-(id) initWithId:(int)sceneId
{
    CCLOG(@"scene With id");
    if ((self = [super init]))
    {
     //All common initialization happens here..
     switch (sceneId) {
        case 1:
            [self loadFirstLevelData];
            break;
        case 2:
            [self loadSecondLevelData];
            break;
        default:
            [self loadSecondLevelData];
            break;
    }
    //Other common stuff..
    [self setUpCounters];
    [self setUpWeaponsMenu];
    [self scheduleUpdate];
    [self schedule:@selector(timerUpdate:) interval:1];
    InputLayerButtons* inputLayer = [InputLayerButtons node];
    [self addChild:inputLayer z:1 tag:GameSceneLayerTagInput];
}

E.g. FirstGameScene : GameScene

-(void) loadFirstLevelData{
//HERE WILL LOAD ALL SPECIFIC ELEMENTS: ENEMIES, BONUSES etc..

//AS WELL AS THE MUSIC FOR THE LEVEL
[[MusicLayer sharedMusicLayer] _loadMusic:@"1.mp3"];
[[MusicLayer sharedMusicLayer] playBackgroundMusicFile: @"1.mp3"];
}

-(void) cleanup
{
    //Should I remove all child loaded in LoadLevelData??
    CCLOG(@"cleanup GameScene");
    [[MusicLayer sharedMusicLayer] stopAllMusic];
    //MusicLayer is not a child of GameScene but of AppDelegate - the idea is to keep loading and unloading music files - sometimes I need to keep playing the file between scenes and hence I used the singleton pattern for this as well..
    [super cleanup];
}

#import "ShooterScene.h"
#import "LevelData.h"
#import "HudLayer.h"


@interface ShooterScene (PrivateMethods)
-(void) loadGameArtFile;
@end

@implementation ShooterScene

+ (id) sceneWithId:(int)sceneId
{
    CCScene *scene = [CCScene node];

    ShooterScene * shooterLayer = [ShooterScene node];
    [scene addChild:shooterLayer];
    [shooterLayer loadGameArtFile];

    LevelData * levelData = [LevelData node];
    [shooterLayer addChild:levelData];

    switch (sceneId) {
        case 1:
            [levelData loadLevelDataOne];
            break;
        case 2:
            [levelData loadLevelDataOne];
            break;
        default:
            break;
    }

    HudLayer * hud = [HudLayer node];
    [hud setUpPauseMenu];
    [shooterLayer addChild:hud];

    return scene;
}