Everyone loves high quality icons. Even user interface designers, who work with sketches and wireframes. The problem is that popular prototyping tools produce mockups that don’t look so great. That’s why Castle created over three hundred design elements specifically for prototyping. A hand-crafted set of icons for mockups. You can assemble anything from them, from the mobile YouTube UI to a model WWII tank. The icon set is in good shape and ready to roll under the most democratic of licenses.