html,
body {
  height: 100%;
  margin: 0;
  background: #333;
}

ul {
  margin: 0;
  padding: 1px;
}

.app {
  height: 100%;
}

.app ul {
  display: flex;
  flex-wrap: wrap;
}

.app li {
  box-sizing: border-box;
  flex: 1;
  min-width: 80px;
  max-width: 25%;
  padding: 2px;
  /* height: 100px; */
  list-style: none;
}

.app li > img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  opacity: 0;
  box-shadow: 0 2px 10px rgba(0,0,0,0.5);
  transform: scale(3);
  transition: all 400ms;
}

.app li > img.loaded {
  transform: scale(1);
  opacity: 1;
}