*[class*="rect-"] {
    position: relative;
    display: block;
    width: 100%;
    height: 0;
    overflow: hidden;
}
.rect-75 {
    padding-bottom: 75%;
}
.rect-100 {
    padding-bottom: 100%;
}
*[class*="rect-"] ._full {
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
}
.f5f5f5{background-color: #f5f5f5;}