A single number is often used to sum up how heavily a person leans on the planet. Today you turn your own week into four smaller numbers, then into a chart, and you test whether that big number was telling the whole story.

An ecological footprint is a rough measure of how much productive land and sea a way of living needs for food, materials, energy and dealing with waste. It is a model, not a moral score. A single total also hides the shape underneath: two people can share the same total while one uses most of it on travel and the other on food. The categories matter as much as the sum. Today's four categories are Travel, Food, Energy and Waste. You will score each one yourself, then show the pattern as a chart.

Score your typical week on the card for Travel, Food, Energy and Waste (each from 1 to 10). Add the four scores only after you have chosen them. Open the interactive activity and drag each bar to match your score. Sit with a partner and compare shapes first: where is each chart tall, and where is it low? Only then look at totals. Be ready if called to show a pair of charts with a similar total and a different shape, or a similar shape and a different total.

Look back at your four bars. Write two short lines only. Line one: the one category you could genuinely change in the next month, and why that one. Line two: the one category you could not honestly change much right now, and why. Be ready to read one of the lines if asked. No score is better or worse here; the point is to read your own chart honestly.

You can now say what an ecological footprint is trying to measure, and what a single total leaves out. You scored Travel, Food, Energy and Waste for a typical week, built a bar chart of that data, and used the shape of the chart to spot what a total alone would hide. You also named one category you could change and one you could not.