Some interesting things I could add to the tamagotchi programme which shouldn't be too hard:

• add pooping and cleaning function
• let it get sick if it's health is low, by random chance or if there's too much poop
• add sleep function, you have to switch the lights off otherwise it will have nightmare and loose one health point.
• add a function to restart the game or exit it after the pet died.
• add a function let the user exit the game
• safe the stats in a text file
• make a separate function for each age because it makes the aging function more readable
• add a function which lets the tamagotchi age (one week as a youngling, three weeks as an adult and two weeks as an elderly)