// your mission: change the definition of the myRandom() function

// to return a random number---without using random() or

// Math.random(). The random number should be between 0 and 1.

//

// this function will be called to determine the brightness of

// pixels on the screen (continually displayed in order from

// left to right, top to bottom, several pixels per frame.)

//

// define other variables if you need to.

var state = 1;

function myRandom() {

  // adapted from http://excamera.com/sphinx/article-xorshift.html

  state ^= state << 13;

  state ^= state >> 17;

  state ^= state << 5;

  // javascript numbers overflow as negative, so map output to modulo

  // plus 0.5

  var ret = ((state % 100) / 200) + 0.5;

  return ret;

}

​

// ---

// try to keep the code below unchanged (unless you have a really

// clever idea).

// ---

var pos = 0;

var step = 8;

var randomCanvas;

function setup() { 

  pixelDensity(1);

  createCanvas(200, 200);

  randomCanvas = createGraphics(40, 40);

} 

​

function draw() {

  background(0);

  noSmooth();

  randomCanvas.loadPixels();

  for (var i = 0; i < step; i++) {

    var pxval = myRandom() * 255;

    for (var j = 0; j < 4; j++) {

        randomCanvas.pixels[pos+j] = pxval;

    }

    pos += 4;

    }

​

  if (pos > randomCanvas.width * randomCanvas.height * 4) {

    pos = 0;

  }

  randomCanvas.updatePixels();

  scale(5);

  image(randomCanvas, 0, 0);

}

​

​