Minichess

Minichess is a family of chess variants played with regular chess pieces and standard rules, but on a smaller board. The motivation for these variants is to make the game simpler and shorter than the standard chess. The first chess-like game implemented on a computer was a 6×6 chess variant Los Alamos chess. The low memory capacity of the early days computer required reduced board size and smaller number of pieces to make the game implementable on a computer.

Chess on a 3×3 board does not have any clearly defined starting position. However, it is a solved game: the outcome of every possible position is known. The best move for each side is known as well. The game was solved independently by Aloril in 2001 and by Kirill Kryukov in 2004. The solution by Kryukov is more complete, since it allows pawns to be placed everywhere, not only on second row as by Aloril. The longest checkmate on 3×3 board takes 16 moves. The number of legal positions is 304,545,552.

In 2009 Kryukov reported solving 3×4 chess. On this board there are 167,303,246,916 legal positions and the longest checkmate takes 43 moves.

In 1981 mathematician David Silverman suggested 4×4 chess variant shown on the diagram. The first player wins easily in this game (1. axb3+ Qxb3 2. cxb3+ Kxb3 (or 2...Kb4 3. bxc3 checkmate) 3. bxa3+ Kc4 4. Qa2 checkmate), so Silverman proposed a variant: Black can select a pawn, and White must make a first move with this pawn. However, in this case Black wins even more easily (select pawn b2, 1.bxa3 (or 1.bxc3) b2+ 2. Qxb2 Qxb2 checkmate). To make the variant more playable, Silverman finally proposed to insert a row between pawns and use the board 4×5. In this variant pawns can do double-move if target square is free.

Another chess variant on a 4×5 board, Microchess, was invented by Glimne in 1997. Castling is allowed in this variant.

There is also variant on a 4×8 board, Demi-chess, which was invented by Peter Krystufek in 1986. Castling is allowed in this variant.

A board needs to be five squares wide to contain all kinds of chess pieces on the first row. In 1969, Martin Gardner suggested a chess variant on 5×5 board in which all chess moves, including pawn double-move, en-passant capture as well as castling can be made. Later AISE (Associazione Italiana Scacchi Eterodossi, "Italian Heterodox Chess Association") abandoned pawn double-move and castling. The game was largely played in Italy (including by correspondence) and opening theory was developed. The statistics of the finished games is the following:

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