lily
https://blog.duolingo.com/video-call/
https://youtu.be/vBjfn2Pb6DI
Duolingo Max
ユーザー向けの機能
難易度調整を自動で行う
https://www.youtube.com/watch?v=IdOO5G1vEYw&embeds_referring_euri=https%3A%2F%2Fduocon.duolingo.com%2F&source_ve_path=MjM4NTE