var SpriteAnimation = new Class({

  Implements: [Options, Events, Loop],

    options: {
        frameWidth: 75,
        frames: 10,
        frameRate: 100,
        defaultPosition: {x: 0, y :0}
      },

  jQuery: 'spriteAnimation',

  initialize: function(selector, options){
    this.setOptions(options);
    this.setLoop(this.step, this.options.frameRate);
    this.element = jQuery(selector);
    var pos = this.options.defaultPosition.x + 'px ' + this.options.defaultPosition.y + 'px';
    this.element.css({'background-position': pos});
    this.startLoop();
  },

  step: function(){
    var x = this.computeX();
    var y = this.computeY();
    this.element.css({'background-position': x+'px '+ y+'px'});
    return this;
  },

  computeX: function(){
    this.loopCount = (this.loopCount == (this.options.frames)) ? this.options.defaultPosition.x : this.loopCount
    return -this.loopCount * this.options.frameWidth;
  },

  computeY: function(){
    return this.options.defaultPosition.y;
  }

});