body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

header {
    background-color: #13829e;
    padding: 2em;
    text-align: center;
}

.logo {
    color: white;
    text-decoration: none;
    font-size: 2em;
    font-weight: bold;
}

.navigation {
    margin-top: 10px;
}

.navigation a {
    color: white;
    margin: 0 10px;
    text-decoration: none;
    font-weight: bold;
}

.main_text {
    padding: 20px;
    text-align: center;
}

@media (max-width: 768px) {
    .navigation {
        flex-direction: column;
    }

    .navigation a {
        margin: 10px 0;
    }
}