let y = 25;

function setup() {

  createCanvas(windowWidth, windowHeight);

}

​

function draw() {

  background(0);

  let widinc = 20;

  let heiinc = -20;

  let wed = 100;

  let hei = 200;

  while (x <= windowWidth) {

    let r = random(255);

    let g = 0;

    let b = random(255);

    fill(r, g, b);

    ellipse(x, y, wed, hei);

    wed += widinc;

    hei += heiinc;

    if (wed > 200 || wed < 100) {

      widinc *= -1;

    }

    if (hei < 100 || hei > 200) {

      heiinc *= -1;

    }

    x += 8;

  }

  y += 2;

  x = 0;

}

​