Standard chess, projected across stacked rhombus boards. Every rule you already know — plus one new axis.
All pieces — King, Queen, Rook, Bishop, Knight, Pawn — move identically to standard chess within a single level. Rooks slide along ranks and files, bishops on diagonals, knights jump in their L-shape, and so on.
If you know chess, you already know 80% of Rhombus.
Pieces can jump between adjacent levels as part of their normal movement. A bishop on Level L can move to a diagonal square on L−1 or L+1, provided no piece blocks the corresponding square on its starting level.
Think of each level as a transparent floor: you don't move through levels — you arrive on one.
Captures work exactly like movement. If your destination square — on any reachable level — contains an enemy piece, that piece is captured.
You cannot capture through your own pieces. A friendly blocker on the starting-level square invalidates the level transition.
Pawns advance one square forward as in standard chess, but on each move may also shift one level up or down. Diagonal captures follow the same rule and may be made on the level above or below.
Pawns may travel both directions on the level axis — there is no "back rank" along the vertical.
A pawn promotes when it reaches column 7 — the last column of its starting level — regardless of which level it currently occupies. Promote to Queen, Rook, Bishop, or Knight.
Castling is permitted only within a single level — both King and Rook must be on the same level, neither has moved, and no piece (on any level) attacks the King's path.
The King is in check whenever any enemy piece — on any level — could legally capture it next turn. Checkmate occurs when no legal move resolves the check, including level shifts.
Always check the levels above and below before declaring safety.
If the player to move has no legal move and is not in check, the game is a draw. Because pieces can shift levels, true stalemates are rarer than in standard chess — but they happen.
7-level (Classic): tighter stack, faster matches, single-step level shifts only.
15-level (Grandmaster): larger stack with the same per-move shift rule. Long-range pieces gain enormous reach over the course of a match. Tournament-rated.