Build a Scratch virtual pet with hunger and happiness

STEP 01

Draw your pet and two buttons.

Create a Pet sprite and two more sprites named Feed and Play. Paint the words on the buttons and keep them separate from the pet. Make two variables, Hunger and Happiness, for all sprites. Use a scale from 0 to 10: 0 hunger means full; 10 happiness means delighted.

STEP 02

Give the pet changing needs.

On Pet, build the following stack. The limits stop values growing beyond the scale. The pet is a simplified game character, not a model of real animal care.

when green flag clicked
set [Hunger] to (3)
set [Happiness] to (7)
forever
  wait (3) seconds
  if <(Hunger) < (10)> then
    change [Hunger] by (1)
  end
  if <(Happiness) > (0)> then
    change [Happiness] by (-1)
  end
end

STEP 03

Make the care buttons work.

On Feed: when this sprite clicked → broadcast feed. On Play: when this sprite clicked → broadcast play. Then add these two separate event stacks to Pet. Broadcasts let one sprite tell another that something happened.

when I receive [feed]
change [Hunger] by (-2)
if <(Hunger) < (0)> then
  set [Hunger] to (0)
end

when I receive [play]
change [Happiness] by (2)
if <(Happiness) > (10)> then
  set [Happiness] to (10)
end

STEP 04

Show how the pet feels.

Add a second green-flag stack to Pet. Inside forever, use if Hunger > 6 then say “Snack time?” else if Happiness < 4 then say “Let’s play!” else say “Hello, friend!” Use say without a seconds value, followed by wait 0.2 seconds. Choose which need gets priority and explain that choice. Add two costumes and switch them in these branches if you want a visual response.

STEP 05

Fix surprising behavior.

If clicking Feed does nothing, compare the broadcast and receive message names. If the values go outside 0–10, check the clamps are after each button update. If speech flickers, use one stack to choose the message instead of several stacks talking at once. Save the project to your computer.