Open the AudioManager.m file and add the following #define statements to define the keys we'll use to save and load the corresponding audio setting:

#define kSoundKey @"AudioManager_Sound"
#define kMusicKey @"AudioManager_Music"

Scroll down to the toggleSound method and add the code to save the sound setting at the end of the method, right after it's changed:

-(void)toggleSound
{
    _isSoundEnabled = !_isSoundEnabled;
    
    [[NSUserDefaults standardUserDefaults]
      setBool:_isSoundEnabled forKey:kSoundKey];
    
    [[NSUserDefaults standardUserDefaults]
      synchronize];
}

Also, add the code to save the music setting at the end of the toggleMusic method:

-(void)toggleMusic
{
    //..skipped..
    
    [...