body {
  background: #222;
  -webkit-overflow-scrolling: touch;
}

.container {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
}

[data-scroll] {
  background-color: lightgray;
  background-size: cover;
  background-repeat: no-repeat;
  border-radius: 5px;
  width: calc(33.333% - 20px);
  height: 250px;
  margin: 10px;
  will-change: transform;
  opacity: 1;
  opacity: calc(var(--visible-y) * var(--visible-y));
  transform: scale(calc(0.5 + calc(var(--visible-y) * 0.5)));
}