TODO

   1 PROBABLY WON'T FIX:
   2 Embedded rules language not updated when language is set (in Analyse, Game and Problems)
   3 If new live game starts in background, "new game" notify OK but not first move.
   4
   5 "FreeBoard", re-using a lot of Board logic, but with SVG (empty) board + SVG (empty) reserves.
   6 Will be used for variants with custom non-rectangular board (Hex, at least)
   7 Or, with other board shapes (see greenchess.net for example)
   8
   9 Merge Orda + Empire + Hoppelpoppel + Newzealand getSlideNJumpMoves() into base_rules.js
  10 => allow to simplify getPawnMoves in RoyalRace (and some getXMoves in Shatranj)
  11
  12 Option "free placement" in Hidden
  13
  14 #New variants:
  15 Chessplode
  16 Tablut
  17
  18 https://brainking.com/fr/GameRules?tp=128 Massacre Chess
  19
  20 PizzaKings https://www.chessvariants.com/unequal.dir/pizza-kings.html
  21 https://en.m.wikipedia.org/wiki/Chess_with_different_armies#Pizza_Kings%5B11%5D_(John_Lawson)
  22
  23 Coin Chess
  24 https://msoworld.com/product/chess-variants/
  25 Background: Unknown inventor
  26 Rules:
  27 Normal rules apply except for the introduction of a coin (or counter)
  28 Black starts by placing the coin on any unoccupied square. Play then continues with players alternating turns as in normal chess.
  29 On their turn, a player makes any legal move but may not move onto the square where the coin has been placed. The player may move over (but not onto), the coin square.
  30 The player ends their turn by leaving the coin where it stands or moving the coin to a different unoccupied square.
  31 The coin can never be placed on an occupied square, and therefore cannot be used to protect a piece from capture
  32 A player wins by checkmating the opponent. Note that the coin can be used to remove escape squares from the king.
  33
  34 https://www.chessvariants.com/other.dir/nemoroth.html :-)