.flex-caption {
  width: 100%;
  padding: 2%;
  left: 0;
  bottom: 0;
  background:rgba(0, 0, 0,.7);
  color: #fff;
  text-shadow: 0 -1px 0 rgba(0,0,0,.3);
  font-size: 14px;
  line-height: 18px;
}

body{

  background-color: red;
}