a kinda cool thing (generative art) that I put into http://jelv.is/draw/

gistfile1.js

function (x, y, d, a) {
  function surface(x, y) { return (x-sin(y))*(sin(x)-y)*(sin(x)-sin(y)); }

  function safer(func) {
    return function(x) {
      if (x === 0) return 0;
      else if (x < 0) return -func(-x);
      else return func(x);
    }
  }

  var pi = 3.14159265;

  // scale x and y
  var width = 400, height = 400;
  x = x*4*pi/width;
  y = y*4*pi/height;

  var h = surface(x, y);
  var s = 0.5; //surface(0.23*sin(24*pi*safer(log, x)), y);
  var l = 0.5; //surface(x, 0.01*y + 0.46*sin(24*pi*y*safer(sqrt, y) + pi/2));
  // I get a black image if i use the s and l constructions commented out :(

  function hslToRgb(h, s, l){
    // this function is from http://mjijackson.com/2008/02/rgb-to-hsl-and-rgb-to-hsv-color-model-conversion-algorithms-in-javascript
    // modified to return a Color object
    var r, g, b;

    if(s == 0){
        r = g = b = l; // achromatic
    }else{
        function hue2rgb(p, q, t){
            if(t < 0) t += 1;
            if(t > 1) t -= 1;
            if(t < 1/6) return p + (q - p) * 6 * t;
            if(t < 1/2) return q;
            if(t < 2/3) return p + (q - p) * (2/3 - t) * 6;
            return p;
        }

        var q = l < 0.5 ? l * (1 + s) : l + s - l * s;
        var p = 2 * l - q;
        r = hue2rgb(p, q, h + 1/3);
        g = hue2rgb(p, q, h);
        b = hue2rgb(p, q, h - 1/3);
    }

    return new Color(r * 255, g * 255, b * 255);
  }

  return hslToRgb(h, s, l);
}