Scanlines

body::before {
    content: "";
    display: block;
    position: fixed;
    left: 0;
    top: 0;
    width: calc(100% + 32px);
    height: calc(100% + 32px);
    background-image: url("https://files.catbox.moe/lkk9y9.png");
    background-position: 0 0;
    background-repeat: repeat;
    z-index: 10000000;
    animation: ScanlineAnimationLeft 2s linear infinite;
    pointer-events: none;
    opacity: 0.75;
}

body::after {
    content: "";
    display: block;
    position: fixed;
    left: -32px;
    top: 0;
    width: calc(100% + 32px);
    height: calc(100% + 32px);
    background-image: url("https://files.catbox.moe/lkk9y9.png");
    background-position: 0 0;
    background-repeat: repeat;
    z-index: 10000000;
    animation: ScanlineAnimationRight 0.4s linear infinite;
    pointer-events: none;
    opacity: 0.75;
}

@keyframes ScanlineAnimationLeft {
    0% {
        transform: translateX(0px) translateY(0px);
    }
    100% {
        transform: translateX(-32px) translateY(-32px);
    }
}

@keyframes ScanlineAnimationRight {
    0% {
        transform: translateX(0px) translateY(0px);
    }
    100% {
        transform: translateX(32px) translateY(-32px);
    }
}