--- /dev/null
+p.boxed
+ | Both players play a move "at the same time".
+ | The goal is to eliminate all pawns.
+
+p
+ | This variant is inspired by the
+ a(href="https://en.wikipedia.org/wiki/Four_Horsemen_of_the_Apocalypse")
+ | Four Horsemen of the Apocalypse
+ | mythology. Knights are horsemen, and pawns are footmen.
+ | The goal is to eliminate all enemy footmen,
+ | most likely with the help of your horsemen.
+ | If all footmen die, the other side wins.
+
+p.
+ At each turn you can decide either to play safely an apparently valid move,
+ or speculate on your opponent's move and choose a move valid only
+ conditionally on his choice. In this last case the move may end up not
+ being playable: you would get a penalty point. Two penalty points loses
+ the game. For example in the initial position, 1.(c1)c2 is safe while 1.axb3
+ will be valid only if black plays 1...Nb3.
+
+p Resolving rules:
+ul
+ li.
+ If both moves are illegal none are played.
+ If one is illegal, the other is played.
+ li.
+ If both moves arrive on the same square, both pieces disappear except
+ if one is a horseman and the other a footman.
+ In this case only the horseman remains.
+ li.
+ If a capture was intended but the target moved, the move is still played
+ but doesn't capture anything.
+
+figure.diagram-container
+ .diagram
+ | fen:npppn/p4/4P/P2pP/NPP1N:
+ figcaption After 1.d1d2 e4e3 2.dxe3 exd2, pawns placements are inversed.
+
+h3 Pawn promotions
+
+p.
+ Pawns automatically promote in a knight, except if the player already
+ have two horsemen on the board. In this case the footman is relocated on
+ any free square which is not on last rank.
+
+h3 End of the game
+
+p.
+ As stated previously, losing all pawns lose the game, so promoting your
+ last pawn loses. It may be the only legal move.
+ If however both footmen armies vanish at the same time, it's a draw.
+ It can happen if the two last pawns decide to advance to the same square.
+
+h3 Source
+
+p
+ a(href="https://www.chessvariants.com/rules/apocalypse") Apocalypse chess
+ | on chessvariants.com. This variant is playable at
+ a(href="http://apocalypsechess.online/") apocalypsechess.online
+ | but without the promotion restriction.
+
+p Inventor: C.S. Elliott (1976)
--- /dev/null
+import { ChessRules } from "@/base_rules";
+import { randInt } from "@/utils/alea";
+
+export class ApocalypseRules extends ChessRules {
+ static get PawnSpecs() {
+ return Object.assign(
+ {},
+ ChessRules.PawnSpecs,
+ {
+ twoSquares: false,
+ promotions: [V.KNIGHT]
+ }
+ );
+ }
+
+ static get HasCastle() {
+ return false;
+ }
+
+ static get HasEnpassant() {
+ return false;
+ }
+
+ static get CanAnalyze() {
+ return false;
+ }
+
+ static get ShowMoves() {
+ return "byrow";
+ }
+
+ static get PIECES() {
+ return [V.PAWN, V.KNIGHT];
+ }
+
+ static IsGoodPosition(position) {
+ if (position.length == 0) return false;
+ const rows = position.split("/");
+ if (rows.length != V.size.x) return false;
+ // At least one pawn per color
+ let pawns = { "p": 0, "P": 0 };
+ for (let row of rows) {
+ let sumElts = 0;
+ for (let i = 0; i < row.length; i++) {
+ if (['P','p'].includes(row[i])) pawns[row[i]]++;
+ if (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(pawns).some(v => v == 0))
+ return false;
+ return true;
+ }
+
+ static IsGoodFen(fen) {
+ if (!ChessRules.IsGoodFen(fen)) return false;
+ const fenParsed = V.ParseFen(fen);
+ // 4) Check whiteMove
+ if (
+ (
+ fenParsed.turn == "w" &&
+ // NOTE: do not check really JSON stringified move...
+ (!fenParsed.whiteMove || fenParsed.whiteMove == "-")
+ )
+ ||
+ (fenParsed.turn == "b" && fenParsed.whiteMove != "-")
+ ) {
+ return false;
+ }
+ return true;
+ }
+
+ static IsGoodFlags(flags) {
+ return !!flags.match(/^[0-2]{2,2}$/);
+ }
+
+ aggregateFlags() {
+ return this.penaltyFlags;
+ }
+
+ disaggregateFlags(flags) {
+ this.penaltyFlags = flags;
+ }
+
+ static ParseFen(fen) {
+ const fenParts = fen.split(" ");
+ return Object.assign(
+ ChessRules.ParseFen(fen),
+ { whiteMove: fenParts[4] }
+ );
+ }
+
+ static get size() {
+ return { x: 5, y: 5 };
+ }
+
+ static GenRandInitFen() {
+ return "npppn/p3p/5/P3P/NPPPN w 0 00 -";
+ }
+
+ getFen() {
+ return super.getFen() + " " + this.getWhitemoveFen();
+ }
+
+ getFenForRepeat() {
+ return super.getFenForRepeat() + "_" + this.getWhitemoveFen();
+ }
+
+ getFlagsFen() {
+ return this.penaltyFlags.join("");
+ }
+
+ setOtherVariables(fen) {
+ const parsedFen = V.ParseFen(fen);
+ this.setFlags(parsedFen.flags);
+ // Also init whiteMove
+ this.whiteMove =
+ parsedFen.whiteMove != "-"
+ ? JSON.parse(parsedFen.whiteMove)
+ : null;
+ }
+
+ setFlags(fenflags) {
+ this.penaltyFlags = [0, 1].map(i => parseInt(fenflags[i]));
+ }
+
+ getWhitemoveFen() {
+ if (!this.whiteMove) return "-";
+ return JSON.stringify({
+ start: this.whiteMove.start,
+ end: this.whiteMove.end,
+ appear: this.whiteMove.appear,
+ vanish: this.whiteMove.vanish
+ });
+ }
+
+ getSpeculations(moves, sq) {
+ let moveSet = {};
+ moves.forEach(m => {
+ const mHash = "m" + m.start.x + m.start.y + m.end.x + m.end.y;
+ moveSet[mHash] = true;
+ });
+ const color = this.turn;
+ this.turn = V.GetOppCol(color);
+ const oppMoves = super.getAllValidMoves();
+ this.turn = color;
+ // For each opponent's move, generate valid moves [from sq]
+ let speculations = [];
+ oppMoves.forEach(m => {
+ V.PlayOnBoard(this.board, m);
+ const newValidMoves =
+ !!sq
+ ? super.getPotentialMovesFrom(sq)
+ : super.getAllValidMoves();
+ newValidMoves.forEach(vm => {
+ const mHash = "m" + vm.start.x + vm.start.y + vm.end.x + vm.end.y;
+ if (!moveSet[mHash]) {
+ moveSet[mHash] = true;
+ vm.illegal = true; //potentially illegal!
+ speculations.push(vm);
+ }
+ });
+ V.UndoOnBoard(this.board, m);
+ });
+ return speculations;
+ }
+
+ getPossibleMovesFrom([x, y]) {
+ const possibleMoves = super.getPotentialMovesFrom([x, y])
+ // Augment potential moves with opponent's moves speculation:
+ return possibleMoves.concat(this.getSpeculations(possibleMoves, [x, y]));
+ }
+
+ getAllValidMoves() {
+ // Return possible moves + potentially valid moves
+ const validMoves = super.getAllValidMoves();
+ return validMoves.concat(this.getSpeculations(validMoves));
+ }
+
+ addPawnMoves([x1, y1], [x2, y2], moves) {
+ let finalPieces = [V.PAWN];
+ const color = this.turn;
+ const lastRank = (color == "w" ? 0 : V.size.x - 1);
+ if (x2 == lastRank) {
+ // If 0 or 1 horsemen, promote in knight
+ let knightCounter = 0;
+ let emptySquares = [];
+ 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) emptySquares.push([i, j]);
+ else if (
+ this.getColor(i, j) == color &&
+ this.getPiece(i, j) == V.KNIGHT
+ ) {
+ knightCounter++;
+ }
+ }
+ }
+ if (knightCounter <= 1) finalPieces = [V.KNIGHT];
+ else {
+ // Generate all possible landings
+ emptySquares.forEach(sq => {
+ if (sq[0] != lastRank)
+ moves.push(this.getBasicMove([x1, y1], [sq[0], sq[1]]));
+ });
+ return;
+ }
+ }
+ let tr = null;
+ for (let piece of finalPieces) {
+ tr = (piece != V.PAWN ? { c: color, p: piece } : null);
+ moves.push(this.getBasicMove([x1, y1], [x2, y2], tr));
+ }
+ }
+
+ filterValid(moves) {
+ // No checks:
+ return moves;
+ }
+
+ atLeastOneMove(color) {
+ const curTurn = this.turn;
+ this.turn = color;
+ const res = super.atLeastOneMove();
+ this.turn = curTurn;
+ return res;
+ }
+
+ // White and black (partial) moves were played: merge
+ resolveSynchroneMove(move) {
+ let m = [this.whiteMove, move];
+ for (let i of [0, 1]) {
+ if (!!m[i].illegal) {
+ // Either an anticipated capture of something which didn't move
+ // (or not to the right square), or a push through blocus.
+ if (
+ (
+ // Push attempt
+ m[i].start.y == m[i].end.y &&
+ (m[1-i].start.x != m[i].end.x || m[1-i].start.y != m[i].end.y)
+ )
+ ||
+ (
+ // Capture attempt
+ Math.abs(m[i].start.y - m[i].end.y) == 1 &&
+ (m[1-i].end.x != m[i].end.x || m[1-i].end.y != m[i].end.y)
+ )
+ ) {
+ // Just discard the move, and add a penalty point
+ this.penaltyFlags[m[i].vanish[0].c]++;
+ m[i] = null;
+ }
+ }
+ }
+
+ // For PlayOnBoard (no need for start / end, irrelevant)
+ let smove = {
+ appear: [],
+ vanish: []
+ };
+ const m1 = m[0],
+ m2 = m[1];
+ // If one move is illegal, just execute the other
+ if (!m1 && !!m2) return m2;
+ if (!m2 && !!m1) return m1;
+ if (!m1 && !m2) return smove;
+ // Both move are now legal:
+ smove.vanish.push(m1.vanish[0]);
+ smove.vanish.push(m2.vanish[0]);
+ if ((m1.end.x != m2.end.x) || (m1.end.y != m2.end.y)) {
+ // Easy case: two independant moves
+ smove.appear.push(m1.appear[0]);
+ smove.appear.push(m2.appear[0]);
+ // "Captured" pieces may have moved:
+ if (
+ m1.vanish.length == 2 &&
+ (
+ m1.vanish[1].x != m2.start.x ||
+ m1.vanish[1].y != m2.start.y
+ )
+ ) {
+ smove.vanish.push(m1.vanish[1]);
+ }
+ if (
+ m2.vanish.length == 2 &&
+ (
+ m2.vanish[1].x != m1.start.x ||
+ m2.vanish[1].y != m1.start.y
+ )
+ ) {
+ smove.vanish.push(m2.vanish[1]);
+ }
+ } else {
+ // Collision: both disappear except if different kinds (knight remains)
+ const p1 = m1.vanish[0].p;
+ const p2 = m2.vanish[0].p;
+ if ([p1, p2].includes(V.KNIGHT) && [p1, p2].includes(V.PAWN)) {
+ smove.appear.push({
+ x: m1.end.x,
+ y: m1.end.y,
+ p: V.KNIGHT,
+ c: (p1 == V.KNIGHT ? 'w' : 'b')
+ });
+ }
+ }
+ return smove;
+ }
+
+ play(move) {
+ // Do not play on board (would reveal the move...)
+ move.flags = JSON.stringify(this.aggregateFlags());
+ this.turn = V.GetOppCol(this.turn);
+ this.movesCount++;
+ this.postPlay(move);
+ }
+
+ postPlay(move) {
+ if (this.turn == 'b') {
+ // NOTE: whiteMove is used read-only, so no need to copy
+ this.whiteMove = move;
+ return;
+ }
+
+ // A full turn just ended:
+ const smove = this.resolveSynchroneMove(move);
+ V.PlayOnBoard(this.board, smove);
+ move.whiteMove = this.whiteMove; //for undo
+ this.whiteMove = null;
+ move.smove = smove;
+ }
+
+ undo(move) {
+ this.disaggregateFlags(JSON.parse(move.flags));
+ if (this.turn == 'w')
+ // Back to the middle of the move
+ V.UndoOnBoard(this.board, move.smove);
+ this.turn = V.GetOppCol(this.turn);
+ this.movesCount--;
+ this.postUndo(move);
+ }
+
+ postUndo(move) {
+ if (this.turn == 'w') this.whiteMove = null;
+ else this.whiteMove = move.whiteMove;
+ }
+
+ getCheckSquares(color) {
+ return [];
+ }
+
+ getCurrentScore() {
+ if (this.turn == 'b')
+ // Turn (white + black) not over yet
+ return "*";
+ // Count footmen: if a side has none, it loses
+ let fmCount = { 'w': 0, 'b': 0 };
+ for (let i=0; i<5; i++) {
+ for (let j=0; j<5; j++) {
+ if (this.board[i][j] != V.EMPTY && this.getPiece(i, j) == V.PAWN)
+ fmCount[this.getColor(i, j)]++;
+ }
+ }
+ if (Object.values(fmCount).some(v => v == 0)) {
+ if (fmCount['w'] == 0 && fmCount['b'] == 0)
+ // Everyone died
+ return "1/2";
+ if (fmCount['w'] == 0) return "0-1";
+ return "1-0"; //fmCount['b'] == 0
+ }
+ // Check penaltyFlags: if a side has 2 or more, it loses
+ if (this.penaltyFlags.every(f => f == 2)) return "1/2";
+ if (this.penaltyFlags[0] == 2) return "0-1";
+ if (this.penaltyFlags[1] == 2) return "1-0";
+ if (!this.atLeastOneMove('w') || !this.atLeastOneMove('b'))
+ // Stalemate (should be very rare)
+ return "1/2";
+ return "*";
+ }
+
+ getComputerMove() {
+ const maxeval = V.INFINITY;
+ const color = this.turn;
+ let moves = this.getAllValidMoves();
+ if (moves.length == 0)
+ // TODO: this situation should not happen
+ return null;
+
+ if (Math.random() < 0.5)
+ // Return a random move
+ return moves[randInt(moves.length)];
+
+ // Rank moves at depth 1:
+ // try to capture something (not re-capturing)
+ moves.forEach(m => {
+ V.PlayOnBoard(this.board, m);
+ m.eval = this.evalPosition();
+ V.UndoOnBoard(this.board, m);
+ });
+ moves.sort((a, b) => {
+ return (color == "w" ? 1 : -1) * (b.eval - a.eval);
+ });
+ let candidates = [0];
+ for (let i = 1; i < moves.length && moves[i].eval == moves[0].eval; i++)
+ candidates.push(i);
+ return moves[candidates[randInt(candidates.length)]];
+ }
+
+ getNotation(move) {
+ // Basic system: piece + init + dest square
+ return (
+ move.vanish[0].p.toUpperCase() +
+ V.CoordsToSquare(move.start) +
+ V.CoordsToSquare(move.end)
+ );
+ }
+};
});
}
- // NOTE: lazy unefficient implementation (for now. TODO?)
getPossibleMovesFrom([x, y]) {
- const moves = this.getAllValidMoves();
- return moves.filter(m => {
- return m.start.x == x && m.start.y == y;
- });
+ return (
+ this.filterValid(super.getPotentialMovesFrom([x, y]))
+ // Augment with potential recaptures:
+ .concat(this.getRecaptures())
+ );
}
// Aux function used to find opponent and self captures
return this.filterValid(moves);
}
- getAllValidMoves() {
- const color = this.turn;
- // 0) Generate our possible moves
- let myMoves = super.getAllValidMoves();
+ getRecaptures() {
// 1) Generate all opponent's capturing moves
let oppCaptureMoves = [];
+ const color = this.turn;
const oppCol = V.GetOppCol(color);
for (let i=0; i<8; i++) {
for (let j=0; j<8; j++) {
// 2) Play each opponent's capture, and see if back-captures are possible:
// Lookup table to quickly decide if a move is already in list:
let moveSet = {};
+ let moves = [];
oppCaptureMoves.forEach(m => {
// If another opponent capture with same endpoint already processed, skip:
const mHash = "m" + m.end.x + m.end.y;
};
V.PlayOnBoard(this.board, justDisappear);
// Can I take on [m.end.x, m.end.y] ? If yes, add to list:
- this.getCaptures(m.end.x, m.end.y, color).forEach(cm => myMoves.push(cm));
+ this.getCaptures(m.end.x, m.end.y, color).forEach(cm => moves.push(cm));
V.UndoOnBoard(this.board, justDisappear);
}
});
- return myMoves;
+ return moves;
+ }
+
+ getAllValidMoves() {
+ // Return possible moves + potential recaptures
+ return super.getAllValidMoves().concat(this.getRecaptures());
}
filterValid(moves) {
this.undo(lastMove); //will erase whiteMove, thus saved above
}
let res = [];
- if (this.underCheck('w'))
+ if (this.kingPos['w'][0] >= 0 && this.underCheck('w'))
res.push(JSON.parse(JSON.stringify(this.kingPos['w'])));
- if (this.underCheck('b'))
+ if (this.kingPos['b'][0] >= 0 && this.underCheck('b'))
res.push(JSON.parse(JSON.stringify(this.kingPos['b'])));
if (color == 'b') this.play(lastMove);
return res;
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