var canvas = document.createElement('canvas'),
    context = canvas.getContext('2d');

canvas.width = window.innerWidth;
canvas.height = window.innerHeight;

document.body.appendChild(canvas);

Particle.prototype.getPoint = function () {
  return {
    x: (this.current.radius * Math.cos(this.current.angle * Math.PI / 180)) + this.current.x - (this.current.w/2),
    y: (this.current.radius * Math.sin(this.current.angle * Math.PI / 180)) + this.current.y - (this.current.h/2)
  };
}

var particles = [];
for (var i = 0; i < 1000; i++) {
  particles.push(new Particle({
    x: window.innerWidth/2,
    y: window.innerHeight/2,
    w: Particle.prototype.random(1,3),
    h: Particle.prototype.random(1,3),
    radius: Particle.prototype.random(Math.random() < .4 ? 1 : 20,75),
    angle: Particle.prototype.random(0, 360),
    color: 'rgb(' + [Math.floor(Math.random() * 255),Math.floor(Math.random() * 255),Math.floor(Math.random() * 255)].join(',') + ')',
    minAngleDecay: Particle.prototype.random(10, 600)
  }));
}

var lastFrame = 0,
    fps = 60,
    start = Date.now();

function draw() {

  requestAnimationFrame(draw);

  var frame = Math.floor((Date.now() - start) / (1000/fps));
  if (lastFrame === frame) {
    return;
  }
  
  context.clearRect(0, 0, canvas.width, canvas.height);


  particles.forEach(function (particle) {
    if (Math.random() > .90 && (!particle.decay.angle || Math.floor(Math.abs(particle.decay.angle)) < particle.value.minAngleDecay)) {
      particle.decay.angle = particle.random(particle.value.minAngleDecay, 200);
    }
    
    if (Math.random() > .90 && (!particle.decay.radius || Math.floor(Math.abs(particle.decay.radius)) < 20)) {
      particle.decay.radius = particle.value.radius - particle.current.radius;
    }


    for (var i = 0; i < frame - lastFrame; i++) {
      particle.updateDecay(.97);
    }

    var point = particle.getPoint();
    context.fillStyle = particle.value.color;
    context.beginPath();
    context.arc(point.x, point.y, particle.current.w/2, 0, 2 * Math.PI, false);
    context.fill();
  });

  lastFrame = frame;
}

draw();

var mouseDownTime;
window.addEventListener('mousedown', function () {
  mouseDownTime = new Date();
});
window.addEventListener('mouseup', function () {
  particles.forEach(function (particle) {
    particle.decay.radius = particle.random(0, new Date() - mouseDownTime);
  });
});

window.addEventListener('mousemove', function (event) {
  particles.forEach(function (particle) {
    particle.decay.x = event.x - particle.current.x;
    particle.decay.y = event.y - particle.current.y;
  })
});