.lightbox {
/* default to hidden */
display: none;

/*overlay entire screen */
position: fixed;
z-index: 999;
top: 0;
left: 0;
right: 0;
bottom: 0;

/*A bit of padding around image */
padding: 1em;

/*Translucent background */
background: rgba(0,0,0,0.8);
}
/* Unhide lightbox when targeted */
.lightbox:target {
display: block;
}

.lightbox span {
/* Full width and height */
display: block;
width: 100%;
height: 100%;

/* Size and position background image */
background-position: center;
background-repeat: no-repeat;
background-size: contain;
}