overlay css
#overlay {
position: fixed; /* Sit on top of the page content */
display: none; /* Hidden by default */
width: 100%; /* Full width (cover the whole page) */
height: 100%; /* Full height (cover the whole page) */
top: 0;
left: 0;
right: 0;
bottom: 0;
background-color: rgba(0,0,0,0.5); /* Black background with opacity */
z-index: 2; /* Specify a stack order in case you're using a different order for other elements */
cursor: pointer; /* Add a pointer on hover */
}