Some parts were took from f00f, otherx are quite comm9n here (read: CRT scanlines) and the font part I made it myself. I then edited it (the CSS not the font part) so that the things that the font didn't apply to actually got the same font (what I made is pretty clear because of how I do the indentartions)

I doubt you want a DOS program tho (a la EDIT.COM)

@font-face {
	font-family: "msdos";
	src: url(/api/v0/util/ext/image?img=https://files.catbox.moe/q2s1gv.ttf);
}

body, button, input {
	font-family: "msdos";
	image-rendering: pixelated;
	--radius: 0;
}

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%);
    background-size: auto;
  z-index: 2;
  background-size: 100% 2px, 3px 100%;
  pointer-events: none;
}

.notification {
  background: inherit;
  color: inherit;
  font-size: inherit;
  font-family: inherit;
}

nav button::before, nav a::before, .card:not(:has(form)) button, .card:not(:has(form)) a.button {
  border-radius: 0;
}

.pillmenu {
  border: none;
  border-radius: 0;
  --radius: 0;
}

.card, .card-nest, .card-nest .card:last-child {
  border: none;
}