* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

.box, div[data-active-target] {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 100%;
  height: 500px;
  color: #ffffff;
  font-size: 100px;
  margin-bottom: 50px;
  opacity: 0;
  transition: opacity 1s ease-in-out;
}

.box, div[data-active-target] {
  background-color: red;
}

.box.active, div[data-active-target].active {
  opacity: 1;
}