Open HelloWorldScene.h and remove the menuCloseCallback method and unnecessary comments. Now HelloWorldScene.h should look like the following code:

 #ifndef __HELLOWORLD_SCENE_H__
   #define __HELLOWORLD_SCENE_H__
   #include "cocos2d.h" 

   class HelloWorld : public cocos2d::Layer
   { 
public:
    static cocos2d::Scene* createScene();
    virtual bool init();
    CREATE_FUNC(HelloWorld);
};
#endif // __HELLOWORLD_SCENE_H__

The next step is to open HelloWorldScene.cpp and remove unnecessary comments, codes, and methods. Now HelloWorldScene.cpp should look like the following code:

#include "HelloWorldScene.h"
USING_NS_CC; 
Scene* HelloWorld::createScene()
{
    auto scene = Scene::create();
    auto layer = HelloWorld::create();
    scene->addChild(layer);
    return scene;
} 
bool HelloWorld::init()
{
    if ( !Layer::init() )
    {
        return false;
    }
    return true;
}

The next step is to remove unnecessary images in resources. Remove CloseNormal.png, CloseSelected.png and HelloWorld.png from the Resources folder in Xcode:

Finally, if you are developing only iOS and Android applications, you don't need files for other platforms such as Linux, Windows, and Windows Phone. You should remove these files.

Before removing platform files, it should look like the following screenshot:

After removing platform files, it should look like the following screenshot: