It's called clapping circle. I remember it was a souvenir of the CCTV children's channel's friend-seeking action before, named after the sound of clapping. Clap circle is easy to play. Straighten it into a straight circle, then pat it gently on your wrist with the back of the circle, and the circle will curl up on your wrist immediately according to the size of your hand.
I miss my childhood now. ......