body {
    font-family: 'Roboto', sans-serif;
    background-color: <?php echo $backgroundColor; ?>;
    margin: 0;
}
header {
background-image: url('https://picsum.photos/1200/400');
    background-size: cover;
    background-position: center;
    background-color: #34495e;
    color: white;
    padding: 30px;
    position: relative;
}
header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 0;
    height: 0;
    border-left: 100px solid #2ecc71;
    border-bottom: 100px solid transparent;
}
header::after {
    content: '';
    position: absolute;
    top: 0;
    right: 0;
    width: 0;
    height: 0;
    border-right: 100px solid #3498db;
    border-top: 100px solid transparent;
}
nav {
    background-color: #2c3e50;
    text-align: center;
    padding: 10px;
}
nav a {
    color: white;
    padding: 10px 20px;
    text-decoration: none;
}
nav a:hover {
    background-color: #2980b9;
}