This is great. Foreign-language practice definitely seems like a great use case for LLMs. I'm surprised it understood your “你 dei tie ..." example, since "tie" is also valid pinyin.
Just for fun, I’m trying to force it to misinterpret what I’m saying by changing “dei tie” to “di tie” (as in subway). It really doesn’t want to interpret it differently! I think “shoelaces” must be such a strong signal of context for the LLM