Overlays
Problem: adding an overlay to an image.
Solution: use `::after` psendo-element.
.image-overlay {
position: relative;
}
.image-overlay::after {
content: '';
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
background-color: rgba(0, 0, 0, 0.5); /* black with 50% opacity */
}