ParserComp 2023: Xenophobic Opposites, Unite!

This is basically a followup to last year’s You Won’t Get Her Back by the same author. Once again, we have a chess problem with a light fiction wrapped around it. This time it’s about checkmating a lone king using just a king and two bishops, the bishop on white and the one on black being the “xenophoboc opposites” of the title, working together to pen the enemy in. I found it fairly easy to get the hang of herding the king around, but it gets difficult at the very end, where you have to get things positioned just right to avoid stalemate.

At first glance, the whole thing seems like just a slight variation on YWGHB, but on reflection, it’s more technically impressive. I commented before on how the position in YWGHB constrained the possibilities, cutting the game short whenever you made a mistake. This game is much freer, letting you play however you want and responding reasonably. It’s not a full-on chess engine — it only has to control one king! — but it’s clear that there’s a bit more than a look-up table in there, something it surfaces in the flavor text between moves, as the game acknowledges the enemy king’s increasing confinement and the bishops tut-tut at your mistakes.

ParserComp 2022: You Won’t Get Her Back

A chess problem, spiced with story. A king mourns the loss of his queen after his villainous opponent sacrificed his own queen to kill her, but he still has a loyal pawn who could possibly bring her back. (I don’t think the mechanics of chess quite fit the story here, since it’s possible to promote a pawn to a queen when the original queen is still on the board. But it kind of depends on whether the identity of the queen as a character is linked to its physical piece or its notional game object, and that’s really beyond the scope of the rules of chess.)

At any rate, the story here is really just flavor — while it does get reiterated during play, it isn’t extensive and doesn’t have a profound effect. No, the game is simply a chess problem, and the input is mainly a matter of making moves in “algebraic” chess notation. It’s not a large problem, giving each side just one piece other than the king, and it’s rendered smaller by the way that the game recognizes hopeless situations and cuts them short, in some cases before I personally understood that they were hopeless. Indeed, it’s so eager to do this that for a while I got the impression that there was only one allowable move from each position.

Apparently the problem is called the Saavedra Position, and it was thought that the best you could to is force a draw until Saavedra spotted a way to avoid stalemate through a clever underpromotion. It’s unlikely that I would have thought of this on my own if the game didn’t go to such pains to suggest underpromotion as a viable approach: a conspicuous portion of the help text discusses how to notate underpromotions, there are special commands for specifying what piece to promote pawns to by default, and even the title is a pretty big hint. I think that’s the main design takeaway here: how to direct the player by making them aware of possibilities.

IFComp 2012: Shuffling Around

Our next game is by one Ned Yompus, but I strongly suspect that this is a pseudonym, for reasons that will shortly become clear. Spoilers follow the break.

Read more »