.container {
  display: flex;
  flex-direction: row;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-evenly;
}
.container div {
  background: yellow;
  border: 1px solid black;
  text-align: center;
  vertical-align: middle;
}
.regular {
  width: 200px;
  height: 200px;
}
.big {
  width: 300px;
  height: 300px;
}
.small {
  width: 100px;
  height: 100px;
}