anchor.diff:    margin: 0 auto;
     overflow: auto;
     padding: 10px 0;
  +  display:         flex;
  +  flex-wrap:       wrap;
  +  justify-content: center;
   }
   
   .tile {
  
positive.code:   height: 130px;
  }
  
  @media only screen and (max-width: 800px) {
   .tile {
     width: 30%;
   }
  
negative.code: 
  @media only screen and (max-width: 400px) {
    .tile {
     max-width: 100%;
   }
  } %>
  
  .citation {
    color: #4C4C4C;
  