div.stackPanel_vertical {
    /*border: solid thick red;*/
}

div.stackPanel_horzontal {
    /*border: solid thick blue;*/
}

div.content {
    padding: 10px;
    /*background-color: grey;*/
    margin: 10px;
    vertical-align: top;
    text-align: center;
}

div.stackPanel_horzontal > div.content {
    display: inline-block;
}

div.stackPanel_horzontal > div.stackPanel_vertical {
    display: inline-block;
}

div.stackPanel_horzontal.strech {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-around;
}