Prototyping is the iteration of the structure of an app. It involves mostly designers (to figure out what to do) and programmers (to figure out how to do it). Often there are technical constraints or something ‘doesn’t work’ very well when actually tested on device, there needs to be an iteration loop involving the designer and the programmer.
It is important to make multiple fundamentally different prototypes, and then to pick the most effective one. In our experience in the past, often a spec is created and implemented, however this this affects the quality of the final product since it is actually only a single prototype. There is a strong tendency to get locked in to an approach if only one approach is being examined, which will lead to medium to long term problems.
Development is the adding of art assets to the app, and fleshing out the app based on the prototype. It involves artists, programmers to create the app and designers to make sure the overall vision is being achieved. Once art assets are created, it becomes difficult to change things, so we should be careful on the timing of the creation of art assets.
Finally a polish phase can be useful, this is what brings the app from 90% to 100%. In general functionality does not change here. Polished graphics with Disney’s Illusion of Life, interactions that feel good and don’t hitch, short load times and gameplay tweaks.