The steady stream of new UX prototyping software continues. Last week saw the widely praised release of Principle, an OS X app that allows users to design and animate anything from multi-screen flows to individual interactions and behaviors. It’s the brainchild of Daniel Hooper, a former Apple engineer who worked on core photography apps for iOS and OS X. Hooper left the Bay Area in 2014 and moved home to Atlanta, where he was able to focus on creating Principle as a small, independent concern. I asked him a few questions about the launch over email.