touching Lava?test sprite contact
Public lesson / Scratch & Game Design
How Does the Game Know You Touched the Lava?
The floor looks extremely lava-like, but the computer does not care about appearances. What exactly counts as touching danger, and how often should the game check?
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 a sensing signal.
- Define a collision or boundary.
- Check a changing signal repeatedly.
- Prevent repeated scoring from one contact.
- Inspect collision evidence while debugging.
Theory kernel
Small examples before the larger build.
touching colour red?test a map region
distance to hazard < 40test nearness
if touching then set stateturn sensing into behaviour
Guided-build preview
The Floor Is Definitely Lava
Cross a room whose floor has become lava for reasons the building manager refuses to explain.
Horizontal movement, A controlled jump, Safe platforms, Lava collision.
Sensing, Collision, Coordinates, Variables, Game State.
A working version, one modification, one repaired problem, and an explanation.
Teacher checkpoints
Evidence before adding complexity.
- 1Student can show the collision area.
- 2Sensing is checked while movement occurs.
- 3One contact causes one state change.
- 4Restart clears the collision state.
- 5Student tests a fast boundary crossing.
Common mistakes
Pause, inspect, and test one cause.
- Costume transparency makes the hitbox surprising.
- Contact is checked only at startup.
- Score rises every frame during one collision.
- A visual overlap is assumed without reading the sensing result.
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 one safe platform.
Inventor
- Make platforms move while preserving collision.
Boss Level
- Create one-way or temporary safe surfaces.
End-of-class demonstration
Explain the work while it is still visible.
- What signal counts as contact?
- How often is it checked?
- What state changes?
- How did you test the boundary?
- What collision bug did you fix?