Code

//* Grid Gallery Captions on Hover *//
.gallery-grid .gallery-caption {
 position: absolute;
 top: 0;
 left: 0;
 background: rgba(0,0,0,0.6); // overlay color 
 height: 100%;
 padding: 0;
 opacity: 0;
 pointer-events: none;
}
.gallery-grid .gallery-caption-wrapper {
 display: flex;
 align-items: center; // center caption box vertically 
 justify-content: center; // center caption box horizontally
}
.gallery-grid .gallery-caption-content {
 font-size: 1rem !important; // caption font size
 color: white; //caption font color 
 padding: 1vw; // padding around the caption
 text-align: center; // center text within caption box
}
.gallery-grid-item {
 position: relative;
}
.gallery-grid-item:hover .gallery-caption {
 opacity: 1;
}
.gallery-caption-grid-simple {
 transition-delay: 0ms;
 max-width: unset;
}