I think of application design when I'm drawing screens. I feel I design an application when I'm thinking about what will be part of the Model, what will be part of the Controller and what Views will be required in order to display things to the users. I'm designing an application when I start to list the open source modules and framework that will be needed in order to save development time. I'm designing an application when I start to look for application icons. I'm building an iPhone application when I'm building the list of features that will be part of the initial release and all the subsequent releases. Yes, I feel that I'm into something when and I'm looking back into previous WWDC videos I order to remember how to write code.