Supernova needs the initial design data of the application - after all, the primary purpose of Supernova is to transform the design data to native components. We've decided to support the Sketch first, simply because it offers currently unmatched options and it is open format for the developers.
Supernova's importer does not import the design as it is, but runs it through multiple stages of optimization to ensure that it is imported as close to real application as possible. That means removing redundant layers, optimizing the grouping, flattening the components to become images and more.
Supernova supports version 4.0+ of Sketch, and most of its functionality, including symbols, gradients, masks and many many more. Don't hesitate to use whatever you want, it can handle it.
Supernova uses our own heavily optimized import engine that is both blazing fast and extremely precise, so it can handle dozens of the screens without breaking a sweat. It does not use network or cloud processing, everything runs locally on your machine, providing you with the highest possible security even for the most sensitive projects. Check it out.
Supernova large file import
Future plans note:
We are working to bring full support of more input format than just Sketch. At the end, our goal is to help everyone, and we don't want any designer or developer to feel left out just because of their choice to use a particular tool. Stay tuned for annoucements soon.