Rainbow Trail

// User settings

var trailLength = 200;

var segmentSize = 20;

var colorSpeed = 1;

var innerColorSpeed = 5;

​

// Global variables

var trail = [];

var h = 0;

​

function setup() {

  createCanvas(500, 500);

  colorMode(HSB);

  noStroke();

}

​

function draw() {

  background(255);

  trail.push({

    'x': mouseX,

    'y': mouseY

  });

  var thisColor = h;

  for (var i = 0; i < trail.length; i++) {

    fill(thisColor, 100, 100);

    var seg = trail[i];

    ellipse(seg.x, seg.y, segmentSize, segmentSize);

    thisColor = (thisColor + innerColorSpeed) % 360;

  }

​

  if (trail.length > trailLength) {

    trail.splice(0, max(trail.length - trailLength, 0));

  }

  h = (h + colorSpeed) % 360;

}