let speed = 0;

let drag = 0.97;

let diameter = 50;

let x;

let y;

​

function setup() {

  createCanvas(640, 360);

  x = width / 2;

  y = 0;

}

​

function draw() {

  background(150);

  ellipse(x, y, diameter, diameter);

​

  speed += gravity;

  speed *= drag;

​

  y += speed;

​

  if (y > height - diameter / 2) {

    speed *= -1;

    y = height - diameter / 2;

  }

}

​