.t-cover:before {
    content: '';
    display: block;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    left: 0;
    top: 0;
    position: absolute;
    z-index: 10;
}
.t-cover .t-container {
    z-index: 20;
}