Video narration
Why can a backpack look fine and still feel uncomfortable, cramped, or impossible to organize? You start with the need, not a clever-looking object: carry what you need comfortably and keep it organized. Criteria are the goals-what success should look like. Constraints are the limits: cost, size, materials, time, and safety. Before the final version, build a prototype: a rough, inexpensive model you can try. Fill it with real school things, wear it, and test it against the criteria. Does it hold everything? Is it comfortable? Evidence, not a promising idea, shows what works. Then iterate: use what you learned to change the backpack and test again. Design is not having the best idea once. It is balancing goals and limits with evidence. Engineers turn a vague need into a design by defining criteria and constraints, building a prototype, testing it, and iterating.