Cave Sentinel
I can scan, conditionally move, and confirm a safe stop at a barrier.
Your activities & worksheet
A crystal barrier blocks the tunnel. Scan before moving and show that the scout knows when to stop. Work with a partner, swap roles, and record your own thinking.
How does a fresh scan help a robot decide to stop?
Activity 1 · Investigate a scan
- Open Cave Sentinel. Try Move without Scan and read the feedback.
- Add Scan before Move. Predict and test how the current-position reading changes after moving.
Activity 2 · Build the safe scout
- Inside Repeat 4, add Scan, then IF path clear with Move in THEN.
- Add Confirm stop after the loop. Predict which checks skip movement, then complete the game.
Activity 3 · Explain the system
- Reset and run again, tracing scan input, IF processing, current scan storage, and movement/display output.
- Use the blocked case to explain why skipping Move is correct. Record an individual systems diagram.
Individual exit check
What should happen after the scout scans the barrier?
Teach this lesson
A 50-minute plan with preparation, prompts, model responses, differentiation, and an individual assessment.
How does a fresh scan help a robot decide to stop?
| Planning element | Teacher notes |
|---|---|
| Learning target | I can scan, conditionally move, and confirm a safe stop at a barrier. |
| Evidence of learning | Reach C3 R3, record a blocked scan, and confirm a safe stop. Keep individual predictions, observations, and an explanation; a completion badge alone does not establish mastery. |
| Standards focus | 2-3.CT.7, 2-3.CT.8, 2-3.NSD.1; 4-6.CT.7, 4-6.NSD.2 with a four-part systems model. |
| Vocabulary | sensor, input, condition, false, state, output |
| Readiness | Follow a short sequence and use a grid. Revisit the previous week’s prediction and explanation before introducing this game. |
| Preparation | Open game-week-04.html (Cave Sentinel). Check the four-legged cave scout and Crystal Sensor Cavern scene. Prepare a 5-by-5 grid, arrow counter, and worksheet. Use one device per pair and review the goal before revealing a solution. Game awards and worksheet responses save locally on this device; use teacher records for assessment. |
50-minute lesson sequence
| Minutes | Teaching moves | Look for |
|---|---|---|
| 0-5 | Introduce the mission Read the story and goal. Ask: How does a fresh scan help a robot decide to stop? Identify what must be observed to verify success. | Learners restate the task and constraints. |
| 5-12 | Model one action or test Demonstrate one control without solving the whole game. Explain the difference between robot heading and camera view. Ask for a prediction before clicking Run. | Each learner names an input, expected action, and observable result. |
| 12-20 | Activity 1: Investigate a scan Open Cave Sentinel. Try Move without Scan and read the feedback. Add Scan before Move. Predict and test how the current-position reading changes after moving. Ask pairs to trace with a counter before retesting. | Collect the first worksheet prediction and observation. |
| 20-35 | Activity 2: Build the safe scout Inside Repeat 4, add Scan, then IF path clear with Move in THEN. Add Confirm stop after the loop. Predict which checks skip movement, then complete the game. Swap driver and navigator after one run. Pause at the first unexpected state. | Both partners connect a block, label, or parameter with the observed result. |
| 35-43 | Activity 3: Explain the system Reset and run again, tracing scan input, IF processing, current scan storage, and movement/display output. Use the blocked case to explain why skipping Move is correct. Record an individual systems diagram. | A revision or comparison is supported by a recorded test. |
| 43-48 | Independent exit check Ask each learner: What should happen after the scout scans the barrier? Allow a spoken answer, drawing, or written response without a partner supplying the explanation. | Use the model answer as a guide; accept other explanations grounded in the run. |
| 48-50 | Save evidence and reflect Record completion and a next teaching step. Ask learners to download their worksheet or use a teacher-approved classroom record. | A next test or remaining limitation is named. |
Model program and expected behavior
repeat 4 { scan; if clear { move } }; confirm stopThe scout scans and moves twice to C3 R3. The next two scans are blocked by the barrier at C4 R3, so IF skips Move. Confirm stop records the decision using the blocked reading. A scan is required at the current pose before a move or IF check.
2D teaching reference
Columns run west to east; rows run north to south. S = start, G = goal, M = mission item, X = barrier, P = route. Start heading: east. Use counters and this grid as an alternative to interpreting the 3D view.
| Grid | C1 | C2 | C3 | C4 | C5 |
|---|---|---|---|---|---|
| R1 | . | . | . | . | . |
| R2 | . | . | . | . | . |
| R3 | S | P | G | X | P |
| R4 | . | . | . | . | . |
| R5 | . | . | . | . | . |
Misconceptions and a useful response
| Misconception | Response |
|---|---|
| A blocked IF is an error. | Point to the safe stopping tile. Compare skipping Move with trying to cross the barrier. The false condition is useful information. |
| Finishing the game proves I understand everything. | Ask for an individual prediction, trace, explanation, and a next test. Use completion as one piece of evidence. |
Differentiate the task
Support: Use clear/blocked cards and a tangible barrier. Offer the outer Repeat frame while learners choose scan and branch placement. Provide the written position/heading status and a 2D or tactile map when the 3D view is not useful.
Extend: Explain the stored reading and why a changed position or heading would make it stale. Recreate the probe in Scratch with explicit values.
Independent exit check
Prompt: What should happen after the scout scans the barrier?
Teacher key: The scan is blocked, so IF clear skips its move. Confirm stop records the decision at the safe tile.
Connect to Scratch or physical robotics
The simulation has ideal map-based sensing. Real distance sensors can be noisy, and a safe classroom robot needs a tested threshold and stop behavior.