body {
  display: flex;
  justify-content: center;
  height: 450px;
  align-items: center;
  opacity: 0.8;
}

#container {
  width: 500px;
  height: 400px;
  display: grid;
  border: 1px dotted black;
  grid-template-columns: repeat(3, 100px);
  grid-template-rows: repeat(2, 100px);

  /*   grid-auto-rows: 180px; */
}

.item {
  border: 1px solid black;
}

.item-1 {
  background-color: red;
}

.item-2 {
  background-color: orange;
}

.item-3 {
  background-color: yellow;
}

.item-4 {
  background-color: green;
}

.item-5 {
  background-color: blue;
}

.item-6 {
  background-color: violet;
}
.item-7 {
  background-color: black;
}