The Chess Variant Pages



This page is written by the game's inventor, M Winther.

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H. G. Muller wrote on 2020-11-09 UTC

Indeed, the Snail has 5 moves, the Alpaca effectively has 5.33 moves. One should take care with asymmetric pieces, though: it is not only that captures and non-captures contribute different value; forward and backward moves also differ in importance. Also here the empirical evidence shows that forward moves contribute about twice as much as sideway or backward moves. So one could say the fD move represents 2/5 of the value of the D, rather than 1/4, and thus should be counted as 2/5 x 4 = 1.6 move. So the Snail effectively has 5.6 'move units'. The inverted piece, with a bD move, would only have 4.8, and would thus be significantly less valuable. This quantifies what Betza called 'forwardness'.

According to this calculation the Snail would thus be expected to be worth slightly more than the Alpaca. Otherwise the caveat holds that ZoG values are also just estimates, based on some unknown algorithm, and are very often completely off. But, as you can see in the piece table accompanying the diagram below, (by clicking the header of the 'move' column), the estimation algorithm of the Interactive Diagram actually agrees quite well with ZoG's estimate for the Alpaca/Knight ratio. And it assigns Snail and Alpaca practically equal values.

files=8 ranks=8 graphicsDir=/membergraphics/MSelven-chess/ whitePrefix=w blackPrefix=b graphicsType=png squareSize=34 useMarkers=1 maxPromote=1 promoChoice=QNRBAS symmetry=mirror enableAI=2 pawn::::a2,b2,c2,d3,e3,f2,g2,h2 alpaca::WmD:camel:d2 snail::WfD:tower:e2 knight:N:::b1,g1 bishop::::c1,f1 rook::::a1,h1 queen::::d1 king::::e1

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