| 1 | p.boxed |
| 2 | | Both players play a move "at the same time". |
| 3 | | Conflicts are resolved following a few simple rules. |
| 4 | |
| 5 | p. |
| 6 | In order to not rethink a big part of the code, the white move has to be |
| 7 | played before the black one. However, the black player doesn't see it. |
| 8 | |
| 9 | p So both players play "at the same time". Resolving rules: |
| 10 | ul |
| 11 | li. |
| 12 | If both moves arrive on the same square, both pieces disappear except |
| 13 | if one is a king. In this case only the king remains. |
| 14 | li. |
| 15 | If a capture was intended but the target moved, the move is still played |
| 16 | but doesn't capture anything. |
| 17 | p. |
| 18 | Such captures can be anticipated by capturing our own pieces. |
| 19 | If the enemy captures as predicted, his piece disappears. |
| 20 | If he doesn't, the self-capture isn't undone. |
| 21 | |
| 22 | figure.diagram-container |
| 23 | .diagram |
| 24 | | fen:rnb1kbnr/ppp1pppp/8/3qP3/8/8/PPPP1PPP/RNBQKBNR: |
| 25 | figcaption After 1.e4 d5 2.e5 Qxd5 (anticipating 2.exd5 which isn't played) |
| 26 | |
| 27 | p. |
| 28 | When the king is under check, a legal orthodox move must be played. |
| 29 | Some weird situations would occur otherwise, like on the following diagram. |
| 30 | If we allow self-(re)captures then the king would take on h2 and escape to |
| 31 | the third rank. |
| 32 | |
| 33 | figure.diagram-container |
| 34 | .diagram |
| 35 | | fen:7k/8/8/3QR3/3P4/4P3/r6P/q6K: |
| 36 | figcaption 1.Kxh2 by anticipation isn't allowed: white is checkmated. |
| 37 | |
| 38 | h3 End of the game |
| 39 | |
| 40 | p. |
| 41 | Due to the simultaneity, it is possible that a king is captured for example |
| 42 | after escaping a check in a wrong way, as the following diagram shows. |
| 43 | So, capturing the king counts as a win, of highest priority. |
| 44 | A checkmate wins too, but if your king is captured and the other still on |
| 45 | the board (even if it is mated), you lose. |
| 46 | |
| 47 | figure.diagram-container |
| 48 | .diagram.diag12 |
| 49 | | fen:r3r1bb/ppqRkppp/8/2p1n3/7n/8/PPPPP1P1/RNBQNBK1: |
| 50 | .diagram.diag22 |
| 51 | | fen:r3r1bb/pp1qRppp/8/2p1n3/7n/8/PPPPP1P1/RNBQNBK1: |
| 52 | figcaption. |
| 53 | Left: before Rxe7 (white) and Qxd7 (black) |
| 54 | Right: after the move (1-0) |
| 55 | |
| 56 | h3 Source |
| 57 | |
| 58 | p |
| 59 | a(href="http://www.hexenspiel.de/engl/synchronous-chess/") Synchronous chess |
| 60 | | , modified to allow en-passant captures |
| 61 | | and disable the "exchange of captures" stage. |
| 62 | a(href="http://www.pion.ch/echecs/variante.php?jeu=synchro") |
| 63 | | Another description |
| 64 | | . |