Opacity

:root {
  align-items: center;
}

.items {
  flex-direction: row;
  align-items: center;
}

.item1, .item2, .item3 {
  width: 100px;
  height: 100px;
  transition: opacity 200ms;
  cursor: pointer;
  margin: 20px;
}

.item1:hover {
  opacity: 0.4;
}

.item2:hover {
  opacity: 80%;
}

.item3:hover {
  opacity: 5%;
}