.alert {
    display: none;
    position: fixed;
    z-index: 9998;
    left: 0;
    right: 0;
    bottom: 0;
    top: 0;
    background: rgba(0, 0, 0, 0.8);
}

.alert video {
    position: fixed;
    z-index: 9999;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    display: block;
    width: 14.82rem;
    object-fit: cover;
}

.alert .cheng {
    display: block;
    position: fixed;
    top: 0.36rem;
    right: 0.68rem;
    font-size: 0.26rem;
    color: #fff;
    cursor: pointer;
}
@media only screen and (max-width: 768px) {
.alert video {
    width: 80%;
    left: 10%
    top: 60%;;
}    
    
}