Abstract games
Chess, draughts, cribbage, bridge and many other traditional games are completely abstract in nature. Yes, sure, there is a theme in chess. There are two fighting armies facing each other in the battlefield, and it makes sense for the peasants, i.e. the pawns, forming the biggest part of the army and being the most dispensable - but it pretty tenuous when it comes to how these pieces move. Draughts, on the other hand, is a completely abstract game of course. Many traditional games have great depth and complexity, showing that there is no need for a theme in a good game. So let's explore this some more.