Dan Shiffman - Mandelbrot Extra sliders

var colval = 4;
var maxval = 3;
var iterations = 4;
var xminSlider;
var xmaxSlider;
var yminSlider;
var ymaxSlider;
var bailout;
var iterslider;
var colslider;
var frDiv;

function setup() {
  createCanvas(200, 200);
  pixelDensity(1);

  xminSlider = createSlider(-maxval, maxval, 1.45, 0.01);
  xmaxSlider = createSlider(-maxval, maxval, -2.45, 0.01);
  yminSlider = createSlider(-maxval, maxval, -1.85, 0.01);
  ymaxSlider = createSlider(-maxval, maxval, 1.85, 0.01);
  bailout = createSlider(1, 32, 16, 1);
  iterslider = createSlider(iterations, iterations * 32, 24, 1);
  colslider = createSlider(0, 256, 16, 4);
  frDiv = createDiv();
}

function draw() {
  loadPixels();
  for (var x = 0; x < width; x++) {
    for (var y = 0; y < height; y++) {

      var a = map(x, 0, width, xminSlider.value(), xmaxSlider.value());
      var b = map(y, 0, height, yminSlider.value(), ymaxSlider.value());
      var ca = a;
      var cb = b;
      var n = 0;

      while (n < iterslider.value()) {
        var aa = a * a - b * b;
        var bb = 2 * a * b;
        a = aa + ca;
        b = bb + cb;
        if (a * a + b * b > bailout.value()) {
          break;
        }
        n++;
      }

      var bright = map(n, 0, colslider.value(), 0, 1);
      bright = map(sqrt(bright), 0, 1, 0, 255);
      if (n == iterslider.value()) {
        bright = 0;
      }
      var pix = (x + y * width) * 4;
      pixels[pix + 0] = bright % 4 * 64;
      pixels[pix + 1] = bright % 8 * 32;
      pixels[pix + 2] = bright % 16 * 16;
      pixels[pix + 3] = 255;
    }
  }
  updatePixels();
  frDiv.html(floor(frameRate()));
}