.mt-popup-mask {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.75);
    z-index: 9999;
    display: none; /* 默认隐藏，广告onLoad之后再改为flex显示 */
    align-items: center;
    justify-content: center;
}
.mt-popup-wrap {
    position: relative;
}
.mt-popup-close-btn {
    position: absolute;
    top: -32px;
    right: 0;
    background: #ffffff;
    color: #333;
    border: none;
    width: 28px;
    height: 28px;
    border-radius: 50%;
    font-size:16px;
    cursor: pointer;
    z-index:10;
}
.mt-countdown-tip{
    position:absolute;
    bottom:-28px;
    left:50%;
    transform:translateX(-50%);
    color:#fff;
    font-size:13px;
}