.bg-text {
    padding: 20px 20px 40px 20px;
    position: relative;
    width: 400px;
    overflow: hidden;
}
.bg-text::after {
    color: #aaa;
    font: 1.2em "Fira Sans", sans-serif;
    content: attr(data-bg-text);
    display: block;
    font-size: 1200%;
    line-height: 1;
    position: absolute;
    bottom: -15px;
    left: 10px;
    z-index: -1;
    -webkit-mask-image: linear-gradient(to right, #000 50%, transparent);
}