.boven {
    display: block;
    width: 100%; /* Optional: set width as needed */
    height: 75vh; /* 80% of the viewport height */
    border: none; /* Remove default border */
}
.onder {
    display: block;
    width: 100%; /* Optional: set width as needed */
    height: 20vh; /* 80% of the viewport height */
    border: none; /* Remove default border */
}