h1 { margin:150px auto 30px auto; text-align:center;}
.image-container {
  max-width: 80%;
  min-width: 80%;
  min-height: 600px;
  margin-left: 12%;
  margin-bottom: 24px;
  border: 12px solid #fff;
  -webkit-box-shadow: 2px 2px 8px #000;
  box-shadow: 2px 2px 8px #000
}

img {
  max-width: 100%;
  max-height: 100%;
  -webkit-transition: opacity .5s;
  transition: opacity .5s
}

.visible-image { opacity: 1 }

.hidden-image { opacity: 0 }