Chess · Variant 116 of 153

Raumschach

5×5×5 (3D)Board 2Players

Raumschach

Raumschach (“Space Chess” in German) is a three-dimensional chess variant invented by Ferdinand Maack in 1907. It is played on five stacked 5×5 boards, each called a level, giving a total space of 5×5×5 = 125 squares. Raumschach adds one new piece to the standard set: the Unicorn, which slides along the triagonal axes of the three-dimensional board.

The Board

The board consists of five levels, labelled A through E from bottom (White’s side) to top (Black’s side). Each level is a 5×5 grid with files a–e and ranks 1–5.

Squares are written as Level + file + rank. For example, Bc3 means Level B, file c, rank 3. Aa1 is the bottom-left corner of the lowest level.

White’s pieces occupy levels A and B at the start; Black’s occupy levels D and E. Level C is empty.

Starting Position

White (ranks 1–2 of levels A and B)

Level A, Rank 1: Rook(a), Knight(b), King©, Knight(d), Rook(e) Level A, Rank 2: five Pawns (Aa2–Ae2)

Level B, Rank 1: Bishop(a), Unicorn(b), Queen©, Bishop(d), Unicorn(e) Level B, Rank 2: five Pawns (Ba2–Be2)

Black (ranks 4–5 of levels D and E)

Level D, Rank 5: Bishop(a), Unicorn(b), Queen©, Bishop(d), Unicorn(e) Level D, Rank 4: five Pawns (Da4–De4)

Level E, Rank 5: Rook(a), Knight(b), King©, Knight(d), Rook(e) Level E, Rank 4: five Pawns (Ea4–Ee4)

Each side begins with 20 pieces: 2 Rooks, 2 Knights, 2 Bishops, 2 Unicorns, 1 Queen, 1 King, and 10 Pawns.

The engine.setup array above encodes this as one FEN-style row-group per level (A through E), matching the pattern already proven for Gygax Chess’s three-level board, using U for Unicorn to avoid clashing with Knight’s standard N.

Piece Movement

In three-dimensional chess, movement is defined by how many of the three axes (rank, file, level) change simultaneously:

  • Orthogonal (1 axis): only rank, only file, or only level changes
  • Diagonal (2 axes): any two axes change simultaneously
  • Triagonal (3 axes): all three axes change simultaneously, one step each

Rook

Slides any number of squares along a single axis (rank, file, or level). Cannot jump over pieces. In 3D space the Rook has 6 orthogonal sliding directions (±rank, ±file, ±level).

Bishop

Slides any number of squares along a two-axis diagonal (rank+file, rank+level, or file+level, in any combination of signs). Cannot jump over pieces. In 3D space the Bishop has 12 diagonal sliding directions.

Unicorn (U)

The Unicorn slides any number of squares along a triagonal — moving simultaneously one step in all three axes with each step. Cannot jump over pieces. In 3D space the Unicorn has 8 triagonal directions (all 8 combinations of ±rank, ±file, ±level).

The Unicorn is colour-bound within the 3D lattice: on a 5×5×5 board, triagonals partition squares into two disjoint sets. A Unicorn can never change its triagonal colour.

Queen

Combines the Rook and Bishop (orthogonal and two-axis diagonal slides). Does not include the Unicorn’s triagonal move. Cannot jump over pieces.

Knight

Leaps to any square exactly 2 steps in one axis and 1 step in another (the standard chess knight jump, extended to 3D). This gives up to 24 destinations from a central square. Always jumps over intervening pieces.

King

Moves one step in any direction — orthogonal, two-axis diagonal, or triagonal — giving up to 26 possible destinations from an interior square. Cannot move into check.

Pawn

White Pawns move toward Black’s starting area (increasing rank and/or increasing level).

Non-capturing moves (White):

  • Straight-forward: advance one rank on the same level (e.g., Aa2 → Aa3)
  • Straight-upward: advance one level at the same file and rank (e.g., Aa2 → Ba2)

Capturing moves (White):

  • Diagonally-forward: advance one rank while also moving one step in file (same level, e.g., Aa2 → Ab3)
  • Diagonally-forward-upward: advance one rank and one level simultaneously (e.g., Aa2 → Bb3)

Black Pawns move in the opposite direction (decreasing rank and/or decreasing level), with equivalent capture directions.

Pawn rules:

  • No initial two-square advance. All Pawn moves are one step.
  • No en passant.
  • White Pawns promote on rank 5 of level A or B. Black Pawns promote on rank 1 of level D or E. Pawns that move into levels C, D, or E without reaching rank 5 of a qualifying level do not promote there.

Special Rules

  • No castling.
  • No en passant.
  • No double pawn push.
  • Stalemate is a draw.

Notation

Squares are written as Level (A–E), file (a–e), rank (1–5). Examples:

  • Aa1 — Level A, file a, rank 1 (White’s back-left corner)
  • Bc3 — Level B, file c, rank 3 (centre of level B)
  • Ec5 — Level E, file c, rank 5 (Black’s back-centre)

Moves: piece letter, origin square, hyphen, destination. Example: R Aa1–Aa4 (Rook from Aa1 to Aa4).

Attribution

Raumschach was invented by Ferdinand Maack (Germany, 1907). Rules sourced from The Chess Variant Pages at chessvariants.com/3d.dir/3d5.html.