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

section {
  width: 100%;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
}

section:nth-child(1) {
  background-color: rgb(183, 183, 183);
}
section:nth-child(2) {
  background-color: rgb(0, 213, 255);
}
section:nth-child(3) {
  background-color: rgb(255, 0, 204);
}
section div {
  width: 100px;
  height: 100px;
}

section div.box-red {
  background-color: rgb(255, 0, 0);
  position: absolute;
  top: 10px;
  left: 40%;
  z-index: 2;
}

section div.box-yellow {
  background-color: yellow;
  position: absolute;
  z-index: 1;
  left: 35%;
  top: 15px;
}

section div.box-green {
  background-color: green;
  position: absolute;
  left: 30%;
  top: 20px;
}