function TweenEngine(){
	this.executionInterval = 33;
	this.curIndex = 0;
	this.commandQueue = [];
	this.isRunning = false;
}
TweenEngine.prototype.startEngine = function(method,obj,params){
	this.isRunning = true;
	this.intervalId=setInterval(this,"runNextCommand",this.executionInterval);
	return true;
}
TweenEngine.prototype.stopEngine = function(){
	this.isRunning = false;
	if(this.intervalId!=undefined){
		clearInterval(this.intervalId);
		return delete this.intervalId;
	}
	else return false;
}
TweenEngine.prototype.addCommand = function(meth,obj,params){
	this.commandQueue.push({meth: meth, obj: obj, params: params});
	return true;
}
TweenEngine.prototype.addCommands = function(commands){
	this.commandQueue = this.commandQueue.concat(commands);
	return true;
}
TweenEngine.prototype.setExecutionInterval = function(interval){
	this.executionInterval = interval;
	if(this.isRunning){
		this.stopEngine();
		this.startEngine();
		return true;
	}else{
		return true;
	}
}
TweenEngine.prototype.runNextCommand = function(){
	var cmd;
	var rtn = false;
	cmd = this.commandQueue[this.curIndex];
	rtn = cmd.obj[cmd.meth].apply(cmd.obj,cmd.params);
	if(!rtn) this.curIndex++;
	if(this.curIndex >= this.commandQueue.length) {
		this.curIndex = 0;
		if(this.isRunning)this.stopEngine();
		return false;
	}	
	return true;
}