let x = 0;

let y;

​

function setup() {

  createCanvas(400, 400);

  y = height;

}

​

function draw() {

  background(20);

  let b = map(x, 0, width, 0, 255);

  fill(x, x, x);

  ellipse(x, y, 50);

  x = (x+1) % (height/(x%3 ));

  y -= 1;

​

}

​

function backAndForth(current) {

  if (x>=397)

    {

      x/=1.01;

      return x;

    }

  else

    {

      x*=1.01;

      return x;

    }

}

​