Criteria and constraints — Design, 11–13 years
A design must meet its purpose while working within limits such as size, cost, safety and materials.
Success has conditions
A criterion says what a successful design must do, such as hold ten pencils or be easy to open. A constraint is a limit it must obey, such as using only cardboard or costing less than five euros. Together they turn a vague wish into a target you can check.
Why use limits?
Real designers rarely have unlimited money, time, space or materials. Limits are not just obstacles: they help a team decide between ideas and explain why one solution is better for this situation. They also prevent a design from solving one problem while creating a bigger one.
Worked example: a desk organiser
The brief is to make a pencil organiser from one sheet of A4 card. Criteria: it must hold 12 pencils, stand for one minute and let a pencil be removed with one hand. Constraints: only one sheet, no glue and no piece taller than 12 cm. A folded tube may pass all four checks; a flat card cannot hold the pencils.
The trap: one perfect feature
A designer may make something very strong, then discover that it is too heavy or too expensive. That mistake makes sense because improving one visible quality feels like clear progress. Design is a balancing act: a solution must meet the important criteria together, not win at just one.
Where it appears
A bicycle helmet must protect your head, fit properly, stay on and remain affordable. A game designer also balances fun, clear rules, playing time and the number of pieces. At home, you use the same thinking when choosing a shelf that must hold books, fit a wall and stay within a budget.
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