submission by QuietReads33 for make a scene using some motion (View the other submissions)
var y = 100;
var x = 100;
var a = 100;
var b = 100;

function setup(){
  var myCanvas = createCanvas(windowWidth,windowHeight); //you must keep this line unmodified
  stroke(200, 190, 255);
}
function draw() {
  background(5, 0, 20)
//I have no idea why they're off center sometimes
//I'm just happy I got the loop working properly
  y = y - 5
  x = x + 5
  a = a - 5
  b = b + 5

  if (y < 0) {
   y = height;
}
     line(0, y, width, y);

  if (x >800) {
   x = 0;
}

     line(0, x, width, x);

  if (a <0) {
   a = width;
}

    line(a, 0, a, height);

  if (b >800) {
   b = 0;
}

    line(b, 0, b, height);
}