The content is invaluable, especially for a non-native speaker. However, the program is fragile in the extreme – just a tap which misses a popups close widget will send the app to its grave. The app has crashed dozens of times in its first hour of use. The section on positions is useless – one has little or no control of which "position" will be described next. The descriptions are minimalist, and convey less information than a simple stick-figure would. (The background image never changes as the popup description of a position does.) Just silly, reallly.