Time: 12–15 minutes
Materials: Vertical whiteboards, one marker per group, erasers. No technology.
Your café has hired a robot. It follows your instructions exactly—and cannot fill in missing steps.
The menu
| Item | Price | Starting stock |
|---|---|---|
| Cookie | $2 | 3 |
| Muffin | $3 | 2 |
| Juice | $2 | 4 |
Design it — 4 minutes
In your group of three, write instructions for taking and filling one customer’s order. Customers may request several items. Use plain language or pseudocode. Show how the robot keeps track of stock and calculates the total. Assume customers pay the exact amount.
Be the robot — 3 minutes
Move to another group’s board. Follow their instructions for an order of two cookies and one juice. Record the total and remaining stock. Mark any point where you have to guess.
Surprise — 3 minutes
Return to your board. The next customer orders two cookies—but only one remains. Decide what the café should do, then revise your instructions so the robot can handle it.
Compare — 2–5 minutes
Visit another board. What did that group make clearer? Which information changes during an order? Which rule should always remain true?
For the teacher
Form random groups of three and rotate the marker between rounds. Give the opening challenge orally and reveal the surprise after groups have tested their first instructions. Ask “Where would the robot need to guess?” and “Could your stock become negative?”
During consolidation, connect students’ work to variables, conditionals, and repetition from ICS3U. Finish with the ICS4U question: “Which information and actions belong together, and how could we keep another part of a program from changing stock incorrectly?” No formal object-oriented vocabulary is needed yet.