Create a new group called Common.

Right-click on this group and click on New File; it will be Objective-C class. Name it GameStats and make it a subclass of NSObject. Save the file.

Open the GameStats.h file and add the following properties:

@property (nonatomic, assign) int score;
@property (nonatomic, assign) int birdsLeft;
@property (nonatomic, assign) int lives;

Then open the GameStats.m file and add the init method:

-(instancetype)init
{
    if (self = [super init])
    {
        self.score = 0;
        self.birdsLeft = 0;
        self.lives = 0;
    }
    
    return self;
}

Open the HUDLayer.h file and import the GameStats.h header at the top, like this:

#import "GameStats.h"

Then add the following method declaration:

-(void)updateStats:(GameStats *)stats;

Switch to the HUDLayer.m file and add the implementation of this method below the init method:

-(void)updateStats...