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The Chess Variant Pages

O/R Chess - Overloader/Restorer chess


The standard rules of co-Chess apply, except where explicitly stated as otherwise so.

    The standard rules of Co-chess are:

  1. The standard rules of chess apply except where stated.
  2. In co-chess, each pair of identical pieces of the same colour (excluding pawns) forms a co-pair.
    Kings also form co-pairs with queens.
    Promoted pieces allow multipairing.
  3. Whenever one member of a co-pair moves to a square not on the same rank or file as the other, the co-pair defines two co-squares, each on the same rank as one of the pieces and the same file as the other.
    Only a moving piece can form co-squares.
    Castling is both a king move and a rook move, so both pieces can form co-squares thereby.
  4. Any piece on a co-square is subject to a co-effect.
    The nature of the co-effect defines the game being played.
    Co-effects are mandatory.
    Co-effects last only a single move.
    Pawn promotion cannot cause co-effects.
    Castling into check is permitted if the check is removed by means of the co-effect.
  1. There are two complementary co-effects in O/R Chess.
    1. An enemy piece on a co-square is overloaded: it loses all power except non-special moves.
      That is, it can move but not capture, check, promote, castle, act as part of a co-pair, or (if it is a pawn) make a 2-step move from the second rank.
    2. A friendly piece on a co-square is unaffected unless it has been overloaded.
      An overloaded friendly piece is restored: it returns to normal, regaining all its former abilities.
      Restoring an overloaded 8th-rank pawn causes it to promote at once.
  2. Overloading the enemy king does not win.

Sample game

Francis Fahys (France)-Alessandro Castelli (Italia), Grand Prix 1991, 0-1
1.e4 e5 2.Nf3 Nc6 3.Bb5 Bc5 4.00 d6 5.d4 B:d4 6.B:c6+ b:c6 7.N:d4 e:d4 8.Q:d4 Qf6 9.Qc4 Ne7 10.Nc3 Qh4/e4?? 11.Kh1/Qh4
The black Queen is overloaded.
11. ... Rb8 12.Bg5 (Q)g4 13.B:e7 Bd7
If 13. ... K:e7 14.Q:c6 e.g. 14. ... Kd8 15.Qa8/Rh8 and White wins.
14.(P)e5 ?
Better for White to save the Be7.
14. ... K:e7 15.Rab1 (Q)e6 16.f4 f5 17.Ne2 Rb618.Nd4 (Q)d5 19.(P)e6 g6 20.b4 Rd8 21.a4? Rb5/Qd5!
The black Queen is restored.
22.Qc3 Rb7 23.Qd3 Rdb8 24.c4 Qe4 25.Qd2? Kd8/Nd4 26.Rf2? R:b4!!
If 26. ... Q:b1+? 27.Qb2/Qb1..
27.R:b4? Qc2/Qd2! 28.Resigns
If 28.R:b8+ Qb1/Rb8 mate.

Written by: Alessandro Castelli (email removed contact us for address)
WWW page created: September 30, 1996. Last modified: June 25, 1998.