var canvas = document.createElement('canvas'), 

    c = canvas.getContext('2d'), 

    SIZE = 350;

canvas.width = SIZE;

canvas.height = SIZE;

document.body.appendChild(canvas);

c.fillStyle = 'black';

c.fillRect(0, 0, SIZE, SIZE);

c.fillStyle = 'white';

var spa = function(ts) {

  var r = 0, t =  0;

  var jitterX, jitterY, jitterT, jitterR;

  for (var i = 0; i < 100; i += 0.5) {

    t = ts + i / 15;

    r = i;

    jitterR = 5 + i / 5;

    jitterT = Math.random() * 2 * Math.PI;

    jitterX = Math.random() * jitterR * Math.sin(jitterT);

    jitterY = Math.random() * jitterR * Math.cos(jitterT);

    c.fillStyle = `hsl(${t / Math.PI * 180}deg, 50%, 50%)`;

    c.fillRect(

      SIZE / 2 + r * Math.cos(t) + jitterX,

      SIZE / 2 + r * Math.sin(t) + jitterY, 

      3, 3

    );

  }

}

spa(0);

spa(Math.PI);