--- title: "Raumschach" slug: raumschach board: "5×5×5 (3D)" players: "2" parent: chess win: "Checkmate" special: "Three-dimensional chess on five stacked 5×5 boards. Adds the Unicorn (triagonal slider). Pawns move forward or upward; capture diagonally. No castling, no en passant, no double push." engine: topology: type: grid rows: 5 cols: 5 layers: 5 layer_labels: ["A", "B", "C", "D", "E"] players: [white, black] setup: - "5/5/5/PPPPP/RNKNR" - "5/5/5/PPPPP/BUQBU" - "5/5/5/5/5" - "buqbu/ppppp/5/5/5" - "rnknr/ppppp/5/5/5" render: cellSize: 24 notation: level-file-rank rendering_note: "This layered setup uses the same engine.topology pattern already live for Gygax Chess (grid + layers, one FEN string per layer) and should render the static starting-position diagram now, the same way Gygax's is rendered. This does NOT solve piece movement/play: Raumschach's Rook, Bishop, and Unicorn slide arbitrary distances along the level axis and combinations of axes, which Gygax's per-piece single-step cross-level moves do not support. Play/move-generation remains a separate, larger engine task -- this frontmatter change only unblocks the rulebook diagram." published: true status: draft updated: 2026-07-16 category: expanded-boards order: tags: - 3d - spatial - unicorn - historical --- # 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(c), Knight(d), Rook(e) **Level A, Rank 2:** five Pawns (Aa2–Ae2) **Level B, Rank 1:** Bishop(a), Unicorn(b), Queen(c), 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(c), Bishop(d), Unicorn(e) **Level D, Rank 4:** five Pawns (Da4–De4) **Level E, Rank 5:** Rook(a), Knight(b), King(c), 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.