It was not clear how having a tangible multiple-choice language learning tool is much better than a simpler touch-screen-based interface.  Moving marbles may be more fun than just touching a screen, but we were not sure that it's worth the added complexity that is required.  If you choose to continue with the language-learning for adults theme for your final project, you might want to consider attacking the problem from a different direction.  A couple of possibilities include: (1) supporting learning "on the go" or during down times, perhaps through a mobile phone interface (although this may not result in a TUI), (2) supporting connections between learners, e.g. between a solitary adult in the US trying to learn French and a solitary adult in France trying to learn English.