.preloader {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    
    transition: 1s;
    z-index: 99;
}
.preloader.complete:before {
    left: -50%;
}
.preloader.complete:after {
    right: -50%;
}
.preloader.complete {
    opacity: 0.7;
    visibility: hidden;
    pointer-events: none;
}
.preloader:before {
    content: '';
    position: absolute;
    left: 0;
    width: 50%;
    height: 100%;
    background: #000;
    transition: 1s;
}
.preloader:after {
    content: '';
    position: absolute;
    right: 0;
    width: 50%;
    height: 100%;
    background: #000;
    transition: 1s;
}