body {
    background-color: whitesmoke; /* whitesmoke */
}

/* When collapsed: show the 'plus' icon and hide the 'minus' icon */
.collapsed .bi-arrows-collapse { display: none; }
.collapsed .bi-arrows-expand { display: inline-block; }

/* When expanded (not collapsed): hide the 'plus' icon and show the 'minus' icon */
.btn:not(.collapsed) .bi-arrows-expand { display: none; }
.btn:not(.collapsed) .bi-arrows-collapse { display: inline-block; }