let useTextOnly = false;

​

// let frames = 0;

let x, y;

let px = 0;

let py = 0;

​

let UNIT = -1;

​

let index = 1;

​

const dim = 50;

// 2500 frames

​

let step = 0;

let stepsWoutRotation = 0;

​

let rotation = 0;

​

function setup() {

  createCanvas(367*2, 367*2);

  fullscreen()

  background(0);

  x = width/2; y = height/2; // Initialize at center

  UNIT = (width/dim) * 1;

  textAlign(CENTER, CENTER);

  rectMode(CENTER);

  strokeWeight(UNIT/8)

  textSize(UNIT/2);

  px = x;

  py = y;

  const options = {

    units: "frames",

    delay: 0

  }

  // saveGif("noText.gif", 2500, options)

  // frameRate(2)

}

​

function draw() {

  // Draw

  if (isPrime(index)) {

    if (useText) {

      stroke(0,255,0)

      fill(0,255,0)

      rect(x, y, UNIT, UNIT)

    } else {

      fill(255)

      ellipse(x, y, UNIT/2, UNIT/2)

    }

  }

  // frames++;

    stroke(255)

  if (useText) {

    if (!useTextOnly)

      line(px, py, x, y)

    noStroke()

    fill(255)

    text(index, x, y);

  } else {

    line(px, py, x, y)

  }

  // Update

  px = x;

  py = y;

  index++;

  if (rotation == 0)

    x += UNIT;

  else if (rotation == 1) 

    y -= UNIT;

  else if (rotation == 2)

    x -= UNIT;

  else if (rotation == 3)

    y += UNIT

  if (rotation > 3) {

    rotation = 0;

    x += UNIT;

  }

  // Rotate

  if (stepsWoutRotation >= floor(step)) {

    stepsWoutRotation = 0;

    rotation++;

    step += 0.5;

    if (index > dim*dim) {

      noLoop()

    }

  } else {

    stepsWoutRotation++;

  }

  // console.log(frames)

}

​

function isPrime(num) {

  // Make it faster (because no even number except 2 is prime)

  if (num != 2 && num % 2 == 0) return false

  for (let i = 2; i <= sqrt(num); i++) {

    if (num % i == 0 && i != num) {

      return false;

    }

  }

  return true;

}