let orig;

let tol = 0.0001;

let alp;

let p;

let pold;

let go = 1;

let n;

let C;

​

function setup() {

  alp = (3 - sqrt(5)) * PI;

  createCanvas(400, 400);

  pold = -1;

  p = createVector(0, r);

  orig = p.copy();

  background(220);

  n = 0;

  C = 2*sin(alp/2);

}

​

function draw() {

  if (go) {

    n++;

    push();

    translate(width / 2, height / 2);

    stroke(0);

    strokeWeight(0.5);

    noFill();

    ellipse(0, 0, 2 * r, 2 * r);

    p = rot(p, alp * 2.0);

    if (pold != -1)

      line(pold.x, pold.y, p.x, p.y);

    pop();

    pold = p.copy();

    if (p.copy().sub(orig).mag()<(tol*r)){

      go = 0;

      text((n).toFixed(0) + " bounces",20,20);

      text((n*C).toFixed(2) + " metres covered",20,40);

    }

  }

}

​

function rot(v, theta) {

  let vx = v.x * cos(theta) - v.y * sin(theta);

  let vy = v.x * sin(theta) + v.y * cos(theta);

  return createVector(vx, vy);

}