.shmu-box {
    position: relative;
}

.shmu-box:before {
    float: left;
    padding-top: 100%; /* 1 : 1 */
    content: '';
}

.shmu-box.shmu-box-wide:before {
    padding-top: 56.25%; /* 16 : 9 */
}

.shmu-box.shmu-box-wide-31:before {
    padding-top: 33.33%; /* 3 : 1 */
}

.shmu-box.shmu-box-wide-43:before {
    padding-top: 75%; /* 4 : 3 */
}

.shmu-box:after {
    display: table;
    clear: both;
    content: '';
}

.shmu-box .shmu-box-content {
    position: absolute;
    width: 100%;
    height: 100%;
}