adding overlay on body if there is a div in Dom code example
Example 1: div color overlay css
box-shadow: inset 0 0 0 2000px rgb(0 0 0 / 67%);
Example 2: overlay a box in css
html, body {
min-height: 100%;
}
body {
position: relative; /* needed if you position the pseudo-element absolutely */
}
body:after {
content: "";
display: block;
position: fixed; /* could also be absolute */
top: 0;
left: 0;
height: 100%;
width: 100%;
z-index: 10;
background-color: rgba(0,0,0,0.2);
}