private void createBalls() {
        BodyDef ballBodyDef = new BodyDef();
        ballBodyDef.type = BodyDef.BodyType.DynamicBody;

        CircleShape shape = new CircleShape();
        shape.setRadius(10/Constants.PPM);
        shape.setPosition(new Vector2(w/4/ Constants.PPM, 5));

        FixtureDef fd = new FixtureDef();
        fd.density = 1;
        fd.friction = 0.5f;
        fd.restitution = 0.5f;
        fd.shape = shape;

        do {
            float rand = MathUtils.random(-2.0f, 2f);
            shape.setPosition(new Vector2(w/4/ Constants.PPM + rand, 5));
            fd.shape = shape;

            bodyArrayList.add(world.createBody(ballBodyDef));
            bodyArrayList.get(bodyArrayList.size() - 1).createFixture(fd);
        } while (bodyArrayList.size() < 100);

        shape.dispose();
    }