Chess is probably one of the most well-known board games in the world, with millions of players playing it around the world. There are two major divisions of chess: those that play chess as a game and those that play chess as a puzzle. Chess puzzles are further divided into two, tactical puzzles that are relevant for chess players and chess compositions that are rarely relevant for players, appealing for puzzle enthusiasts instead.
Above: Mate in 3, a tactical puzzle taken from some chess game
Above: Mate in 4, composed by Vincente Maria N. Portilla in 1873
Above: Helpmate in 8 (in helpmate, the two players cooperate to mate Black), composed by Z. Maslar in 1981
Chess compositions are divided into a large number of divisions (directmates and helpmates are two examples, shown above), but here I will talk about a quirky one, called retrograde analysis.
All you need to know are the rules of chess; you don't even need to know the strategies for playing chess, but you have to completely understand the rules. If you don't know the rules, turn back now and read that article until you completely understand it.
In retrograde analysis, you're not going forward in time...you're looking back in time.
Above: What was the last move? Composed by Ivan Koswara, 2014
You don't have to think about possible defenses like games and directmates; it's pure logic, much closer to a logic puzzle. Helpmates are similar.
Based on that sample puzzle above, do you find it interesting? Let me know!