// number of sides gradually decreases to three

​

​

var cx, cy;

var radius;

​

//-----------------------------------------

function setup() {

  createCanvas(400, 400);

  radius = width / 2 * 0.75;

  cx = width / 2;

  cy = height / 2;

}

​

//-----------------------------------------

function draw() {

  background(255);

  noFill();

  stroke(0);

  strokeWeight(3);

​

  var maxSides = 60;

  var minSides = 3;

  var t = 0.5 + 0.5 * sin(millis() / 2000.0);

  t = pow(t, 0.33333);

  var nSidesf = constrain(map(t, 0, 1, maxSides, (minSides - 0.25)), minSides, maxSides);

  var nSidesi = ceil(nSidesf);

  var dang = TWO_PI / nSidesf;

  var ang = HALF_PI + (TWO_PI - (((nSidesi - 1) * dang))) / 2.0;

  if (nSidesi % 2 === 0) {

    ang -= dang / 2.0;

  }

​

  beginShape();

  for (var i = 0; i < nSidesi; i++) {

    var px = cx + radius * cos(ang);

    var py = cy + radius * sin(ang);

    vertex(px, py);

    ang += dang;

  }

  endShape(CLOSE);

}