let y = 400;     // y position

let r = 50;      // radius

let speedX = 0;  // speed in X

let speedY = 0;  // speed in Y

​

function setup() {

  createCanvas(600, 400);

}

​

function draw() {

  background('pink');

​

  // update position

  x = x + speedX;

  y = y + speedY;

​

  // make the ball bounce of walls

  if (x < r || x > width-r) {

    speedX = speedX * -1;

  }

  if (y > height-r) {

    speedY = speedY * -0.9;

    y = height-r;

  }

​

  // we hit the left edge

  if (x < r) {

    // check if we have an Arduino connected

    if (writer) {

      // send the signal

      writer.write("!");

    }

  }

​

  // make the ball be affected by gravity and drag

  speedY = speedY + 0.25;

  speedX = speedX * 0.99;

​

  ellipse(x, y, 2*r, 2*r);

}

​

function mouseClicked() {

  // add some random acceleration when we click the ball

  if (dist(mouseX, mouseY, x, y) < r) {

    print("Clicked the ball");

    speedX = random(-25, 25);

    speedY = random(-20, 20);

  }

}

​