Touch-move rule the player touches his rook at the same time as touching the king, he must castle with that rook if it is legal to do so. If the player completes a two-square king move without touching a rook, the player must move the correct rook accordingly if castling on that side is legal. Otherwise, the move must be withdrawn and another king move made. When a pawn is moved to its eighth , once the player takes his hand off the pawn, a different move of the pawn can no longer be substituted. However, the move is not complete until
Candidate move simply not capable of performing the complex pattern recognition that was required to find appropriate candidate moves, and that it was easier to have computers perform simple exhaustive searches. Today, most chess programs still rely mainly on brute-force searches, but as search algorithms have improved, today's chess engines seem more and more to be using candidate moves in their analysis. Hydra, for example, is widely considered to be a "Type B" (candidate move finding) computer. Candidate move In abstract strategy board games, candidate moves are moves which, upon initial observation of the position, seem to warrant further analysis. Although in