style.css

body {
  height:100%;
  width:100%;
  margin:0;
  padding:0;
}

.header {
  margin-top:1rem;
  height:100px;
}

.photos .img {
  width:100vw;
  height:40vh;
  display:block;
  background-size: cover;
  background-position:center;
  position:relative;
  text-align: center;
  cursor: pointer;
  transition: all .4s ease;
}

.photos .img:hover {
  box-shadow: inset 0px 0px 50vw 20px rgba(0,0,0,0.5);
}

.photos .img:hover span {
  opacity:1;
}

.photos .img span {
  opacity: 0;
  position:absolute;
  left:0;
  right:0;
  bottom:10px;
  margin:0 auto;
  transition: all .8s ease;
}

.photos .img span,
.photos .img span a {
  font-size:12px;
  color:#fff;
  text-shadow:0px 0px 2px #000;
}

.photos .img span a {
  text-decoration: none;
}

.photos .img span a:hover {
  text-decoration: underline
}

@media(min-width:768px) {
  .header{
    height:54px;
  }
  .photos .img {
    width:calc(50vw - 8.5px); /* windows scroll bars */
    height:calc(50vh - 27px);
    float:left;
  }
}