* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
  list-style-type: none;
}

ul {
  width: 960px;
  margin: auto;
  padding: 100px 0;
  display: flex;
  flex-wrap: wrap;
}

li {
  width: 200px;
  height: 200px;
  text-align: center;
  line-height: 200px;
  /* outline: 1px solid red; */
  margin: 0 60px -40px;
  position: relative;
  font-size: 2rem;
}

li:before {
  content: "";
  position: absolute;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  /* outline: 1px solid #00f; */
  transform: rotate(45deg);
  z-index: -1;
}

li:nth-child(n + 4) {
  left: 160px;
}

li:nth-child(n + 7) {
  left: 0;
}

.box1::before {
  background-color: #ffadad;
}
.box2::before {
  background-color: #ffd6a5;
}
.box3::before {
  background-color: #fdffb6;
}
.box4::before {
  background-color: #caffbf;
}
.box5::before {
  background-color: #9bf6ff;
}
.box6::before {
  background-color: #a0c4ff;
}
.box7::before {
  background-color: #bdb2ff;
}
.box8::before {
  background-color: #ffc6ff;
}
.box9::before {
  background-color: #a5a5a5;
}

li:hover {
  color: #fff;
}

li:hover::before {
  background-color: #000;
}