Games where you don't know what they're up to
In most games, the goal is clear to everyone. You know what you have to do to win, and you also know what your opponents have to do to win. But there are some games where that's not entirely clear. In some games, players have secret goals and can score secret points. You could be in the middle of the game and not be at all sure whether or not you're winning. How do these games work and what makes them appealing?