.row.display-flex {
  display: flex;
  flex-wrap: wrap;
}
.row.display-flex > [class*='col-'] {
  display: flex;
  flex-direction: column;
}

 /* not requied only for demo * */
.row [class*='col-'] {
  background-colo: #cceeee;
  background-clip: content-box;
}
.panel {
    height: 100%;
}