Few rules. Severe consequences.

Every legal result follows from the movement phase, the optional rebuild, the composition limits, and the real ability to concentrate four flexible cubes above one surviving foundation.

Loss is immediate

A player who can no longer build a five-cube king loses immediately, even if the opponent has not yet built a king. Only if both players are unable to build a king is the result a draw.

The bottom cube is committed

A single height-1 cube cannot be removed from the board or returned to reserve. Only the top cube of a height-2–4 piece may return. A built king can never be dismantled.

OFFICIAL RULES

The king must be built — victory must be earned.

Cubic Chess is played on a classical 8×8 board. Each side controls 24 cubes: 16 begin on the first two ranks and eight form the reserve.

Figures and promotion

Height 1 is a pawn-cube, 2 a bishop, 3 a rook, 4 a queen, and 5 a king. On the last rank the player must choose any legal figure except a king: bishop, rook, or queen, using 1, 2, or 3 reserve cubes. If no option is legal, the move is illegal.

A complete turn

First move one figure. Then, optionally, add exactly one reserve cube, return exactly one top cube from a height-2–4 figure, or make no rebuild. A height-1 figure cannot be removed or sent to reserve. Mandatory pawn promotion is the sole special transformation and ends the turn immediately; it cannot be followed by another add or removal.

Composition limits

Each side may have at most two bishops, two rooks, one queen, and one king at a time. Two bishops of the same side must stand on opposite-coloured squares; a second bishop on the same colour cannot be built, obtained by dismantling, or chosen in promotion.

The inviolable king

A player cannot win until their own king appears. The king is never captured: it is checkmated. Its top cube cannot be removed, so a built king cannot be dismantled.

Victory

Win by checkmating the opposing king. A player who can no longer build a five-cube king loses immediately, even if the opponent has not yet built one; if neither side can build a king, the game is drawn.

Draw

A draw is recorded on the third occurrence of the same complete position, or when neither player retains enough cubes to build a king. A position with no legal move and no valid winner is also a draw.

OBJECTIVE

Five heights, five capabilities

Pawn

moves like a pawn and must promote on the last rank

Bishop

moves diagonally

Rook

moves along ranks and files

Queen

moves along every straight line

King

moves one square