Curious, why Mandarin only? Is there something about the language that makes it more feasible or more attractive to the business?. FWIW I would consider using something like this if it could teach Japanese.

We plan to expand to all languages (the only real limits are languages with enough training data for LLMs / TTS models, so all popular languages)

Mandarin is just first for us because:

1. Thomas was already learning it

2. We can talk to users in English

3. We have some native-speaking friends who helped early

4. Has excellent support in AI products (second only to English)