Taken from my alt account @system32:

body::before {
  content: " ";
  display: block;
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  background: linear-gradient(rgb(120 255 120 / 30%) 50%, rgb(120 255 120 / 0%) 50%); /*replace the greenish computer terminal hue with whatever color you want*/
    background-size: auto;
  z-index: 2;
  background-size: 100% 2px, 3px 100%;
  pointer-events: none;
}

@eyra yea the CSS you provided is correct but I personally prefer to add a "size: auto" just for good measure