Expected result
Write down what should happen before editing.
Topic Guide
Debugging
Debugging begins with a precise difference: what should have happened, and what happened instead?
Why this matters
Guessing becomes expensive as a project grows. Students reproduce the problem, inspect a relevant value, choose one possible cause, and run a test that can prove them wrong.
Beyond this topic
If a bicycle chain slips only in one gear, that detail matters. A useful game bug report works the same way: it records the exact state and actions that produce the fault.
Math and logic
Observed result
Describe what happened, without adding a guessed cause.
Hypothesis
Name one possible explanation.
Controlled test
Inspect or change one thing that bears on that explanation.
Small examples
Show coordinates
Read x and y when movement goes wrong.
Display state
Check whether the game records PLAYING, WON, or LOST.
Test a smaller part
Run one sprite, sensor, or rule by itself.
Reproduce the bug
Find a sequence that makes the same problem happen again.
Program connections
Where this topic appears.
Active now
Scratch & Game Design
Students author games, animations, simulations, and strange interactive stories while learning how events, rules, and state fit together.
Active now
Robotics
Students write commands, wire simple circuits, read sensors, and trace physical cause and effect through the Sense–Decide–Act loop.
Coming later
Roblox Studio / Lua
A possible later step from visual programming into Lua, 3D objects, events, and larger game rules.
Coming later
AI & Smart Machines
A possible later program for testing patterns, predictions, prompts, mistakes, and the limits of AI tools.
Common mistakes
Editing several scripts
The bug disappears, but the useful evidence disappears with it.
Trying only the happy path
The centre of the stage works while the edge remains broken.
Blaming Scratch
A mistaken sign or state rule is left unexamined.
Covering the symptom
Extra blocks hide the fault without correcting the underlying value.
Put the idea to work
Scratch & Game Design
Guided Project
Escape from the Giant Pigeon
Build a fast chase game with known positions, collision rules, win and loss states, and reliable restart behaviour.
See how it works
Robotics
Guided Project
Robot Maze Logic
Write a robot route, predict where it will end, and trace the first command that goes wrong.
See how it works
Robotics
Guided Project
micro:bit Reaction Timer
Build a reaction timer with a random delay, an early-press rule, and results in the correct units.
See how it works