body {
    position: relative;
}

.movie_blk {
    width: 100%;
    height: 100%;
    position: fixed;
    z-index: -1;
    filter: grayscale(100%); 
}
.movie_blk video {
    width: 100%;
    height: 100%;
    object-fit: cover;
    position: absolute;
    top: 0;
    left: 0;
}
.movie_blk p {
    font-size: 20px;
    padding: 20px;
    border-radius: 8px;
    background-color: rgba(255,255,255,0.7);
    position: absolute;
    top: 50%;
    left: 50%;
    z-index: 1;
    transform: translate(-50%,-50%);
}