WordPress 6.4 added an “Expand on click” feature to image blocks.. ..here is how i added styles for it to my themes..
/* image wp-lightbox-overlay styles */
.wp-lightbox-overlay .scrim {
background-color: rgba(0,0,0,0.9) !important;
}
.wp-lightbox-overlay .close-button {
border: 1px solid #fff !important;
background-color: #fff !important;
border-radius: 50%;
box-shadow: 0 2px 4px rgba(0,0,0,0.2);
}
.wp-lightbox-overlay .close-button:hover,
.wp-lightbox-overlay .close-button:focus {
border: 1px solid #ddd !important;
background-color: #ddd !important;
outline: none;
}