Currently adding the Royal Game of Ur to DF. v0.47.05 for now.
But it's not just a game board item, I've got 1.6k lines of DFHack Lua (so far) to control boards being put in location chests, jobs for gathering game items, etc.
I'll require 4 tetrahedral dice (and assist the player with making them in fort mode), but for now it's just a game board item.
And I'm also actually simulating the game. Using code for the actual game itself and a move-picking agent (also all in Lua), units will actually make moves. It all happens in an instant for now, but I intend to do much more hacking to get them to play over time. I think I should also add a game log. Also, the skill of the move-picking agent is adjustable from 0% to 100%, where 100% isn't mathematical perfection (Ur is apparently solved), and that's based on the unit's analytical ability stat. The 100% skill agent isn't really all that skilled (though it does win against 0% (which makes an entirely random move each time) about 98% of the time), but I make it analyse its possible moves each turn and consider a few factors to determine the move's quality. I used my own crude code to optimise the weights for each factor over hundreds of thousands of games over 10 or so minutes. If I can, I might add the perfect move maker into the game so that a 2000 analytical ability unit is highly unlikely to win against any modded-in creatures with 6000 or whatever analytical ability.
The game could be played in advmode, but I haven't gotten to that point yet.
And, yes, I'm going to call the mod The Royal Game of Ur-ist, lol.
Image for now:

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Using otherwise-unattainable custom reactions for the job display. Since injecting reaction raws into a world seemed to break things (though items are fine), I also make it optional to have the reactions installed.
Also, the code works such that a third unit can gather the game pieces, though there's no trigger for this happening. It would be good for royalty tho! I'm imagining a "royal servant" entity position that can be generated when requirements are met, who sets up games between members of nobility. I don't play the default dwarf civ and have no royalty in my own civ but it'd be worth making.