var A = 1.8;

var B = 2.1;

var C = 1.8;

var D = -2.9;



var time;

var colors = [];



function setup() {

  createCanvas(windowWidth,

               windowHeight);

  background(0, 0, 0);

  noStroke();



  colors.push(color(50, 180, 250, 128));

  colors.push(color(100, 250, 250, 120));

  colors.push(color(225, 360, 225, 110));

  colors.push(color(455, 160, 135, 10));

  colors.push(color(200, 250, 70, 10));

  colors.push(color(35, 25, 515, 315));

  colors.push(color(265, 765, 893, 315));



  time = 0;

}



function draw() {

  translate(windowWidth / 2, windowHeight / 2);



  var x = random(-3, 10);

  var y = random(-7, 3);



  for (var i = 0; i < 2000; i++) {

    var xx = sin(A * y) - cos(B * x);

    var yy = sin(C * x) - cos(D * y);

    var c = getColor(time);

    fill(c);

    ellipse(xx * width * 0.25, yy * height * 0.25, 1);

    x = xx;

    y = yy;

  }



  time = time + 0.01;



  if (time > 1.0) {

    time = 0.0;

    C += 0.1;

  }

}



function getColor(t) {

  var p = t * (colors.length - 1);

  var from = floor(p);

  return lerpColor(colors[from], colors[from + 1], p - from);

}