img[src*="#gallery"] {
    width: 23%; /* thumbnail size */
    height: auto;
    border: 4px solid black;
    margin: 4px;
    transition: transform 0.3s ease, z-index 0.3s ease;
    cursor: zoom-in;
}
img[src*="#gallery"]:hover {
    transform: scale(4); /* zoom effect */
    z-index: 10;
    position: relative; /* so it overlays neighbors */
}