.demo-block {
    cursor: pointer;
    position: relative;
}

.demo-block > img {
    position: absolute;
    display: block;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    opacity: 1;
    transition: opacity 1s ease-in-out;
}

.demo-block:hover img.top {
    opacity: 0;
}

.demo-viewport .center-page-part  .demo-block-title-fs {
    color: #ffffff;
}