a variant of chess, played against Leonhard Euler ❦ Basel 1707 – St. Petersburg 1783
A knight may continue its leap in the same direction across empty squares, as far as the board allows. Everything else is chess.
Promote the pawn to
Euler’s Knights changes one rule of chess. A knight may go on leaping in the same direction as long as the squares it lands on are empty: from b1 it may stop at c3, or continue to d5, or to e7 if c3 and d5 are clear. Fairy-chess composers call the piece a nightrider. It is worth a little less than a rook, it gives check from across the board, and it makes the opening far sharper than in the orthodox game, since each side’s knights reach the other’s second rank from their starting squares. The Rules control switches back to orthodox chess.
Leonhard Euler wrote one of the first mathematical treatments of a chess question, a paper on the knight’s tour presented to the Berlin Academy in 1759; the variant sends his knights on a tour of their own. The Euler you play here is a program in his name. It searches with iterative deepening and alpha-beta (principal variation search), a transposition table of a million entries, null-move pruning, late-move reductions, killer and history move ordering, and a quiescence search, and it judges positions with tables tapered between middlegame and endgame together with pawn-structure, bishop-pair, rook-file and king-shield terms.
Unlike von Kempelen’s celebrated chess automaton of 1770, which concealed a human player, this one calculates in earnest. Everything runs in this single file, so you can save it, open it anywhere, and rewrite any part of it.