Mobile apps need to be designed and tested to scale to avoid surprises when actual human hands start operating the app. Designs crafted or presented on large monitors can be deceiving, because it’s hard to think in terms of two scales at the same time. Better to work at scale, and if possible even view key screens and simple prototypes on the device itself.
Following are some simple techniques for designing and testing with scale prototypes.
Index Card Prototypes
For a mobile smart phone app, a stack of 3×5 index cards will