JSFiddle - React, Tailwind, and code Playground

HTML

<div class='v'></div>
<div class='h'></div>

CSS

.v, .h {
    position: fixed;
    background-color: red;
}

.v {
   top: 0px;
   bottom: 0px;
   width: 3px;
}

.h {
   left: 0px;
   right: 0px;
   height: 3px;
}

JavaScript

$(function(){
function sign(x) { return x > 0 ? 1 : x < 0 ? -1 : 0; }
var speed = 20;
var dx = speed * Math.random(), dy = speed * Math.random();
var $v = $('.v'), $h = $('.h');
var x = $h.offset().top, y = $v.offset().left;
setInterval(function(){
   if (x + dx > $(window).width()  || x + dx < 0)
       dx = -sign(dx) * speed * Math.random();
   if (y + dy > $(window).height() || y + dy < 0)
       dy = -sign(dy) * speed * Math.random();
   y = y + dy;
   x = x + dx;
   $h.offset({top:  y});
   $v.offset({left: x});    
}, 20);
});