h1 {
   text-align: center;
   margin: 35px 0;
}
.gallery {
   max-width: 1000px;
   margin: 0 auto;
}
figure img {
   width: 250px;
   height: 250px;
   object-fit: cover;
   padding: 5px;
   background-color: white;
   box-shadow: 5px 5px 15px black;
   display: block;
   margin: 0 auto;
}

/* modal */
dialog img {
   width: 90%;
   display: block;
   margin: 20vh auto;
}
dialog {
   width: 100%;
   height: 100%;
   background-color: rgba(0,0,0,.75);
}
.close-viewer {
   position: absolute;
   top: 10vh;
   right: 2vh;
   padding: 3px 6px;
   font-size: 1.5em;
}

@media screen and (min-width: 700px) {
   .gallery {
       display: grid;
       grid-template-columns: 1fr 1fr;
   }
}
@media screen and (min-width: 1000px) {
   .gallery {
       grid-template-columns: 1fr 1fr 1fr;
   }
   dialog img {
       width: 60%;
       margin: 15vh auto;
   }
   .close-viewer {
       position: absolute;
       right: 15vh;
   }
   .viewer {
       margin: 50px;
       padding: 50px;
   }
   .viewer img {
       max-width: 800px;
   }
}