The difference between analysis and design is that analysis is implementation independent and design is implementation dependent. During design you look at the the software architecture (principles and guidelines) and non-functional requirements. 

Here you work out HOW you present data and HOW you store and retrieve data.  Try to keep the analysis model intact, then the model can be re-used for different implementations.

An example of a design class:

This class is used for the fulfillment of requirement U001 (Undo/Redo possibility).

The next example shows the presentation layer of the Sudoku app. Together with the MVC-pattern it can help to clarify how the app has been constructed.