.popup .overlay 
{
    position: fixed;
    top: 0px;
    left: 0px;
    width: 100vw;
    height: 100vh;
    background: rgba(0, 0, 0, 0.7);
    z-index: 100;
    display: none;
}
.popup .content-mod {
    position: absolute;
    top: 35%;
    left: 50%;
    transform: translate(-50%, -50%) scale(0);
    background: #fff;
    width: 768px;
    height: 540px;
    z-index: 101;
    padding: 20px;
    box-sizing: border-box;
    border-radius: 10px;
}
.popup .close-btn {
    position: absolute;
    right: 20px;
    top: 20px;
    width: 30px;
    height: 30px;
    background: #6c6c6c;
    color: #fff;
    font-size: 30px;
    font-weight: 600;
    line-height: 30px;
    text-align: center;
    border-radius: 3px;
    cursor: pointer;
}

.popup.active .overlay {
    display: block;
}
.popup.popup.active .content-mod{
    transition: all 300mx ease-in-out;
    transform: translate(-50%, -50%) scale(1);
}