p5js test

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.5.4/p5.min.js"></script>

CoffeeScript

var x=1

function setup() {
  createCanvas(400,400);
  noStroke();
  fill(0,255,0);
}

function draw() {
	background(240);
	rect(175,175,50,50);
	
	if (x=%1) {
		fill(255,0,0); 
	} else {
		fill(0,255,0);
	}
	
	x++
}

function mousePressed() {
  fill(255,0,0);
}

function mouseReleased() {
  fill(0,255,0);
}