​

function setup() {

  createCanvas(windowWidth, windowHeight);

  x = width/2;

  y = 0;

  rad = 25;

  velocity = 1;

}

​

function draw() {

  background(245, 245,255);

  fill(0, 0, 255);

  noStroke();

  ellipse(x, y, rad*2, rad*2);

  y = y + velocity;

  velocity += 0.2;

  if ((y + rad) >= height) {

    y = 0-rad;

  }

  if (y < 0) {

    velocity = 1;

  }

}