.custom-gallery{
display: inline-block;
width: 100%;
}
.custom-gallery-item{
width:calc(25% – 10px);
display: inline-block;
float: left;
margin-right: 10px;
margin-bottom: 10px;
overflow: hidden;
height: 200px;
background-size: cover;
}
.custom-gallery-item img{opacity: 0;}
.custom-gallery-item:nth-child(4){margin-right: 0;}