Twenty Questions is the famous game where you will have to guess whats in other players mind in less than 20 simple yes or no questions.
You can create your own games and make them public to play with players around the world or invite your friends to play with you and dare them to guess whats in your mind.
There is a world and friends classification. You win more points solving the game with the less questions you can and beat your friends.
Just have fun guess or seeing how other peoples logic works to trying to solve your games.