X-Git-Url: https://git.auder.net/?a=blobdiff_plain;f=client%2Fsrc%2Fvariants%2FMaxima.js;fp=client%2Fsrc%2Fvariants%2FMaxima.js;h=ab97a2177308fa7f4cb9ede94267c38bd4803816;hb=e90bafa8fb5fb7641728231bf2398590d96c672a;hp=0000000000000000000000000000000000000000;hpb=2f8dce6a81063289d9d4cbca7971f80b1b194b84;p=vchess.git

diff --git a/client/src/variants/Maxima.js b/client/src/variants/Maxima.js
new file mode 100644
index 00000000..ab97a217
--- /dev/null
+++ b/client/src/variants/Maxima.js
@@ -0,0 +1,832 @@
+import { ChessRules, PiPo, Move } from "@/base_rules";
+import { ArrayFun } from "@/utils/array";
+import { shuffle } from "@/utils/alea";
+
+export class MaximaRules extends ChessRules {
+  static get HasFlags() {
+    return false;
+  }
+
+  static get HasEnpassant() {
+    return false;
+  }
+
+  static get PIECES() {
+    return ChessRules.PIECES.concat([V.IMMOBILIZER, V.MAGE, V.GUARD]);
+  }
+
+  getPpath(b) {
+    if (b[0] == 'x') return "Maxima/nothing";
+    if (['m','d','g'].includes(b[1]))
+      return "Maxima/" + b;
+    return b;
+  }
+
+  // For space next to the palaces:
+  static get NOTHING() {
+    return "xx";
+  }
+
+  static board2fen(b) {
+    if (b[0] == 'x') return 'x';
+    return ChessRules.board2fen(b);
+  }
+
+  static fen2board(f) {
+    if (f == 'x') return V.NOTHING;
+    return ChessRules.fen2board(f);
+  }
+
+  // TODO: the wall position should be checked too
+  static IsGoodPosition(position) {
+    if (position.length == 0) return false;
+    const rows = position.split("/");
+    if (rows.length != V.size.x) return false;
+    let kings = { "k": 0, "K": 0 };
+    for (let row of rows) {
+      let sumElts = 0;
+      for (let i = 0; i < row.length; i++) {
+        if (['K','k'].includes(row[i])) kings[row[i]]++;
+        if (['x'].concat(V.PIECES).includes(row[i].toLowerCase())) sumElts++;
+        else {
+          const num = parseInt(row[i]);
+          if (isNaN(num)) return false;
+          sumElts += num;
+        }
+      }
+      if (sumElts != V.size.y) return false;
+    }
+    if (Object.values(kings).some(v => v != 1)) return false;
+    return true;
+  }
+
+  // No castling, but checks, so keep track of kings
+  setOtherVariables(fen) {
+    this.kingPos = { w: [-1, -1], b: [-1, -1] };
+    const fenParts = fen.split(" ");
+    const position = fenParts[0].split("/");
+    for (let i = 0; i < position.length; i++) {
+      let k = 0;
+      for (let j = 0; j < position[i].length; j++) {
+        switch (position[i].charAt(j)) {
+          case "k":
+            this.kingPos["b"] = [i, k];
+            break;
+          case "K":
+            this.kingPos["w"] = [i, k];
+            break;
+          default: {
+            const num = parseInt(position[i].charAt(j));
+            if (!isNaN(num)) k += num - 1;
+          }
+        }
+        k++;
+      }
+    }
+  }
+
+  static get size() {
+    return { x: 11, y: 8 };
+  }
+
+  static OnBoard(x, y) {
+    return (
+      (x >= 1 && x <= 9 && y >= 0 && y <= 7) ||
+      ([3, 4].includes(y) && [0, 10].includes(x))
+    );
+  }
+
+  static get IMMOBILIZER() {
+    return "m";
+  }
+  static get MAGE() {
+    return 'g';
+  }
+  static get GUARD() {
+    return 'd';
+  }
+  // Although other pieces keep their names here for coding simplicity,
+  // keep in mind that:
+  //  - a "rook" is a coordinator, capturing by coordinating with the king
+  //  - a "knight" is a long-leaper, capturing as in draughts
+  //  - a "bishop" is a chameleon, capturing as its prey
+  //  - a "queen" is a withdrawer, capturing by moving away from pieces
+
+  // Is piece on square (x,y) immobilized?
+  isImmobilized([x, y]) {
+    const piece = this.getPiece(x, y);
+    if (piece == V.MAGE)
+      // Mages are not immobilized:
+      return false;
+    const oppCol = V.GetOppCol(this.getColor(x, y));
+    const adjacentSteps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
+    for (let step of adjacentSteps) {
+      const [i, j] = [x + step[0], y + step[1]];
+      if (
+        V.OnBoard(i, j) &&
+        this.board[i][j] != V.EMPTY &&
+        this.getColor(i, j) == oppCol
+      ) {
+        const oppPiece = this.getPiece(i, j);
+        if (oppPiece == V.IMMOBILIZER) return [i, j];
+        // Only immobilizers are immobilized by chameleons:
+        if (oppPiece == V.BISHOP && piece == V.IMMOBILIZER) return [i, j];
+      }
+    }
+    return null;
+  }
+
+  getPotentialMovesFrom([x, y]) {
+    // Pre-check: is thing on this square immobilized?
+    const imSq = this.isImmobilized([x, y]);
+    const piece = this.getPiece(x, y);
+    if (!!imSq && piece != V.KING) {
+      // Only option is suicide, if I'm not a king:
+      return [
+        new Move({
+          start: { x: x, y: y },
+          end: { x: imSq[0], y: imSq[1] },
+          appear: [],
+          vanish: [
+            new PiPo({
+              x: x,
+              y: y,
+              c: this.getColor(x, y),
+              p: this.getPiece(x, y)
+            })
+          ]
+        })
+      ];
+    }
+    let moves = undefined;
+    switch (piece) {
+      case V.IMMOBILIZER:
+        moves = this.getPotentialImmobilizerMoves([x, y]);
+        break;
+      case V.GUARD:
+        moves = this.getPotentialGuardMoves([x, y]);
+        break;
+      case V.MAGE:
+        moves = this.getPotentialMageMoves([x, y]);
+        break;
+      default:
+        moves = super.getPotentialMovesFrom([x, y]);
+    }
+    const pX = (this.turn == 'w' ? 10 : 0);
+    if (this.board[pX][3] == V.EMPTY && this.board[pX][4] == V.EMPTY)
+      return moves;
+    // Filter out moves resulting in self palace occupation:
+    // NOTE: cannot invade own palace but still check the king there.
+    const pY = (this.board[pX][3] == V.EMPTY ? 4 : 3);
+    return moves.filter(m => m.end.x != pX || m.end.y != pY);
+  }
+
+  getSlideNJumpMoves([x, y], steps, oneStep, mageInitSquare, onlyTake) {
+    const piece = !mageInitSquare ? this.getPiece(x, y) : V.MAGE;
+    const initSquare = mageInitSquare || [x, y];
+    let moves = [];
+    outerLoop: for (let step of steps) {
+      let i = x + step[0];
+      let j = y + step[1];
+      if (piece == V.KING) j = j % V.size.y;
+      while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
+        if (!onlyTake) moves.push(this.getBasicMove(initSquare, [i, j]));
+        if (!!oneStep) continue outerLoop;
+        i += step[0];
+        j += step[1];
+      }
+      // Only king, guard and mage + chameleon can take on occupied square:
+      if (
+        V.OnBoard(i, j)
+        &&
+        this.canTake(initSquare, [i, j])
+        &&
+        (
+          [V.KING, V.GUARD, V.MAGE].includes(piece) ||
+          (piece == V.BISHOP && this.getPiece(i, j) === onlyTake)
+        )
+      ) {
+        moves.push(this.getBasicMove(initSquare, [i, j]));
+      }
+    }
+    return moves;
+  }
+
+  // Modify capturing moves among listed pawn moves
+  addPawnCaptures(moves, byChameleon) {
+    const steps = V.steps[V.ROOK];
+    const color = this.turn;
+    const oppCol = V.GetOppCol(color);
+    moves.forEach(m => {
+      if (!!byChameleon && m.start.x != m.end.x && m.start.y != m.end.y)
+        // Chameleon not moving as pawn
+        return;
+      // Try capturing in every direction
+      for (let step of steps) {
+        const sq2 = [m.end.x + 2 * step[0], m.end.y + 2 * step[1]];
+        if (
+          V.OnBoard(sq2[0], sq2[1]) &&
+          this.board[sq2[0]][sq2[1]] != V.EMPTY &&
+          this.getColor(sq2[0], sq2[1]) == color
+        ) {
+          // Potential capture
+          const sq1 = [m.end.x + step[0], m.end.y + step[1]];
+          if (
+            this.board[sq1[0]][sq1[1]] != V.EMPTY &&
+            this.getColor(sq1[0], sq1[1]) == oppCol
+          ) {
+            const piece1 = this.getPiece(sq1[0], sq1[1]);
+            if (!byChameleon || piece1 == V.PAWN) {
+              m.vanish.push(
+                new PiPo({
+                  x: sq1[0],
+                  y: sq1[1],
+                  c: oppCol,
+                  p: piece1
+                })
+              );
+            }
+          }
+        }
+      }
+    });
+  }
+
+  // "Pincer"
+  getPotentialPawnMoves([x, y]) {
+    let moves = super.getPotentialRookMoves([x, y]);
+    this.addPawnCaptures(moves);
+    return moves;
+  }
+
+  addRookCaptures(moves, byChameleon) {
+    const color = this.turn;
+    const oppCol = V.GetOppCol(color);
+    const kp = this.kingPos[color];
+    moves.forEach(m => {
+      // Check piece-king rectangle (if any) corners for enemy pieces
+      if (m.end.x == kp[0] || m.end.y == kp[1]) return; //"flat rectangle"
+      const corner1 = [m.end.x, kp[1]];
+      const corner2 = [kp[0], m.end.y];
+      for (let [i, j] of [corner1, corner2]) {
+        if (this.board[i][j] != V.EMPTY && this.getColor(i, j) == oppCol) {
+          const piece = this.getPiece(i, j);
+          if (!byChameleon || piece == V.ROOK) {
+            m.vanish.push(
+              new PiPo({
+                x: i,
+                y: j,
+                p: piece,
+                c: oppCol
+              })
+            );
+          }
+        }
+      }
+    });
+  }
+
+  // Coordinator
+  getPotentialRookMoves(sq) {
+    let moves = super.getPotentialQueenMoves(sq);
+    this.addRookCaptures(moves);
+    return moves;
+  }
+
+  getKnightCaptures(startSquare, byChameleon) {
+    // Look in every direction for captures
+    const steps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
+    const color = this.turn;
+    const oppCol = V.GetOppCol(color);
+    let moves = [];
+    const [x, y] = [startSquare[0], startSquare[1]];
+    const piece = this.getPiece(x, y); //might be a chameleon!
+    outerLoop: for (let step of steps) {
+      let [i, j] = [x + step[0], y + step[1]];
+      while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
+        i += step[0];
+        j += step[1];
+      }
+      if (
+        !V.OnBoard(i, j) ||
+        this.getColor(i, j) == color ||
+        (!!byChameleon && this.getPiece(i, j) != V.KNIGHT)
+      ) {
+        continue;
+      }
+      // last(thing), cur(thing) : stop if "cur" is our color,
+      // or beyond board limits, or if "last" isn't empty and cur neither.
+      // Otherwise, if cur is empty then add move until cur square;
+      // if cur is occupied then stop if !!byChameleon and the square not
+      // occupied by a leaper.
+      let last = [i, j];
+      let cur = [i + step[0], j + step[1]];
+      let vanished = [new PiPo({ x: x, y: y, c: color, p: piece })];
+      while (V.OnBoard(cur[0], cur[1])) {
+        if (this.board[last[0]][last[1]] != V.EMPTY) {
+          const oppPiece = this.getPiece(last[0], last[1]);
+          if (!!byChameleon && oppPiece != V.KNIGHT) continue outerLoop;
+          // Something to eat:
+          vanished.push(
+            new PiPo({ x: last[0], y: last[1], c: oppCol, p: oppPiece })
+          );
+        }
+        if (this.board[cur[0]][cur[1]] != V.EMPTY) {
+          if (
+            this.getColor(cur[0], cur[1]) == color ||
+            this.board[last[0]][last[1]] != V.EMPTY
+          ) {
+            //TODO: redundant test
+            continue outerLoop;
+          }
+        } else {
+          moves.push(
+            new Move({
+              appear: [new PiPo({ x: cur[0], y: cur[1], c: color, p: piece })],
+              vanish: JSON.parse(JSON.stringify(vanished)), //TODO: required?
+              start: { x: x, y: y },
+              end: { x: cur[0], y: cur[1] }
+            })
+          );
+        }
+        last = [last[0] + step[0], last[1] + step[1]];
+        cur = [cur[0] + step[0], cur[1] + step[1]];
+      }
+    }
+    return moves;
+  }
+
+  // Long-leaper
+  getPotentialKnightMoves(sq) {
+    return super.getPotentialQueenMoves(sq).concat(this.getKnightCaptures(sq));
+  }
+
+  // Chameleon
+  getPotentialBishopMoves([x, y]) {
+    let moves = super
+      .getPotentialQueenMoves([x, y])
+      .concat(this.getKnightCaptures([x, y], "asChameleon"))
+      .concat(this.getPotentialGuardMoves([x, y], "asChameleon"))
+      .concat(this.getPotentialMageMoves([x, y], "asChameleon"));
+    // No "king capture" because king cannot remain under check
+    this.addPawnCaptures(moves, "asChameleon");
+    this.addRookCaptures(moves, "asChameleon");
+    this.addQueenCaptures(moves, "asChameleon");
+    // Post-processing: merge similar moves, concatenating vanish arrays
+    let mergedMoves = {};
+    moves.forEach(m => {
+      const key = m.end.x + V.size.x * m.end.y;
+      if (!mergedMoves[key]) mergedMoves[key] = m;
+      else {
+        for (let i = 1; i < m.vanish.length; i++)
+          mergedMoves[key].vanish.push(m.vanish[i]);
+      }
+    });
+    return Object.values(mergedMoves);
+  }
+
+  addQueenCaptures(moves, byChameleon) {
+    if (moves.length == 0) return;
+    const [x, y] = [moves[0].start.x, moves[0].start.y];
+    const adjacentSteps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
+    let capturingDirections = [];
+    const color = this.turn;
+    const oppCol = V.GetOppCol(color);
+    adjacentSteps.forEach(step => {
+      const [i, j] = [x + step[0], y + step[1]];
+      if (
+        V.OnBoard(i, j) &&
+        this.board[i][j] != V.EMPTY &&
+        this.getColor(i, j) == oppCol &&
+        (!byChameleon || this.getPiece(i, j) == V.QUEEN)
+      ) {
+        capturingDirections.push(step);
+      }
+    });
+    moves.forEach(m => {
+      const step = [
+        m.end.x != x ? (m.end.x - x) / Math.abs(m.end.x - x) : 0,
+        m.end.y != y ? (m.end.y - y) / Math.abs(m.end.y - y) : 0
+      ];
+      // TODO: this test should be done only once per direction
+      if (
+        capturingDirections.some(dir => {
+          return dir[0] == -step[0] && dir[1] == -step[1];
+        })
+      ) {
+        const [i, j] = [x - step[0], y - step[1]];
+        m.vanish.push(
+          new PiPo({
+            x: i,
+            y: j,
+            p: this.getPiece(i, j),
+            c: oppCol
+          })
+        );
+      }
+    });
+  }
+
+  // Withdrawer
+  getPotentialQueenMoves(sq) {
+    let moves = super.getPotentialQueenMoves(sq);
+    this.addQueenCaptures(moves);
+    return moves;
+  }
+
+  getPotentialImmobilizerMoves(sq) {
+    // Immobilizer doesn't capture
+    return super.getPotentialQueenMoves(sq);
+  }
+
+  getPotentialKingMoves(sq) {
+    return this.getSlideNJumpMoves(sq, V.steps[V.KNIGHT], "oneStep");
+  }
+
+  getPotentialGuardMoves(sq, byChameleon) {
+    const onlyTake = !byChameleon ? null : V.GUARD;
+    return (
+      this.getSlideNJumpMoves(
+        sq,
+        V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
+        "oneStep",
+        null,
+        onlyTake
+      )
+    );
+  }
+
+  getNextMageSteps(step) {
+    if (step[0] == -1) {
+      if (step[1] == -1) return [[-1, 0], [0, -1]];
+      return [[-1, 0], [0, 1]];
+    }
+    if (step[1] == -1) return [[1, 0], [0, -1]];
+    return [[1, 0], [0, 1]];
+  }
+
+  getPotentialMageMoves([x, y], byChameleon) {
+    const oppCol = V.GetOppCol(this.turn);
+    const onlyTake = !byChameleon ? null : V.MAGE;
+    let moves = [];
+    for (let step of V.steps[V.BISHOP]) {
+      let [i, j] = [x + step[0], y + step[1]];
+      if (!V.OnBoard(i, j)) continue;
+      if (this.board[i][j] != V.EMPTY) {
+        if (
+          this.getColor(i, j) == oppCol &&
+          (!onlyTake || this.getPiece(i, j) == V.MAGE)
+        ) {
+          // Capture
+          moves.push(this.getBasicMove([x, y], [i, j]));
+        }
+      }
+      else {
+        if (!onlyTake) moves.push(this.getBasicMove([x, y], [i, j]));
+        // Continue orthogonally:
+        const stepO = this.getNextMageSteps(step);
+        Array.prototype.push.apply(
+          moves,
+          this.getSlideNJumpMoves([i, j], stepO, null, [x, y], onlyTake)
+        );
+      }
+    }
+    return moves;
+  }
+
+  isAttacked(sq, color) {
+    return (
+      super.isAttacked(sq, color) ||
+      this.isAttackedByGuard(sq, color) ||
+      this.isAttackedByMage(sq, color)
+    );
+  }
+
+  isAttackedByPawn([x, y], color) {
+    // Square (x,y) must be surroundable by two enemy pieces,
+    // and one of them at least should be a pawn (moving).
+    const dirs = [
+      [1, 0],
+      [0, 1]
+    ];
+    const steps = V.steps[V.ROOK];
+    for (let dir of dirs) {
+      const [i1, j1] = [x - dir[0], y - dir[1]]; //"before"
+      const [i2, j2] = [x + dir[0], y + dir[1]]; //"after"
+      if (V.OnBoard(i1, j1) && V.OnBoard(i2, j2)) {
+        if (
+          (
+            this.board[i1][j1] != V.EMPTY &&
+            this.getColor(i1, j1) == color &&
+            this.board[i2][j2] == V.EMPTY
+          )
+          ||
+          (
+            this.board[i2][j2] != V.EMPTY &&
+            this.getColor(i2, j2) == color &&
+            this.board[i1][j1] == V.EMPTY
+          )
+        ) {
+          // Search a movable enemy pawn landing on the empty square
+          for (let step of steps) {
+            let [ii, jj] = this.board[i1][j1] == V.EMPTY ? [i1, j1] : [i2, j2];
+            let [i3, j3] = [ii + step[0], jj + step[1]];
+            while (V.OnBoard(i3, j3) && this.board[i3][j3] == V.EMPTY) {
+              i3 += step[0];
+              j3 += step[1];
+            }
+            if (
+              V.OnBoard(i3, j3) &&
+              this.getColor(i3, j3) == color &&
+              this.getPiece(i3, j3) == V.PAWN &&
+              !this.isImmobilized([i3, j3])
+            ) {
+              return true;
+            }
+          }
+        }
+      }
+    }
+    return false;
+  }
+
+  isAttackedByRook([x, y], color) {
+    // King must be on same column or row,
+    // and a rook should be able to reach a capturing square
+    const sameRow = x == this.kingPos[color][0];
+    const sameColumn = y == this.kingPos[color][1];
+    if (sameRow || sameColumn) {
+      // Look for the enemy rook (maximum 1)
+      for (let i = 0; i < V.size.x; i++) {
+        for (let j = 0; j < V.size.y; j++) {
+          if (
+            this.board[i][j] != V.EMPTY &&
+            this.getColor(i, j) == color &&
+            this.getPiece(i, j) == V.ROOK
+          ) {
+            if (this.isImmobilized([i, j]))
+              // Because only one rook:
+              return false;
+            // Can it reach a capturing square? Easy but quite suboptimal way
+            // (TODO: generate all moves (turn is OK))
+            const moves = this.getPotentialMovesFrom([i, j]);
+            for (let move of moves) {
+              if (
+                (sameRow && move.end.y == y) ||
+                (sameColumn && move.end.x == x)
+              ) {
+                return true;
+              }
+            }
+          }
+        }
+      }
+    }
+    return false;
+  }
+
+  isAttackedByKnight([x, y], color) {
+    // Square (x,y) must be on same line as a knight,
+    // and there must be empty square(s) behind.
+    const steps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
+    outerLoop: for (let step of steps) {
+      const [i0, j0] = [x + step[0], y + step[1]];
+      if (V.OnBoard(i0, j0) && this.board[i0][j0] == V.EMPTY) {
+        // Try in opposite direction:
+        let [i, j] = [x - step[0], y - step[1]];
+        while (V.OnBoard(i, j)) {
+          while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
+            i -= step[0];
+            j -= step[1];
+          }
+          if (V.OnBoard(i, j)) {
+            if (this.getColor(i, j) == color) {
+              if (
+                this.getPiece(i, j) == V.KNIGHT &&
+                !this.isImmobilized([i, j])
+              ) {
+                return true;
+              }
+              continue outerLoop;
+            }
+            // [else] Our color,
+            // could be captured *if there was an empty space*
+            if (this.board[i + step[0]][j + step[1]] != V.EMPTY)
+              continue outerLoop;
+            i -= step[0];
+            j -= step[1];
+          }
+        }
+      }
+    }
+    return false;
+  }
+
+  isAttackedByBishop([x, y], color) {
+    // We cheat a little here: since this function is used exclusively for
+    // the king, it's enough to check the immediate surrounding of the square.
+    const adjacentSteps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
+    for (let step of adjacentSteps) {
+      const [i, j] = [x + step[0], y + step[1]];
+      if (
+        V.OnBoard(i, j) &&
+        this.board[i][j] != V.EMPTY &&
+        this.getColor(i, j) == color &&
+        this.getPiece(i, j) == V.BISHOP &&
+        !this.isImmobilized([i, j])
+      ) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  isAttackedByQueen([x, y], color) {
+    // Square (x,y) must be adjacent to a queen, and the queen must have
+    // some free space in the opposite direction from (x,y)
+    const adjacentSteps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
+    for (let step of adjacentSteps) {
+      const sq2 = [x + 2 * step[0], y + 2 * step[1]];
+      if (V.OnBoard(sq2[0], sq2[1]) && this.board[sq2[0]][sq2[1]] == V.EMPTY) {
+        const sq1 = [x + step[0], y + step[1]];
+        if (
+          this.board[sq1[0]][sq1[1]] != V.EMPTY &&
+          this.getColor(sq1[0], sq1[1]) == color &&
+          this.getPiece(sq1[0], sq1[1]) == V.QUEEN &&
+          !this.isImmobilized(sq1)
+        ) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  isAttackedByKing([x, y], color) {
+    for (let step of V.steps[V.KNIGHT]) {
+      let rx = x + step[0],
+          // Circular board for king-knight:
+          ry = (y + step[1]) % V.size.y;
+      if (
+        V.OnBoard(rx, ry) &&
+        this.getPiece(rx, ry) === V.KING &&
+        this.getColor(rx, ry) == color &&
+        !this.isImmobilized([rx, ry])
+      ) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  isAttackedByGuard(sq, color) {
+    return (
+      super.isAttackedBySlideNJump(
+        sq,
+        color,
+        V.GUARD,
+        V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
+        "oneStep"
+      )
+    );
+  }
+
+  getNextMageCheck(step) {
+    if (step[0] == 0) {
+      if (step[1] == 1) return [[1, 1], [-1, 1]];
+      return [[-1, -1], [1, -1]];
+    }
+    if (step[0] == -1) return [[-1, -1], [-1, 1]];
+    return [[1, 1], [1, -1]];
+  }
+
+  isAttackedByMage([x, y], color) {
+    for (let step of V.steps[V.BISHOP]) {
+      const [i, j] = [x + step[0], y + step[1]];
+      if (
+        V.OnBoard(i, j) &&
+        this.board[i][j] != V.EMPTY &&
+        this.getColor(i, j) == color &&
+        this.getPiece(i, j) == V.MAGE
+      ) {
+        return true;
+      }
+    }
+    for (let step of V.steps[V.ROOK]) {
+      let [i, j] = [x + step[0], y + step[1]];
+      const stepM = this.getNextMageCheck(step);
+      while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
+        for (let s of stepM) {
+          const [ii, jj] = [i + s[0], j + s[1]];
+          if (
+            V.OnBoard(ii, jj) &&
+            this.board[ii][jj] != V.EMPTY &&
+            this.getColor(ii, jj) == color &&
+            this.getPiece(ii, jj) == V.MAGE
+          ) {
+            return true;
+          }
+        }
+        i += step[0];
+        j += step[1];
+      }
+    }
+    return false;
+  }
+
+  getCurrentScore() {
+    const color = this.turn;
+    const getScoreLost = () => {
+      // Result if I lose:
+      return color == "w" ? "0-1" : "1-0";
+    };
+    if (!this.atLeastOneMove()) {
+      // No valid move: I lose or draw
+      if (this.underCheck(color)) return getScoreLost();
+      return "1/2";
+    }
+    // I lose also if no pieces left (except king)
+    let piecesLeft = 0;
+    outerLoop: for (let i=0; i<V.size.x; i++) {
+      for (let j=0; j<V.size.y; j++) {
+        if (
+          this.board[i][j] != V.EMPTY &&
+          this.getColor(i, j) == color &&
+          this.getPiece(i,j) != V.KING
+        ) {
+          piecesLeft++;
+        }
+      }
+    }
+    if (piecesLeft == 0) return getScoreLost();
+    // Check if my palace is invaded:
+    const pX = (color == 'w' ? 10 : 0);
+    const oppCol = V.GetOppCol(color);
+    if (
+      this.board[pX][3] != V.EMPTY &&
+      this.getColor(pX, 3) == oppCol &&
+      this.board[pX][4] != V.EMPTY &&
+      this.getColor(pX, 4) == oppCol
+    ) {
+      return getScoreLost();
+    }
+    return "*";
+  }
+
+  static GenRandInitFen() {
+    // Always deterministic:
+    return (
+      "xxx2xxx/1g1qk1g1/1bnmrnb1/dppppppd/8/8/8/" +
+      "DPPPPPPD/1BNMRNB1/1G1QK1G1/xxx2xxx w 0"
+    );
+  }
+
+  static get VALUES() {
+    return {
+      p: 1,
+      r: 2,
+      n: 5,
+      b: 4,
+      q: 2,
+      m: 5,
+      g: 7,
+      d: 4,
+      k: 1000
+    };
+  }
+
+  static get SEARCH_DEPTH() {
+    return 2;
+  }
+
+  evalPosition() {
+    let evaluation = 0;
+    for (let i = 0; i < V.size.x; i++) {
+      for (let j = 0; j < V.size.y; j++) {
+        if (![V.EMPTY,V.NOTHING].includes(this.board[i][j])) {
+          const sign = this.getColor(i, j) == "w" ? 1 : -1;
+          evaluation += sign * V.VALUES[this.getPiece(i, j)];
+        }
+      }
+    }
+    return evaluation;
+  }
+
+  getNotation(move) {
+    const initialSquare = V.CoordsToSquare(move.start);
+    const finalSquare = V.CoordsToSquare(move.end);
+    if (move.appear.length == 0)
+      // Suicide 'S'
+      return initialSquare + "S";
+    let notation = undefined;
+    if (move.appear[0].p == V.PAWN) {
+      // Pawn: generally ambiguous short notation, so we use full description
+      notation = "P" + initialSquare + finalSquare;
+    } else if (move.appear[0].p == V.KING)
+      notation = "K" + (move.vanish.length > 1 ? "x" : "") + finalSquare;
+    else notation = move.appear[0].p.toUpperCase() + finalSquare;
+    // Add a capture mark (not describing what is captured...):
+    if (move.vanish.length > 1 && move.appear[0].p != V.KING) notation += "X";
+    return notation;
+  }
+};