static string LoadText(string file){
NSUtils.Assert (file.EndsWith (".txt"), "Text file in Resources folder must be '*.txt' format!");
string ext = Path.GetExtension(file);
file = file.Replace (ext, "");
TextAsset asset = Resources.Load<TextAsset> (file);
NSUtils.Assert (asset!=null, "cocos2d: CCTmxParser:File not found :{0}.", file);
return asset.text;
}