
    display: block;
    width: 100%;
    height: 4px; /* Height of the yellow line */
    background: #ffc107; /* Yellow color */
    position: absolute;
    bottom: 0;
    left: 0;
    transition: transform 0.3s ease;
    transform: scaleX(0);
}

header .topnav button:hover:after {
    transform: scaleX(1);
}

.main-container {
    display: flex;
    margin: 1rem auto;
    max-width: 1200px;
    padding: 0 2rem;
}

.sidebar {
    flex: 0 0 200px;
    text-align: center;
    padding: 1rem;
}

.sidebar img {
    width: 100%;
    height: auto;
    border-radius: 5px;
}

.sidebar p {
    font-weight: bold;
    color: #003865;
    margin-top: 1rem;
}

main {
    flex: 1;
    padding: 1rem 2rem;
}

section {
    display: none;
    padding: 2rem 0;
}

section h2 {
    color: #003865;
    border-bottom: 2px solid #003865;
    padding-bottom: 0.5rem;
    margin-bottom: 1rem;
}

.publication-year h3 {
    color: orange;
    margin-bottom: 0.5rem;
}

footer {
    text-align: center;
    padding: 1rem 0;
    background: #003865;
    color: #fff;
}

a {
    color: #003865;
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

/* Responsive styles */
@media (max-width: 768px) {
    .main-container {
        flex-direction: column;
        padding: 0;
    }

    .sidebar {
        flex: 0 0 auto;
        padding: 1rem 0;
        text-align: center;
    }

    .sidebar img {
        width: 50%;
        margin: 0 auto;
    }

    .sidebar p {
        font-size: 1rem;
    }

    main {
        padding: 1rem;
    }

    header .topnav button {
        padding: 0.5rem 1rem;
        font-size: 0.9rem;
    }
}

@media (max-width: 480px) {
    header .topnav {
        flex-direction: column;
    }

    header .topnav button {
        padding: 0.5rem;
        font-size: 0.8rem;
    }

    .sidebar img {
        width: 75%;
        margin: 0 auto;
    }

    main {
        padding: 1rem;
    }
}