The app, features a light and shapes visual search engine, a thematic rule reference, and provides revision tests as well as a 3D rendering for Colreg rules 20 to 31. For each rule, you can change the observation point on the 3D rendering view by a touch/drag action. The visual search engine gives you the ability to find any Colreg rule in seconds. The app is free with premium content, ad-free, and does not require an internet connection.