Designer Scott Savarie created this iOS app that lets you compose design comps entirely on your iPhone. At heart, Napkin is not too dissimilar from Project LayUp, the iPad app that I’ve been collaborating with Adobe on for the past year-plus. Or, at least, it shares some of the same goals: creating a touch-optimized interface that makes the design process viable on a mobile device.

Napkin is an impressive piece of work for a solo production—Savarie created it after taking a class called “iOS for Designers.” A Flash video of the interface in action at designwithnapkin.com demonstrates that it’s straightforward and intuitive to use.

Nevertheless, Napkin runs into the fundamental challenge of building productivity apps on touch devices: the absence of a keyboard and mouse can significantly impede task completion. That core problem has consumed tons of design and development cycles for LayUp; it took lots of trial and error with simplified tools and controls before we realized that a drawing engine was necessary to allow touch manipulation to keep pace with a designer’s brain. It’s not an exact replacement for a keyboard and mouse, but for some aspects of the design process drawing the elements that you want to work with and having them instantly translated into live objects can be liberating. I’m looking forward to getting LayUp into lots of people’s hands so they can see for themselves if it works or not.