when green flag clickedbegin from a known state
Public lesson / Scratch & Game Design
What Makes a Program Start?
A robot hamster receives five commands, but nobody tells it when to begin. Is the command list broken, or is the missing event the real problem?
Lesson rhythm
The idea moves toward a demonstration.
Story, problem, or provocation
Name the problem before opening the build.
Theory and concept
Make the hidden rule visible with small tests.
Guided build
Use the idea inside a working project system.
Modification challenge
Change one rule and predict the effect.
Demonstration and cleanup
Explain the result, save safely, and leave a known state.
Learning goals
What students should be able to do and explain.
- Identify an event and its response.
- Order commands intentionally.
- Predict a short sequence before running it.
- Separate setup from repeated behaviour.
- Explain one cause-and-effect link.
Theory kernel
Small examples before the larger build.
when space key pressedrespond to one input
broadcast STARTsignal another script
move / turn / waitcreate an ordered sequence
Guided-build preview
Robot Hamster Command Centre
Program a robot hamster to patrol snack storage without treating every crumb as an international emergency.
A grid-like map, Clear movement commands, A known start, A target route.
Events, Commands, Sequences, Coordinates, Messages.
A working version, one modification, one repaired problem, and an explanation.
Teacher checkpoints
Evidence before adding complexity.
- 1Student names the trigger.
- 2Student predicts a three-command sequence.
- 3Restart produces the same setup.
- 4One event has one clear responsibility.
- 5Student changes the order and explains the result.
Common mistakes
Pause, inspect, and test one cause.
- Code has no trigger.
- Setup runs after movement.
- Two events fight over the same output.
- The student changes timing without testing sequence order.
Modification challenge
Three levels, one concept kept visible.
Higher levels are optional. They deepen the current idea rather than turning a beginner lesson into an unrelated advanced task.
Builder
- Add a second command key.
Inventor
- Broadcast a mission-complete event.
Boss Level
- Build a queue of commands before execution.
End-of-class demonstration
Explain the work while it is still visible.
- What event starts the program?
- Which command runs first?
- What changed when the order changed?
- Which part is setup?
- What did you debug?