- TODO: explain, every turn twice except if check on 1st turn, or
- very first move in game.
- En-passant: possible in any order if 2 ep squares,
- otherwise has to be the first move.
- OK even if opponent moved his pawn at subturn 1.
+ At the very first move of the game, white make only one move - as usual.
+ However, after that and for all the game each side must play twice at
+ every turn. There are two exceptions:
+
+ul
+ li.
+ If the first move gives check (maybe checkmate),
+ then a second move isn't played.
+ li.
+ If no move is available after the first move, then it's stalemate
+ and again, there is no second move.
+
+p.
+ About the PGN game notation: when a side plays two moves in a row,
+ they are separated (in order) by a comma in the PGN.
+ Example: 3.Na5,Bd3 e6,f4 (the two first are white moves,
+ the two others are black moves).