.container {
  width: 500px;
  height: 400px;
  border: 1px solid #c3c3c3;
  display: flex;
  flex-direction: column;
  flex-wrap: wrap;
  justify-content: flex-start;
  align-content: flex-start;
}

.container > .child{
  width: 80px;
  height: 80px;
}