The gameplay is just like chess, with King Neptune being the King. The player must protect King Neptune from losing. Standard chess rules apply to this game, with some exceptions, such as the fact that sometimes the opposite player ("black") starts.
Modes
Single-player
Two-player
In single-player mode, the player must defeat a computer at chess, with different intelligence depending on the computer's level. To win the best score, as little number of moves and lost pieces must be done (though the "point rule" in chess doesn't apply here).
There are various exceptions to the standard chess rules including...
On occasions the opposite team ("black") starts.
The fact that the player can "checkmate" by capturing all of the opponent's pieces.
On single-player mode, the player always plays on White's side, never on Black's side.
It is possible to castle in or through check, despite that being impossible in chess.
There are various achievements for certain "special" chess tactics:
"Passing the Pawn" - an achievement for capturing a pawn en passant in single-player mode.
"Save the Queen" - an achievement for capturing the king but preserving the queen.
"Fortify the Walls" - an achievement for castling in single-player mode (whether it be kingside castling or queenside castling).
"Promotion" - an achievement for promotion of a pawn (making a pawn reach the eighth rank and thus allowing promoting the pawn to a knight, bishop, rook or queen)
