$( document ).ready(function() {
  
  // Set canvas drawing surface
  var space = document.getElementById("surface");
  var surface = space.getContext("2d");
  var partState = "lighter";
  surface.scale(1,1);
 
   $('#changer').on('click', function() {
   if (partState==="xor"){
     partState="lighter";
   }else{
     partState="xor";
   }
  });
  
  // Set Particles
  var particles = [];
  var particle_count = 150;
  for(var i = 0; i < particle_count; i++) {
		particles.push(new particle());
	}
  var time = 0;
  // Set wrapper and canvas items size
  var canvasWidth=320;
  var canvasHeight=480;
  $(".wrapper").css({width:canvasWidth,height:canvasHeight});
  $("#surface").css({width:canvasWidth,height:canvasHeight});

  // shim layer with setTimeout fallback from Paul Irish
  window.requestAnimFrame = (function(){
    return  window.requestAnimationFrame       ||
            window.webkitRequestAnimationFrame ||
            window.mozRequestAnimationFrame    ||
            function( callback ){
              window.setTimeout(callback, 6000 / 60);
            };
  })(); 

  function particle() {
     
		this.speed = {x: -1+Math.random()*2, y: -5+Math.random()*5};
     canvasWidth = (document.getElementById("surface").width);
     canvasHeight= (document.getElementById("surface").height);
     this.location = {x: canvasWidth/2, y: (canvasHeight/2)+35};

		this.radius = .5+Math.random()*1;

		this.life = 10+Math.random()*10;
		this.death = this.life;
     if (partState==="lighter"){
		  this.r = 255;
		  this.g = Math.round(Math.random()*155);
		  this.b = 0;
     }else{
       this.r = Math.round(Math.random()*255);
		  this.g = Math.round(Math.random()*255);
		  this.b = Math.round(Math.random()*255); 
     }
	}
  
  function ParticleAnimation(){
		surface.globalCompositeOperation = "source-over";
		surface.fillStyle = "black";
		surface.fillRect(0, 0, canvasWidth, canvasHeight);
		surface.globalCompositeOperation = partState;
		
		for(var i = 0; i < particles.length; i++)
		{
			var p = particles[i];
			surface.beginPath();

			p.opacity = Math.round(p.death/p.life*100)/100
			var gradient = surface.createRadialGradient(p.location.x, p.location.y, 0, p.location.x, p.location.y, p.radius);
			gradient.addColorStop(0, "rgba("+p.r+", "+p.g+", "+p.b+", "+p.opacity+")");
			gradient.addColorStop(0.5, "rgba("+p.r+", "+p.g+", "+p.b+", "+p.opacity+")");
			gradient.addColorStop(1, "rgba("+p.r+", "+p.g+", "+p.b+", 0)");
			surface.fillStyle = gradient;
			surface.arc(p.location.x, p.location.y, p.radius, Math.PI*2, false);
			surface.fill();
			p.death--;
			p.radius++;
			p.location.x += (p.speed.x);
			p.location.y += (p.speed.y);
			
			if(p.death < 0 || p.radius < 0){
				particles[i] = new particle();
			}
		}

  requestAnimFrame(ParticleAnimation);

}

ParticleAnimation();

});