put this part in your css

/********* scanlines **********/

body::before{
    content: "";
    display: block;
    position: fixed;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
    background: linear-gradient(rgba(20, 20, 40, 0) 66%, rgba(0, 0, 0, 0.20) 33%);
    background-size: 100% calc(3px * var(--toggle));
    z-index: 9999;
    pointer-events: none;

    animation: scanlines-anim 0.7s linear infinite;
        animation-play-state: var(--playState);
}

@keyframes scanlines-anim{
    0% {
		background-position: 0px 0px;
	}
	100% {
        background-position: 0px 9px;
	}
}


@media {
    /********* scanlines **********/
    body::before{
        background-size: 100% 5px;
    }
}