/* page layout */

body,
html {
  width: 100%;
  height: 90%;
  font-family: Arial, sans-serif;
  overflow: hidden;
  margin: 0;
  font-size: 20px;
  background: #1d1d1d;
  display: flex;
  align-items: center;
  justify-content: center;
}
* {
  position: relative;
  box-sizing: border-box;
}
.gallery {
  visibility: hidden;
  width: 640px;
  height: 480px;
  overflow: hidden;
}

.gallery img {
  width: 640px;
  height: 480px;
  position: absolute;
}