Cashew Shogi

Cashew Shogi is inspired by the historic Japanese Chess variant Dai Dai Shogi. The latter game contains many unique and interesting ideas (e.g. multiple captures, hook movers, promotion by capture). But it is huge (17x17 board, 96 pieces of 64 types, with 4 more types available through promotion), so that it is quite tedious to play. Cashew Shogi is Dai Dai Shogi shrunk by roughly a factor two, by selecting a subset of the pieces (54 pieces of 35 types, with 2 more available through promotion) on a 13x13 board. This is done to conserve the feel of the game as much as possible, by selecting the key pieces, and a representative set of the others, with a slight bias against the very weakest of each class.

Setup

Click on piece name to see how it moves

• g1, g13 King (K)
• f1, h13 Left General (FvrW)
• h1, g13 Right General (FvlW)
• e1, i13 Queen (Q)
• i1, e13 Flying Horse (WfF2) promotes to Queen
• c1, k13 Crowned Bishop (BW)
• d1, j13 Butterfly (F) promotes to Crowned Bishop
• j1, d13 Castle (RF)
• k1, c13 Dragon (F2) promotes to Castle
• b1, l13 Goblin (BW(B-sB))
• b2, l12 Kite (W2fF) promotes to Goblin
• l1, b13 Hook Mover (R(R-sR))
• l2, b12 Viper (sWfDbA) promotes to Hook Mover
• a1, m1, a13, m13 Lance (fR)

• f2, h2, g12, h12: Gold (WfF)
• j2, d12 Unicorn (sRvW2F3)
• i1, e12 Kirin (FD) promotes to Unicorn
• c2, k12 Lion (KNAD(cK-aK)(mK-bK), see below) promotes to Berserker
• c3, k11 Viking (sW2vWfF) promotes to Wolf
• d2, j12 Golden Bird (vRsW2F3)
• e2, i12 Phoenix (WA) promotes to Golden Bird
• k2, c12 Wolf (KADHG(...), see below) promotes to Elephant
• c11, k3 Hun (fW2sWfF) promotes to Lion
• a2, m12 Broad Guard (sRvW2rfBlfF)
• m2, a12 Deep Guard (vRsW2lfBrF)

• g3, g11 Flag (fRfBbsW2bF2)
• g2, g12: Commoner (K) promotes to Flag
• f3, h11, h3, f11 Tiger (vW2fF)
• e3, i11, i3, e11 Silver (FfW)
• d3, j3, d11, j11 Leopard (FvW)
• b3, l3, b11, l11 Bear (sWfF2)
• a3, m11 Left Chariot (fRbWlfrbB)
• m3, a11 Right Chariot (fRbWrflbB)

• Berserker (Lion + K3)
• Elephant (vW3sW5fF3bF5)

Pieces

Hook movers

The Hook Mover is a Rook that can (but doesn't have to) make one 90-degree turn in its trajectory. On an empty board it could reach any square, most of them in two ways. A Goblin is a Bishop that can do likewise. Which means it can reach any square of its color on an empty board. It furthermore can step one orthogonally to reach the other color.

Wolf

The Wolf is a triple mover: it can move make upto 3 King steps along a ray, and even return to its starting square (but not overshoot it). It can make these steps as jumps when it choses to do so. So it can:

• Jump directly to any square 1-3 steps away along Queen rays, irrespective of what other squares are occupied,
• Annihilate any opponent standing next to it, without moving (formally one step, and then a step back),
• Step one square in any direction, annihilating what was 2 steps away in that direction (formally 2 steps out, 1 in)
• Jump to the second square in any direction, annihilating the opponent it jumped over,
• Move to the third square in any direction, annihilating the opponent on the first square it jumped over, irrespective of what is on the second square,
• Move to the third square in any direction, annihilating the opponent on the second square it jumped over, irrespective of what is on the first square,
• Move to the third square in any direction, annihilating the opponents on both the first and the second square it jumped over.
• Stay in place without capturing anything if one of the neighboring squares is empty (effectively passing a turn).

Lion, Berserker

A Berserker moves as a Lion or slides upto 3 squares in any of the 8 directions. The Lion is a double mover: it can make upto 2 King steps per turn, changing direction between them, even when this returns it to its starting square. It can make the first step as jump, when it chooses to do so. So it can:

• Jump directly to any square in the 5x5 area surrounding it,
• Annihilate any opponent standing next to it, without moving (formally one step, and then a step back),
• Annihilate any opponent standing next to it, moving on to an empty square next to that ('hit and run'),
• Annihilate any opponent standing next to it, and normally capture an opponent standing next to that ('double capture'),
• Stay in place without capturing anything if one of the neighboring squares is empty (effectively passing a turn).

Rules

Goal

The game is won by capturing the opponent's King.

Promotion

Many pieces besides Pawns can promote. There is no choice for what they promote to; each piece has a fixed promoted form, which can be different for each piece type. Promotion is irreversible, and once the piece is promoted it keeps the promoted form for the rest of the game, or until it is captured. Promotion can happen anywhere on the board, but only when the piece captures something, and is mandatory in that case (when the piece is promotable).

Repetition

Repeating a position that has occurred previously (with the same side to move) is in principle forbidden. But to prevent abuse of this rule for material gains and allowing draws in positions where really nothing can be achieved anymore, the outcome of the game is not automatically a loss for the side whose move created the repeated position, but will depend on all moves since the previous occurrence of the position as follows:

• If one side has been checking with all his moves, that side loses. (In other words: perpetual checking is always forbidden).
• If one side did not attack anything with any of his moves, but the other did, that latter side loses. (This outlaws perpetual chasing.)
• If neither side attacked anything with any of their moves, the game is drawn.

Notes

The initial setup has 10 piece types that come as a pair, and do not promote. (In the 3 cases where these are asymmetric these come as mirrored left and right versions.) Ten other piece types are promotable, and in those cases you start with both one of the promotable piece, and one of the piece it promotes to. The latter in general is not promotable, and thus could be considered as already promoted. Lion and Wolf are the only pieces that can be obtained through promotion, but occur in the initial setup not as the already promoted version of the Viking and Hun, but as promotable pieces (promoting to Berserker or Elephant).

Apart from being an interesting game in itself, Cashew Shogi can be used as a convenient first step towards learning the larger game, as the rules in no way contradict these of Dai Dai Shogi, but are a true sub-set of those.

I renamed a few pieces compared to Dai Dai Shogi, to prevent there were too many Dragons, Tigers, Elephants and such, and try to give them names that would be more easily to associate with available WinBoard piece graphics, and be slightly more mnemonic for their move. The Deep and Broad Guard were originally called 'White Tiger' and 'Blue Dragon'. The Unicorn was a Great Dragon, and what here are called Dragon and Tiger were originally 'Flying Dragon' and 'Savage Tiger'. The Butterfly was originally a 'Cat Sword', whatever that may mean. Castle and Crowned Bishop are used here for the 'Dragon King' and 'Dragon Horse' also known from regular Shogi. The Eastern and Western Barbarians became Viking and Hun. The Gun was originally a 'Howling Dog'.