MattyQ

function matrixRain() {
  const canvas = document.createElement("canvas");
  canvas.width = window.innerWidth;
  canvas.height = window.innerHeight;
  canvas.style.position = "fixed";
  canvas.style.top = 0;
  canvas.style.left = 0;
  canvas.style.zIndex = -1;
  document.body.appendChild(canvas);