Simple Javascript particle Generator

ParticleGen.js

/**
 *  
    options:(OBJECT){
        type : element type we're shooting.
        x : x coordinate
        y : y coordinate
        color : color of element
    }
*/
var ParticleGen = function(options) {
    var that = this;
    this.options = options;
    var elem = document.createElement(options.type);
    elem.style.left = options.x;
    elem.style.top = options.y;
    elem.style.width = '500px';
    elem.style.height = '10px';
    elem.style.background = '#cccccc';
    elem.style.position = 'absolute';
    document.body.appendChild(elem);
    this.move = function(el) {
        if (el.offsetLeft < (elem.offsetLeft + parseInt(elem.style.width) - parseInt(el.style.width))) {
            el.style.left = (el.offsetLeft *= 1.02) + 'px';
        }
    };
    return function() {
        window.setInterval(function() {
            var particle = document.createElement('div');
            particle.style.position = 'absolute';
            particle.style.background = '#0000ee';
            particle.style.height = '5px';
            particle.style.width = '10px';
            particle.style.left = elem.offsetLeft + 'px';
            particle.style.top = (elem.offsetTop) + 'px';
            document.body.appendChild(particle);
            window.setInterval(function() {
                that.move(particle);
            }, 20);

        }, 500);
    }();
};



/**
  Initializes a simple Particle generator which shoots divs across the screen. 
*/
var divgun = new ParticleGen({
    'x': '200px',
    'y': '200px',
    'color': '#aa0000',
    'type': 'div'
});