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This item is a game information page
It belongs to categories: Orthodox chess, 
It was last modified on: 2005-06-13
 By Fergus  Duniho. Caïssa Britannia. British themed variant with Lions, Unicorns, Dragons, Anglican Bishops, and a royal Queen. (10x10, Cells: 100) [All Comments] [Add Comment or Rating]
H. G. Muller wrote on 2016-10-08 UTC
files=10 ranks=10 holdingsType=1 promoZone=1 maxPromote=1 promoChoice=N*D*B*R*L*Q*U royal=9 graphicsDir=http://www.chessvariants.com/membergraphics/MSelven-chess/ whitePrefix=w blackPrefix=b graphicsType=png startShade=#4040E0 symmetry=mirror pawn::::a3-j3 knight:N::::10 dragon::DDAA::a1,j1 (anglican) bishop:B:BmW:bishop:d1,g1 prince consort::mQK:king:f1 rook::::b1,i1 lion::mQcpQ:cub:b2,i2 unicorn::BNN::c1,h1 royal Queen:Q:nQ:queen:e1

Caïssa Britannia

This very interesting variant contains some rather uncommon pieces, which made it a good candidate for the 'Diagram of the Week'.

Color coding of moves:

  • move or capture (sliding)
  • move or capture (jump)
  • non-capture only
  • capture only
  • moving into or passing through check

Passing through check

The most interesting aspect (and leading motive of the theme) here is of course the use of a powerful slider as royal piece. The brilliant idea of not allowing it to pass through check makes this work. Especially since you can pass through check to capture the opponent's royal. This fits with the interpretation that the Royal Queen can be taken en passant by any other piece, whenever she has made a multi-step move: if you use the multi-step move to capture the opponent's royal then you don't have to fear the e.p. retalliation, as the game is already finished.

This idea posed a challenge to the diagram, however, as originally this was made to display pseudo-legal moves. In this case that would be rather confusing. I could of course have switched it to displaying only fully legal moves, but this can sometimes be very confusing too, if you happen to click on a pinnend piece without realizing it, and only get to see part of the moves, those that stay on the pin ray.

So the solution I finally implemented is to keep showing pseudo-legal moves, except in the case of a royal. Then the diagram first calculates all pseudo-legal moves of the opponent (under the fiction that any target square would be occupied by a piece of us), and mark the thus attacked squares. Any move of our royal that would go to, or pass over such a marked square would then highlighted in gray. (Drag the Royal Queen to b6, and select it,to see what I mean.) Thus it still always shows you how the royal piece could move peudo-legally, but warns you about the passing through / into check. In orthodox Chess such a thing would only happen in the case of castling.