* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Arial;
}

.header {
  text-align: center;
  padding: 32px;
}

.row {
  display: -ms-flexbox; /* IE10 */
  display: flex;
  -ms-flex-wrap: wrap; /* IE10 */
  flex-wrap: wrap;
  padding: 0 4px;
}
/* Mobile First Design - column of images */
.column {
  -ms-flex: 100%;
  flex: 100%;
  max-width: 100%;
}

.column img {
  margin-top: 8px;
  vertical-align: middle;
  width: 100%;
}
/* Responsive layout - makes the two columns  */
@media screen and (min-width: 600px) {
  .column {
    -ms-flex: 50%;
    flex: 50%;
    max-width: 50%;
  }
}

/* Responsive layout - makes a four column layout */
@media screen and (min-width: 800px) {
  /* Create four equal columns that sits next to each other */
  .column {
    -ms-flex: 25%; /* IE10 */
    flex: 25%;
    max-width: 25%;
    padding: 0 4px;
  }
}