.box {
  display: flex;
  display: -webkit-flex;
  flex-wrap: wrap;
  flex-grow: 1;
  flex-shrink: 1;
  max-height: 700px;
  padding: 20px;
}
.box .item{
  width: 250px;
  height: 250px;
  max-width: 100vh;
  max-height: 100vh;
  padding: 10px;
}