In my never-ending quest to be geeky in more ways than anyone else on the internet, I’ve invented a chess variant that incorporates the RPS dynamic while still (I hope) remaining playable. RPS is not only a game in its own right, and apparently one that some people take rather seriously (there’s also a 25-gesture version), but it’s a dynamic that appears in many other games. In wargames it’s often a range/mobility/defense triangle. For example, in a medieval wargame, long-range archers might be devastating against low-mobility infantry but vulnerable to high-mobility cavalry, while those cavalry in turn can’t get past the strong defense of massed infantry with pikes. Here’s how you apply the same idea to chess.

  • Paper = pawns. Rock = rooks and queens. Scissors = knights, bishops, and kings.
  • Members of every class can take other members of their own class, plus the next one in the circle. For example, a pawn can take another pawn, a rook or a queen, but not any of the “scissors” pieces.

What this does is make a lot of capture/recapture scenarios asymmetric. A pawn attacked by a knight and defended by a pawn is still vulnerable, because the pawn won’t be able to recapture the knight. This has some less obvious effects on strategy.

  • Some openings become much less effective. For example, Philidor doesn’t work because it’s an instance of the example above. On the other hand, Ruy Lopez still works because the pawn is defended by a knight, and Petroff still works because it’s more of a counterattack.
  • Bringing the queen out to b3 to attack b7 (one of my favorite motifs) is no longer as effective because the queen can’t take the pawn at b7. On the other hand, bringing the queen out to the king-side might be more effective because it can’t be harried by a knight. This also makes the fianchetto more risky, since the bishop won’t be able to defend a knight at c3/c6/f3/f6 that’s threatened by a queen.
  • A lone king is no longer helpless against two united passed pawns, because it can approach or capture the frontmost without being in check.

The last point I think is particularly important with respect to changing how endgames work, and how players maneuver to get a favorable one. At first I wasn’t wild about kings being so totally helpless against rooks and queens, but then I realized that such endings are generally a foregone conclusion anyway. They’re only tedious, not difficult, most of the time. Making them less tedious doesn’t seem like such a bad thing after all.

Some day when I have some spare time, I might take an existing chess program and modify its move generator to eliminate certain captures according to these rules. The position evaluator will be a bit askew, so the program won’t play strategy well, but most programs can beat me easily on tactics anyway so that’s unlikely to be an issue.