This is the game they play on Gallifrey, to teach young Time Lords how to start thinking along timelines, instead of within timelines.
The Short Game of Causality is played on 22boards. The long game is played on 1,534. The boards are arranged above and below a line called the Horizon. Below the Horizon is the Point of Origin board. This board has two generations; each of these boards has two generations, and (in the short game), each of these boards has two generations, for a total of fifteen.
Above the Horizon there are seven more boards. The first four each have two progenitor boards, the next two likewise, and the final board (the Singularity) similarly.
sketch; board layout is not accurate
Each board is six squares by six squares, and contains six pieces for each player (Black and White). The six pieces are the Regent, the Regis, two Castles, and two Elephants.
Each board also has an Orientation: a board is either Orthodox or Unorthodox. At the start of the game, the Point of Origin is Orthodox, and the Singularity is Unorthodox. On an Orthodox board, Elephants behave like bishops (long diagonal movements only), and Castles behave like pawns (advancing one square, attacking on the diagonal). On an Unorthodox board, Elephants behave like pawns, and Castles behave like knights (advancing two squares up and one to the side). The Regent and Regis always behave like the king and queen, but swap places when the board changes its orientation.
A player is able to make one move each on two separate boards per turn.
At the outset of the game, half of the boards are Orthodox, and half are Unorthodox. Each pair of boards is in the Obverse Arrangement. When Black puts White in check on any board below the Horizon, the orientations of that board’s generation are swapped to Reverse alignment — the Orthodox board is now unorthodox, and vice-versa. When White puts Black in check, the orientations return to Obverse.
Above the Horizon, a board’s orientation is determined by its progenitor boards — if they are the same, the board remains in its Obverse alignment. If they are different, the board changes to its Reverse alignment.
When a Regent is in checkmate, the board is Locked, and no further moves on that board can be played (however, moves on boards closer to the Point of Origin CAN be played; if the board’s orientation changes and checkmate is disrupted, the board is Unlocked and can be played again.
The game is won by creating checkmate on the Singularity board.
[POSSIBLY: there are only four pieces per player per board (Regent, Regis, Elephant, and Castle), arranged in opposite corners.
POSSIBLY: The game ends when checkmate on the Singularity is achieved, and no further moves on previous boards can be made; the player wins who has the most points — the Singularity is worth five points, the individual boards are worth one point each.
am still working out the details]