Team-Mate Chess

I generally try to avoid inventing new Chess variants, as there already are so many of them. So it is hard to make something that isn't just 'more of the same'.

As I love difficult pawnless end-games like KBNK, however, I could not resist the following idea: a variant where no single piece has the potential to checkmate a bare King, but where you would always need at least two pieces (+ your own King) to do that. And then have as many as possible different combinations that could do that. I call this variant 'Team-Mate Chess'.

So I made an initial setup of all different pieces (except for the usual King and Pawns), so you have 7 different non-royal types, and on top of that an 8th that you can only obtain by promotion. That makes 28 different possible pairs of unequal pieces. I picked the pieces such that of these 28 'teams', only a single one has no mating potential. That means there are 27 KBNK-like checkmates, where orthodox Chess only has one.

Of course there are also 8 pairs of equal pieces, but as you start with one of each you would only be able to get those through promotions, and like in Chess most pieces would virtually never been chosen. But for the record, only 2 of these 8 pairs have no mating potential (KNNK actually being one of those, as the Knight is one of the 8 participating piece types.)

The exact rules can be found at

http://www.chessvariants.org/index/msdisplay.php?itemid=MSteammatechess

I programmed Fairy-Max to play this variant, and this new version is already included in the pre-release of the WinBoard 4.8.0 install:

http://hgm.nubati.net/WinBoard-4.8.0.exe

It is able to find all the mates when playing against itself, at 40 moves/10 min. (I had to improve it for that, as originally it would not even be able to win KBNK. But it can do that too, now.)

This is on Winboard? It is not in my variant list? I was checking to see what other game rules I could aply to the custom.dat file. This check rule could be fun to add to a variant. Not that I fully understand what you were saying about it. Nor can I find it in winboard.

Fairy-Max plays it. It is an engine-defined variant, so WinBoard would not know about it without Fairy-Max being loaded as first engine. Just like WinBoard would not know about Alpha-Omega Chess (or 'custom') if p2p is not loaded (and you did not define the custom.dat file).

If you start WinBoard with Fairy-Max, Team-Mate Chess will appear in the New Variant menu. Together with Charge of the Light Brigade, King of the Hill, Bifurcator Chess, Ai-Wok and Rook-ASEAN, which are other engine-defined variants that Fairy-Max plays. Just like Mighty-Lion Chess and Werewolf Chess will appear there when you load HaChu, and Tori Shogi will appear there when you load Shokidoki.

There is no special check rule in Team-Mate Chess, btw. Just pieces without mating potential.