Basically, someone decides on something and everyone else can ask 20 questions to try and narrow down what it is.
E.g.
- Is it alive?
- No
- Is it an ore
- yes
- is it stone
- no
- is it iron
- yes
The thing could be anything from a name to a country, just please do things that people will be able to guess.
Ask me for a longer explanation if you need it
Okay, I’ve thought of something. Start guessing!