# Phase 4: Prototype
After another pitch practice to rally the troops, there are no exercises in this phase. It is entirely focused on building the right prototype(s) with just the right amount of fidelity to generate useful test results.
For the entire phase, we ask our clients to write copy text in Google Docs. They write real text, not lorem ipsum, in order to test user understanding and enthusiasm. This text is also useful later for tweets, press, ad copy, landing pages, etc.
While our clients are busy getting communication polished, we are heads-down prototyping. We use different tools depending on the designer and the project.
For web app prototypes, some good options are:
For mobile app prototypes, some good options are:
Don't try to learn these tools during the sprint. Get familiar with them during investment time. During the sprint, use one that you've mastered.