However, the advance of the game is so slow, that in the c. 20 games I played, I never gave a checkmate to anyone; all the games either finished by being suspended, or by the opponent's resignation.
The initial setup is:
a b c d e f g h i j k l m n o p +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ 8 | r | n | n | r | | b | k | q | b | | b | c | c | b | | r | n | n | r | 8 +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ 7 | p | p | p | p | | p | p | p | p | | p | p | p | p | | p | p | p | p | 7 +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ 6 | | | | | | | | | | | | | | | | | | | | 6 +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ 5 | | | | | | | | | | | | | | | | | | | | 5 +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ 4 | | | | | | | | | | | | | | | | | | | | 4 +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ 3 | | | | | | | | | | | | | | | | | | | | 3 +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ 2 | P | P | P | P | | P | P | P | P | | P | P | P | P | | P | P | P | P | 2 +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ 1 | R | N | N | R | | B | K | Q | B | | B | C | C | B | | R | N | N | R | 1 +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ +---+---+---+---+ a b c d e f g h i j k l m n o pC = Cardinal; all other pieces have the same name as Orthochess.
The game has rotational symmetry: if the King, Queen, and the King's Pawn are coplanar, so are the King, King's Knight and King's Pawn. In other words, the game would be exactly the same if, instead of the design, above, the columns were placed in the order (a,e,i,m), (b,f,j,n), (c,g,k,o), (d,h,l,p).
If we look from the White's side, the board would look like this:
+---+---+---+---+ | R | N | N | R | +---+---+---+---+ | B | C | C | B | +---+---+---+---+ | B | K | Q | B | +---+---+---+---+ | R | N | N | R | +---+---+---+---+
The exceptions were the Cardinal. (In Raumschach, or 5x5x5 Variant, this piece is the Unicorn), that would move in the long diagonals (example: a1 - f2 - k3 - p4), and the King and Queen, that would also get long-diagonal movements.
But, since the Cardinal would only control 1/4 of the squares, we decided to change the movements of the Cardinal for those of the Bishop. In this way, each one of the four bishops would control 1/4 of the squares, so that they, together, would control the whole board (it might even be possible to checkmate with K + B + B + B + B vs K).
(Afterthought: it would be more correct to change the display, replacing the B[ishop] by U[nicorn], and the C[ardinal] by B[ishop]...)
Notice that this game has potential for increasing, with some natural pieces, like two 3D Knights (1,1,2) or (1,2,2) or a 3D Pawn (fcTfmW)
So, the winning strategy is capture the other pieces, promote pawns to Queens, and, with massive material advantage, mate the King.
Since we are bound to 2D thinking, the Bishops become very powerful pieces, as soon as they are brought to the attack. The normal way of developing them is by fianchetto: b3 - B(e1)b2 - B(b2)l4, with pressure over g5 and b6; or by the central squares: j3 - B(e1)o3 or j3 - B(e1)j2 - B(j2)m3!. The Bishops are stronger when they are in the (a), (d), (m) or (p) columns, when they have maximum range.
The Knights are also very powerful (in an unbound board, each Knight would control 3! * 2 * 2 = 24 squares), and can be coordinated to assault the opponent's weak pawns. Since the limitations of the Board restrain the diagonal movements, the slowness of the Orthoknight is not inherited to 3D: the Knight is probably much stronger then the Cardinal, the Bishop and, maybe, the Rook.