#how_to_play .web_app .btn {
    position: relative;
}
#how_to_play .web_app .btn::after {
    position: absolute;
    top: 0;
    left: 0;
    content: "";
    background-color: rgba(0, 0, 0, 0.5);
    display: block;
    width: 100%;
    height: 100%;
    border-radius: 16px;
}
@media print, screen and (max-width: 768px) {
    #how_to_play .web_app .btn::after {
        border-radius: 1.5vw;
    }
}