CIRCULAR LAB

For teachers

Teacher guide

CIRCULAR LAB is a short decision simulation for secondary-school students (ages 15–19). They take the role of a design team and redesign an everyday product. At each step they choose between options that all have a real advantage and a real cost, and they watch four indicators and a budget react. A mini-task – a short calculation, a sorting game or an experiment – makes one key idea concrete. The session ends with an interpreted result and discussion questions.

A sustainable product is not just made of recycled material. What decides is its whole life cycle – energy, lifetime, repairability, logistics and the end of its use.

Try a scenario Open score card

How the app works

Every scenario follows the same learning loop, so once you know one, you know them all.

1
Choose a scenario
Four scenarios are available: electric kettle, smartphone, textiles and beverage packaging. Each opens with a short brief and three learning goals. No login or set-up is needed.
2
Decide step by step
Six or seven steps follow the product’s life cycle: material, production, use, repair, end of life. Every step asks one question and offers three options. After choosing, a “Why it matters” box explains the consequence and shows how the choice moves the indicators.
3
Watch the indicators
Circularity, energy, durability and cost start at 50 and move with every decision. A budget of 1 000 model points limits what can be chosen, so the “greenest” option everywhere is never affordable.
4
Do the mini-task
One step in each scenario is not a choice but a task: a physics calculation, a sorting game or a riddle with an experiment. It never lowers the score – its purpose is to explain and to let students test an idea.
5
Read the result
The result page gives an overall rating with a verbal interpretation, the four indicators, a life-cycle diagram showing strong parts, trade-offs and weak spots, what went well and what could be improved, one key insight and discussion questions.
6
Reflect and document
Students can change any decision and compare designs, then open the score card: results, effort, a decision log and a short reflection, saved as a PDF to hand in. The teacher’s assessment goes on the same document.

Indicators and scoring

Students see four indicators and a budget change after every decision.

CircularityWeight 35%
Materials, repairability, reuse, recyclability.
A high value means: The design keeps materials in circulation.
EnergyWeight 25%
Energy in production and use, efficiency, energy losses.
A high value means: Little energy is wasted over the life of the product.
DurabilityWeight 25%
Robustness, serviceability, spare parts, software support.
A high value means: The product lasts long and can be repaired.
CostWeight 15%
Economic sustainability: purchase and running costs and the budget.
A high value means: The economics of the design are favourable.

Indicator	Weight	What it covers	A high value means
Circularity	35%	Materials, repairability, reuse, recyclability.	The design keeps materials in circulation.
Energy	25%	Energy in production and use, efficiency, energy losses.	Little energy is wasted over the life of the product.
Durability	25%	Robustness, serviceability, spare parts, software support.	The product lasts long and can be repaired.
Cost	15%	Economic sustainability: purchase and running costs and the budget.	The economics of the design are favourable.

The budget

Every option shows its cost in model points. The total budget is 1 000 points.
An option is locked only if choosing it would make it impossible to finish the remaining steps within the budget. A design can therefore always be completed.
Because the budget is limited, students must give something up. Ask them: “What did you sacrifice, and why?”

How the score is built

Each indicator is on a 0–100 scale, starts at 50 and is limited to 0–100. A higher value is always more favourable.
The overall rating weights the indicators: circularity 35%, energy 25%, durability 25%, cost 15%.
Verbal bands: 85–100 very balanced circular design; 70–84 strong design with some trade-offs; 55–69 partial improvement but still linear weaknesses; below 55 the product remains largely linear.
Strengths and improvements are based on how each choice compares with the other options in the same step, not on the raw score.
Answers in the mini-task never change the score. All numbers are didactically simplified model values, not a life-cycle assessment – tell students this openly. The physics relations themselves (such as Q = m · c · ΔT) are real.

The three kinds of mini-task

Each scenario has one step that is a task instead of a choice. It never changes the score.

Physics calculation

Electric kettle, Smartphone

The student picks the result from three options and confirms. A step-by-step solution follows, and every step has a “Why?” explanation. A wrong answer gives a hint and can be retried. The numbers depend on earlier choices (for example the efficiency of the heating element or the charger).

Teaches: Q = m · c · ΔT, converting joules to watt-hours, efficiency and losses; E = P · t and charging time.

Card sorting

Textiles

Six items from a wardrobe are sorted into four bins – repair, pass on, textile collection, mixed waste. An explanation appears after every card, and a summary at the end.

Teaches: The order of preference: repair, pass on, recycle, and only then throw away.

Riddle and experiment

Beverage packaging

Students first guess after how many refills a refillable bottle beats a single-use one. Then two sliders (number of refills, distance) show the impact live, and a mission asks them to find the distance at which refilling never pays off.

Teaches: A break-even point, and why weight and distance matter in transport.

Using it in class

Before the lesson

One device per pair is enough – a laptop, tablet or phone with a current browser and an internet connection. Nothing needs to be installed.
Try the scenario yourself first (about 5 minutes) and read its teacher summary.
Form pairs. Ask students to talk before each choice and to swap who operates the device at each step.
Optional: project the first decision step and go through it together, including the “Why it matters” box.
On shared computers, ask students to use “Clear my data” on the score card at the end (see privacy below).

While students work

There is no single right answer. Praise reasoning, not the highest score.
Encourage students to change a decision after seeing its effect – “Try different decisions” on the result page restarts from step 1 with the previous choices kept.
Ask students to design twice: once for the lowest cost, once for the highest circularity. Compare what changed.
Use the misconceptions listed in each scenario summary to prepare follow-up questions.

Suggested lesson flow (35 minutes)

5 min
Introduction
Start with a question, for example “What happens to a broken kettle or phone?” Introduce the linear and the circular model and the four indicators.
20 min
Work in the app
Pairs work through the scenario at their own pace. Walk around and ask “What are you giving up with this choice?” Faster pairs can try a second approach.
10 min
Discussion
Compare results across pairs (the cheapest design against the most circular one). Use the discussion questions from the result page or the teacher summary.

Other ways to run it

Short (20 min): One scenario, no score card. Finish with a single discussion question.
Double lesson (45–90 min): Two scenarios (for example kettle and textiles) with the score card and reflection at the end.
Jigsaw: Each pair works on a different scenario, then presents its key insight to the class.
Flipped / homework: Students complete a scenario at home and bring the score card as a PDF to the lesson.

Assessment

The score card collects results, approximate time on task, the number of decisions revisited, a decision log and a short written reflection.
Its teacher section offers a rubric (understanding of trade-offs, mini-task reasoning, effort and engagement, quality of reflection), a grade field, a comment and a signature line. You can fill it in on screen or by hand on the printout, or ignore it and grade in your own way.
Assess the reasoning behind the decisions rather than the number. A design with a lower score but a well-argued compromise can show better understanding.
Time on task and revisited decisions are indications of effort, not marks. Pauses longer than two minutes are not counted.

Privacy and technical notes

No accounts, no registration and no tracking. Progress and the student’s name stay in the browser tab and are never sent to a server.
The data disappears when the tab is closed. To keep a record, the student saves the score card as a PDF (Save as PDF / print).
On shared computers use “Clear my data” on the score card or “Start over” on a scenario before the next student.
The app works from a phone to a classroom projector, can be used with a keyboard, and respects reduced-motion settings.

Frequently asked questions

Is there a right answer?: No. Every option has a real trade-off, and different priorities lead to different valid designs. The aim is to experience and explain the trade-offs.
Why can’t students choose the best option everywhere?: That is the point of the budget. Real products are compromises between material, energy, price and lifetime.
Do wrong answers in the physics task lower the score?: No. A hint is shown, students can try again, and the full solution is always explained.
Can students go back and change decisions?: Yes, at any time with Back or the step numbers. The indicators update immediately.
How accurate are the numbers?: They are didactic model values for comparing options, not measurements. The physics relations used are real.
How much physics is needed?: Very little – one relation per scenario and simple unit conversions. Each step is explained.

Scenario summaries

Each scenario has a one-page teacher summary with learning goals, concepts, key insights, common misconceptions and discussion questions.

Every page can be saved as a PDF with “Print / save as PDF”.