91 problems carry a well-researched plan

Some problems are too large, regulated, or expensive for a student team to build against — but a rigorous design proposal is a genuine contribution. That means digging into the constraints, interviewing the people involved, comparing approaches honestly, and producing a plan detailed enough that someone with resources could act on it. On big infrastructure, policy-entangled, or safety-critical problems, this kind of groundwork is often the most valuable thing a small team can add.