I've tried to play a yes-no game with Form 12 students (3rd year of Ch). There were only two of them present, the best in the class. To my amazement, we spent 2 lessons speaking only Chinese! About different topics, chosen randomly from a list.

The y/n game was to guess an animal. A poster with animals was given to the ss for more ideas. Then we analyzed how good the questions they asked were. During the game it got clear that some criteria should be stated in the beginning.

Eg, on the poster a dog was black, and I didn't know what to answer to the question 'Is it brown?'. Like me, the ss floated from speaking about the animals on the poster and in general too... Also, questions can't be about subjective values, like 'Is it beautiful?'. A question which leads the game to a fast finish is 'Is is in the bottom part of the poster?'. Or maybe it's a good question??? :)

Yeah, I also wanted to play with 2nd year students, but after the holiday it became impossible, as I saw. So, I'm waiting for a more suitable moment. It's a really good exercise. And can be done for any topic.