Shogi

将棋

Japanese chess · captured pieces change sides

Setting up…

☗YouBlack · moves first

☖ComputerWhite

Opponent

Level

Handicap (駒落ち)

Japanese notation (７六歩) Mark the last move

Moves

Rules

The board is 9×9 and every piece faces the opponent. Black (☗, sente) moves first; the two sides use the same pieces, and which way a piece points is what tells you whose it is.
Setup. On the rank nearest you: king in the centre file, a gold general either side of it, a silver beyond each gold, a knight beyond each silver, and a lance in each corner — 香桂銀金玉金銀桂香. On the second rank the bishop goes in the left knight's file and the rook in the right knight's file. Nine pawns fill the third rank.
Capturing changes sides. A captured piece goes into your hand, and instead of moving you may drop it back on any empty square as your own — unpromoted, and facing your way. This is what makes shogi shogi: nothing is ever off the board for long.
Drops have three limits. Never two unpromoted pawns in the same file (nifu); never a piece where it could never move again (a pawn or lance on the last rank, a knight on the last two); and never a pawn dropped to give immediate checkmate (uchifuzume) — though a pawn already on the board may mate, and any other piece may be dropped to mate.
Promotion. The far three ranks are the promotion zone. Moving into, out of or inside it, a piece may turn over — pawn, lance, knight and silver all become gold generals; the bishop becomes a horse (bishop plus king) and the rook a dragon (rook plus king). Gold and king never promote. Promotion is your choice, except that a piece that could never move again must promote.
Winning. Checkmate the king. A player with no legal move loses. The same position four times over is a draw and the game is replayed — unless one side was giving check every time round, and then that side loses.
Impasse (入玉). If both kings run into the far camp and mate is off the table, a player may declare: with the king in the zone, ten pieces there or in hand, and 28 points for Black or 27 for White counting rook and bishop as 5 and everything else as 1, the declaring player wins.

The pieces

Piece	Moves	Promotes to
玉 King	One square any way	—
飛 Rook	Any distance, straight	竜 Dragon — plus one square diagonally
角 Bishop	Any distance, diagonally	馬 Horse — plus one square straight
金 Gold	One square any way but the back diagonals	—
銀 Silver	One square forward, the forward diagonals, and the back diagonals	全 as a gold
桂 Knight	Two forward and one to the side — the only jump, and it never goes back	圭 as a gold
香 Lance	Any distance straight forward, never back	杏 as a gold
歩 Pawn	One square forward	と Tokin — as a gold

What the pieces are worth

Three groups. The king has no price at all — lose it and the game is over. The two major pieces (大駒) are the rook and the bishop. Everything else is a minor piece (小駒): gold, silver, knight, lance and pawn.
Among the minors the order is gold > silver > (knight, lance) > pawn. Gold and silver are close: the gold defends its sides better, the silver attacks better because it can retreat. Knight and lance are close too — neither can ever turn round.
None of this is standardised. Strong players disagree about the exact numbers, and every shogi program picks its own. The table below is what this computer uses, on the scale Grimbergen sets out — pawn 1, lance and knight 3, silver and gold 5, bishop 8, rook 9 — with the ties inside each group split the way the hierarchy orders them.
Turning a piece over is worth about four pawns for either major piece: a bishop at 8 becomes a horse at 12, a rook at 9 becomes a dragon at 13. A pawn that reaches a tokin is worth five times what it was.
A piece in hand is worth more than the same piece on the board, because it can be dropped anywhere — and a pawn in hand most of all, since it is the raw material for a tokin.

Piece	On the board	In hand
歩 Pawn	1	1.2
香 Lance	3	3.3
桂 Knight	3.2	3.6
銀 Silver	5	5.4
金 Gold	5.4	5.9
角 Bishop	8	8.8
飛 Rook	9	9.8
と Tokin, and every promoted minor	5.4	as the piece it was
馬 Horse (promoted bishop)	12	—
竜 Dragon (promoted rook)	13	—

The opening

Build the castle first. Shogi openings are slower than chess: a quick attack leaves your own camp open to drops the moment pieces are exchanged. Expect a dozen moves of preparation before anyone comes forward.
Three generals round the king — two golds and a silver — is the shape every castle aims for. A king left on its starting square (igyoku, "sitting king") is asking to be mated.
Keep the king away from your own rook. Static Rook openings leave the rook at home on the right and castle to the left (Boat, Yagura, Bear-in-the-hole). Ranging Rook openings swing the rook to the centre or left and castle to the right (Mino), inviting the attack and aiming for the counter.
Rook pawn or bishop pawn. P-2f opens for the rook; P-7f opens the bishop's diagonal. After a bishop opening the bishops are often traded — but a trade costs a tempo and hands your opponent a piece to drop into your camp, so it wants a reason.
Silvers attack, golds defend. A silver can retreat; a gold guards its sides better. Advance a silver with pawns behind it, and leave the golds at home.

The middlegame

Pieces in hand are the game. Players will exchange, or even sacrifice, to get the right piece in hand — a piece in hand can appear anywhere, which is worth more than the same piece stuck on the board.
Pawns are ammunition. They attack head on and cannot defend each other, so they go early. A pawn dropped behind the lines and promoted to a tokin, with a second pawn dropped behind it so the two protect each other, threatens a whole defence and costs you almost nothing if it fails.
A dropped pawn cuts off a retreat. That is why the rook — which retreats in only one direction — is kept at a safe distance early and used to support an attack by lesser pieces. Once the position opens up, a promoted rook behind enemy lines is the strongest piece on the board.

The endgame

It starts when a defence collapses. Once someone is through, the defending king is often trapped by its own pieces — the last-ditch answer is to open the pawn line and run, because a king in the open is much harder to mate, especially against an opponent short of rooks, bishops and lances.
Then it is a race. Count the moves to mate for both sides as if the other player never moved — speed counting — and let the difference decide whether to attack or to spend a move defending. One tempo settles most endgames.
Practise tsume. Mating problems where every move is check are how strong players train the endgame, and they are the same thing this computer does before every move.

How the computer plays

It looks for mate first. Before anything else it searches through checking moves only — the same counting a player does in an endgame race. If there is a forced mate it plays it, and says so.
Then it searches with alpha-beta, iterative deepening, a transposition table, killer and history move ordering, check extensions and a quiescence search over captures, so it is never fooled by half of an exchange. Medium looks about a second deep, Hard nearly three.
It counts material the way a player does — the table under "What the pieces are worth" is its own — and adds to it what a piece in hand is worth, which is more than the same piece on the board.
Its judgement changes with the phase. In the opening it scores castles as shapes — Mino, Yagura, Boat, Bear-in-the-hole — and walks its pieces into one, keeping the king away from its own rook and off its starting square. In the middlegame it values pieces in hand above pieces on the board, rewards tokin that protect each other, and knows a rook deep in enemy territory with nowhere to run is nearly lost. In the endgame king safety outweighs material, and a king in the open is scored as hard to mate.
Levels. Easy sees the good moves but does not always choose them. Medium plays soundly. Hard searches deepest and looks five plies of check ahead for mate.