set mood to 5give mood a starting value
Lesson / Scratch & Game Design
Where Does the Score Live?
The space pet insists it was fed, but the program has forgotten. Give its needs names, decide what changes them, and make every new game start with a clean memory.
Lesson plan
What must the pet remember?
Choose two changing needs and give each one a useful name.
Start, change, read
Set a value, update it from an event, and use it in a condition.
Build the pet
Add care actions, time-based change, and a visible state.
Break the reset
Create a stale value deliberately, then repair the initialization.
Follow one value
Show where a variable starts, what changes it, and which rule reads it.
Learning goals
- Give a variable a useful name.
- Set its starting value.
- Update it when a particular event occurs.
- Read it in a condition.
- Distinguish the stored value from its on-screen display.
Small examples
change mood by -1update mood over time
if mood < 2make a decision from the stored value
set game_state to PLAYINGrecord the current mode
Guided project
The Suspiciously Emotional Space Pet
Keep an alien pet fed, rested, and reasonably trusting. It remains suspicious of the snack button.
At least two changing needs, Actions that affect those needs, Visible mood or state, Time-based change.
Variables, State, Events, Conditions, Timers.
A working version with a tested change, one repaired problem, and a clear explanation.
Teacher checkpoints
- 1The variable name describes what it stores.
- 2Restarting restores the initial value.
- 3One event changes the value once.
- 4At least one condition reads the value.
- 5The student can explain the current state.
Common mistakes
- Variable never resets.
- Several scripts change the score unexpectedly.
- A display is hidden but the value remains.
- Text and number values are compared accidentally.
Optional challenges
Builder
- Add a second need such as energy.
Inventor
- Make needs affect each other.
Boss Level
- Create named pet states from several variables.
End-of-class demonstration
- What does the variable remember?
- Where is it initialized?
- Which event changes it?
- Which decision reads it?
- What state is active now?