NOTE: This covers adding a new kind of pellet or a new kind of monster.  This is the most complicated cookbook item for the maze game.  Try to make adding additional objects to your maze a low priority.

ADD TO THE LAYOUT (OPEN MAZEGAMELAYOUT.PY):

In the layout class in the __init__ function, assign your new object to a number (the next available number is 5).  In my example, I'll add another type of pellet.

        self.SUPER_PELLET = 5

In the getLayout function, change the numbers in the grid to the number for your new object wherever you want your object to appear.  In my example, I would put some 5's in the grid to make some super pellets appear.

In the getSprites function, load an image for your new object and add it to the list that's returned on the last line.  The -1 will take out the background color in your object's picture, so that it doesn't have to be a square object.
        super_pellet, rect = load_image('superpellet.png',-1)
        return [space,pellet,block,player,monster,super_pellet]
        
CREATE A SPRITE CLASS FOR THE OBJECT (OPEN MAZEGAMESPRITES.PY):

Start by copying and pasting a similar object's class to the bottom of the file.  For example, if you are creating a new kind of monster, copy and paste the existing monster class.  Since I am creating a new kind of pellet, I will copy and paste the Pellet class.  Make changes to the new class based on how you want the object to be different.  The minimum changes will be the name of the class (Monster, Pellet, etc) and the default image that is used (monster.png, pellet.png, etc).

class SuperPellet(pygame.sprite.Sprite):
        
    def __init__(self, centerPoint, image = None):
        pygame.sprite.Sprite.__init__(self) 
        
        if image == None:
            self.image, self.rect = load_image('superpellet.png',-1)
        else:
            self.image = image
            self.rect = image.get_rect()
        self.rect.center = centerPoint

ADD THE SPRITE INTO THE GAME (OPEN MAZEGAME.PY):

Find the line 'space_sprites = pygame.sprite.Group()'.  Add a new line to create a group for your new objects.
For example: superpellet_sprites = pygame.sprite.RenderUpdates()

Find the following lines:
        elif layout[y][x]==level.FINISH_LINE:
            finish = FinishLine(centerPoint)
            finish_sprites.add(finish)
After these three lines (where it is checking the layout grid for a type of object and then adding sprites to the right groups), add a check for your new object type.  Change 'super pellet' in the following example to whatever your new object is called.
        elif layout[y][x]==level.SUPER_PELLET:
            super_pellet = SuperPellet(centerPoint)
            superpellet_sprites.add(super_pellet)

So that the player doesn't just run over your new object, you need to do something when the player is touching it.  Check for a collision between the two.  Add the line(s) you want to the main while loop.
To just erase the object and not do anything else: pygame.sprite.spritecollide(player, superpellet_sprites, True)
To erase the object and do something else:
   if len(pygame.sprite.spritecollide(player, superpellet_sprites, True)) > 0:
        game_over = True # replace this line with what you want to happen when they touch
To do something, and NOT erase the object:
   if len(pygame.sprite.spritecollide(player, superpellet_sprites, False)) > 0:
        game_over = True # replace this line with what you want to happen when they touch

Draw the new objects to the screen.  Add the following line after 'finish_sprites.draw(screen)':
     superpellet_sprites.draw(screen)