Sashité for Developers
  1. Sashité for Developers
  2. Rules
  3. Chess

Chess

Rule System for Western Chess built on the Game Protocol.

1. Board

8×8 grid encoded in CELL.

Valid coordinates: a1–h8

FEEN serialization: rank 8 → rank 1, file a → file h, / between ranks.

2. Style

SNN SIN Side
Chess C first (White)
Chess c second (Black)

3. Pieces

All pieces encoded in PIN.

PIN Name Notes
+K^ King Castling rights intact
K^ King Castling rights forfeited
Q Queen  
+R Rook Castling-eligible
R Rook  
B Bishop  
N Knight  
+P Pawn Two-square advance available
P Pawn  
-P Pawn Vulnerable to en passant
+k^ King Castling rights intact
k^ King Castling rights forfeited
q Queen  
+r Rook Castling-eligible
r Rook  
b Bishop  
n Knight  
+p Pawn Two-square advance available
p Pawn  
-p Pawn Vulnerable to en passant

4. Initial Position

Encoded in FEEN:

+rnbq+k^bn+r/+p+p+p+p+p+p+p+p/8/8/8/8/+P+P+P+P+P+P+P+P/+RNBQ+K^BN+R / C/c

5. Movements

All pseudo-legal moves encoded in GGN. Patterns shown are representative; full GGN enumerates all source/destination pairs.

5.1 King

{
  "C:K^": {
    "e4": {
      "d3": [{ "must": { "d3": "empty" } }, { "must": { "d3": "enemy" } }],
      "d4": [{ "must": { "d4": "empty" } }, { "must": { "d4": "enemy" } }],
      "d5": [{ "must": { "d5": "empty" } }, { "must": { "d5": "enemy" } }],
      "e3": [{ "must": { "e3": "empty" } }, { "must": { "e3": "enemy" } }],
      "e5": [{ "must": { "e5": "empty" } }, { "must": { "e5": "enemy" } }],
      "f3": [{ "must": { "f3": "empty" } }, { "must": { "f3": "enemy" } }],
      "f4": [{ "must": { "f4": "empty" } }, { "must": { "f4": "enemy" } }],
      "f5": [{ "must": { "f5": "empty" } }, { "must": { "f5": "enemy" } }]
    }
  }
}

One square in any direction. State mutation on move: +K^ → K^, +k^ → k^.

5.2 Queen

{
  "C:Q": {
    "d1": {
      "d4": [
        { "must": { "d2": "empty", "d3": "empty", "d4": "empty" } },
        { "must": { "d2": "empty", "d3": "empty", "d4": "enemy" } }
      ],
      "a4": [
        { "must": { "c2": "empty", "b3": "empty", "a4": "empty" } },
        { "must": { "c2": "empty", "b3": "empty", "a4": "enemy" } }
      ]
    }
  }
}

Any number of squares orthogonally or diagonally. Path must be clear.

5.3 Rook

{
  "C:+R": {
    "a1": {
      "a4": [
        { "must": { "a2": "empty", "a3": "empty", "a4": "empty" } },
        { "must": { "a2": "empty", "a3": "empty", "a4": "enemy" } }
      ]
    }
  }
}

Any number of squares orthogonally. Path must be clear. State mutation on move: +R → R, +r → r.

5.4 Bishop

{
  "C:B": {
    "c1": {
      "f4": [
        { "must": { "d2": "empty", "e3": "empty", "f4": "empty" } },
        { "must": { "d2": "empty", "e3": "empty", "f4": "enemy" } }
      ]
    }
  }
}

Any number of squares diagonally. Path must be clear.

5.5 Knight

{
  "C:N": {
    "b1": {
      "a3": [{ "must": { "a3": "empty" } }, { "must": { "a3": "enemy" } }],
      "c3": [{ "must": { "c3": "empty" } }, { "must": { "c3": "enemy" } }]
    }
  }
}

L-shape (2+1 or 1+2). Jumps over pieces.

5.6 Pawn (White)

{
  "C:+P": {
    "e2": {
      "e3": [{ "must": { "e3": "empty" } }],
      "e4": [{ "must": { "e3": "empty", "e4": "empty" } }],
      "d3": [{ "must": { "d3": "enemy" } }],
      "f3": [{ "must": { "f3": "enemy" } }]
    }
  },
  "C:P": {
    "e3": {
      "e4": [{ "must": { "e4": "empty" } }],
      "d4": [{ "must": { "d4": "enemy" } }],
      "f4": [{ "must": { "f4": "enemy" } }]
    }
  }
}

5.7 Pawn (Black)

Mirror of White pawn moving toward rank 1. Reaching rank 1: mandatory promotion to q, r, b, or n.

5.8 Castling (White)

{
  "C:+K^": {
    "e1": {
      "g1": [{ "must": { "f1": "empty", "g1": "empty", "h1": "C:+R" } }],
      "c1": [{ "must": { "d1": "empty", "c1": "empty", "b1": "empty", "a1": "C:+R" } }]
    }
  }
}

State mutations: +K^ → K^, +R → R.

5.9 Castling (Black)

{
  "c:+k^": {
    "e8": {
      "g8": [{ "must": { "f8": "empty", "g8": "empty", "h8": "c:+r" } }],
      "c8": [{ "must": { "d8": "empty", "c8": "empty", "b8": "empty", "a8": "c:+r" } }]
    }
  }
}

State mutations: +k^ → k^, +r → r.

5.10 En passant

{
  "C:P": {
    "e5": {
      "d6": [{ "must": { "d5": "c:-p", "d6": "empty" } }],
      "f6": [{ "must": { "f5": "c:-p", "f6": "empty" } }]
    }
  },
  "c:p": {
    "e4": {
      "d3": [{ "must": { "d4": "C:-P", "d3": "empty" } }],
      "f3": [{ "must": { "f4": "C:-P", "f3": "empty" } }]
    }
  }
}

Captures pawn marked -P/-p (vulnerable). The -P/-p state expires at end of opponent’s turn.

6. Special Move Notation

Encoded in PMN.

Move PMN Description
Kingside castling (White) e1~g1 King e1→g1, Rook h1→f1
Queenside castling (White) e1~c1 King e1→c1, Rook a1→d1
Kingside castling (Black) e8~g8 King e8→g8, Rook h8→f8
Queenside castling (Black) e8~c8 King e8→c8, Rook a8→d8
En passant (White) e5~f6 Pawn e5→f6, captures pawn on f5
En passant (Black) e4~f3 Pawn e4→f3, captures pawn on f4
Promotion e7-e8/Q Pawn e7→e8, promotes to Queen

7. Termination

Status values from CGSN with game-specific interpretation.

7.1 Decisive

CGSN Status Result
checkmate Active player loses
resignation Resigning player loses
timelimit Player exceeding time loses (unless opponent has insufficient material → draw)

7.2 Draw

CGSN Status Condition
stalemate No legal move, not in check
insufficient K vs K, K+B vs K, K+N vs K, K+B vs K+B (same color)
repetition Same position 3 times (same active player, castling rights, en passant rights)
movelimit 50 moves without pawn move or capture
agreement Mutual agreement

8. Constraints

Rules transforming pseudo-legal moves (GGN) into legal moves.

8.1 Check constraint

A move is illegal if it leaves the active player’s King (K^/k^) in check.

8.2 Castling constraints

Castling is illegal if:

8.3 En passant timing

The -P/-p state (vulnerable to en passant) expires immediately after the opponent’s next move. En passant capture must occur on the immediately following turn.

8.4 Threefold repetition

Position identity includes:

9. Reference

10. License

Open Web Foundation Agreement 1.0 (OWFa 1.0) — OWFa 1.0