gg³ — Rules

This is the application contract for Strato Chess strato-v1 and Chess³ chess3-v1. Interpretations and example outcomes were reviewed and approved by the project owner before engine implementation on 24 September 2026. Saved games permanently retain their ruleset and rules version. Changes to these rules require a new version.

Sources and notation#

• Triple S Games: Strato Chess demonstration, especially 0:28–0:49 (pawns), 1:59–2:18 (transfers), 2:19–2:45 (exceptions), and 3:05–3:12 (promotion).
• Classic Games Company Chess³ description, reproduced by Chess Variant Pages. Its promised diagrams are absent and its text contains OCR errors.

These explanations are written for this application. The conventions below are not claims about historical rules.

Coordinates consist of level, file and rank: 2e4 means middle level, file e, rank 4. Levels are 1 (bottom), 2 (middle), 3 (top). All boards have identical orientation, with a1 dark. White advances toward rank 8; Black toward rank 1. White moves first, irrespective of the creator’s chosen color.

Algebraic move notation#

The interface uses algebraic notation with a Greek suffix on each destination: α is bottom (stored level 1), β is middle (2), and γ is top (3). Thus the stored coordinate 2e4 displays as e4β. Numeric coordinates in the technical examples below and in saved games remain unchanged. This is an application-specific 3D extension, not standard SAN or a claim of PGN compatibility.

Pieces use K/Q/R/B/N; pawns have no piece letter. Captures use x, including en passant. Pawn captures always include the origin file, even for Chess³ captures that keep the same file while changing levels. Promotion uses =Q, =R, =B or =N after the destination level. Castling uses O-O or O-O-O followed by the final level. Check appends +; checkmate appends #. Stalemate, timeout, resignation and agreed draws do not add a mate symbol.

When multiple pieces of the same type can legally reach the same full destination, add the first origin qualifier that distinguishes the move: file, rank, file+rank, level, file+level, rank+level, then file+rank+level. Pinned pieces and other illegal alternatives do not count. Examples include Nbd2α, N1d2α, Nb1d2α and Nαc3β (the knight from the bottom level). Pawn captures retain their mandatory file and try file+rank, file+level, then the full origin. Quiet pawns can also need qualifiers in 3D: αe4β distinguishes a pawn arriving from the bottom level from γe4β arriving from the top.

The formatter uses the position before each move and the resulting position. History is replayed under the saved ruleset to recover this context, so older games receive the same display without a database migration or a movement-rules version change. Promotion destinations show =… until a piece is chosen; the confirmation button then shows the complete notation for that choice.

3  Black: a8 R N B Q K B N R h8; pawns a7–h7
2  Empty
1  White: a1 R N B Q K B N R h1; pawns a2–h2

Vertical rook line: 1a4 → 2a4 → 3a4
Spatial bishop line: 1c1 → 2d2 → 3e3

Each side has the ordinary 16 pieces. The first diagram describes the complete opening for both versions. Placement on separate outer levels is shown by the Strato source; using this precise arrangement for Chess³ is our convention because its setup diagram is missing.

Strato v1#

Pieces retain ordinary same-level chess movement and capture. Each piece must change level on its first move, except when castling or making a same-level capture/block that resolves check. A quiet first king move that merely escapes on the same level is not an exception.

No move changing levels can capture. Every traversed transfer square and the destination must be empty. On one level, ordinary blockers and knight jumping apply.

For compound pawn, knight and first king moves, our convention resolves the vertical segment first, then the planar segment. The vertical path must be empty; the final square must be empty; forward pawn steps must also be clear. Knights jump over planar blockers. Only the final position determines check for ordinary moves; castling has the extra transit checks below.

Attacks are ordinary same-level chess attacks, independent of movement flags and whether the attacking side is in check. This is an explicit convention avoiding circular attack/legality definitions. Interlevel transfers do not attack; an enemy king on another level is not adjacent for Strato check purposes. Kings cannot be captured, and no move may leave one’s own king attacked.

Castling: apply ordinary castling on the original level, then optionally transfer both pieces to their corresponding castled squares one level above/below. Both pieces must be original and unmoved. Squares between king and rook must be empty. The king’s starting, transit and castled square on the original level must be safe; both transfer destinations must be empty and the final king square safe. This sequencing is our application convention. Moving either piece, including a transfer, permanently removes its associated castling right.

Chess³ v1#

There is no forced first-level-change rule. Quiet moves and captures use the same geometry except for pawns. Cross-level captures are permitted. Sliding pieces stop at the first occupied square; they may capture an enemy there but cannot pass through it. Knights jump.

Use displacements (file, rank, level):

The pawn’s quiet move is never a combination of forward and vertical motion. A vertical pawn move consumes its first-move privilege, even if it later returns. The eight capture destinations are an application interpretation of the description’s forward diagonals in the absence of its diagrams.

Use ordinary castling on the starting level and original rank only; no interlevel castling. Both original pieces must be unmoved, the path clear, and the king’s starting/transit/destination squares unattacked.

Shared special rules and endings#

• On reaching rank 8 (White) or 1 (Black) on any level, a pawn must promote immediately to queen, rook, bishop or knight. Promoted pieces count as moved and cannot gain castling privileges.
• En passant is allowed only immediately after a same-level two-rank pawn advance. The capturing pawn remains on that level, moves one rank diagonally forward into the passed square, and removes the adjacent pawn. A transfer or vertical double move never creates en passant rights. Strato’s first-move restriction still applies to the capturing pawn.
• Checkmate: the side to move is attacked and has no legal move. Stalemate: it has no legal move and is not attacked. Test all three levels for escapes.
• Players can resign or mutually agree a draw. A draw offer expires when either side makes a move; only the other player can accept it. Finished games cannot change.
• Repetition, move-count and material-based draw adjudication are deliberately absent from v1. No takebacks, spectators, matchmaking or account recovery. Match clocks are a separate contract described below.

Resolved ambiguities#

Approved fixture examples#

Full executable positions are in the engine fixture suite. Opening fixtures use the complete formation above. For isolated geometric fixtures, use White king 1h1, Black king 3h8, White to move, all listed pieces marked moved and all unlisted squares empty unless the fixture explicitly changes them. Castling fixtures instead place the White king on 1e1 and original rook on 1h1, both unmoved.

Playing online#

The creator chooses White, Random or Black. Random is resolved once, equally, by the server and never rerolled. The friend receives the opposite side. White moves first. Anyone holding an unfilled private invite can take the remaining seat; only seated players can read the game. Refresh preserves an anonymous session, but deleting browser storage loses that identity and cannot reclaim a seat in v1.

Lobby, clocks and match results#

The lobby lists games belonging to this browser identity under Your turn, Opponent’s turn, Waiting to start and Finished. Move numbers count pairs of plies, rounded up; a new game has zero moves. Guest names are trimmed plain text, 1–32 characters, and may be shared by different players. Each match retains the names chosen when its seats were filled. The browser remembers your latest name for the next invitation.

Rapid presets are 10 min, 10+5, 15+10, 20 min, 30 min (the default), and 60 min. Custom clocks allow 1–120 initial minutes and 0–60 increment seconds. 10+5 means ten minutes per player plus five seconds after each accepted move. Both players must explicitly click Ready before White’s rapid/custom clock starts. Repeating Ready does not restart either clock. Correspondence allows 1, 2, 3, 5, 7 or 14 days per move, starts when the friend joins, and resets the full allowance for each new turn without banking unused time.

Clocks keep running during disconnects, closed tabs and draw offers. Server time determines whether a move is on time: a move processed at or after its deadline loses to timeout, regardless of material. Timeout is a match result and does not alter the saved movement-engine position. Existing matches and local practice remain untimed. Timing uses the independent clock-v1 contract; strato-v1 and chess3-v1 movement semantics are unchanged.

The board starts in 3D and remembers your renderer preference. If WebGL fails it automatically opens playable 2D. Both views retain a selected piece when switching levels or renderers. Dots indicate quiet moves, rings indicate captures, a source border remains while a separate destination border marks the pending move, and a checked king is outlined. Promotion requires choosing Q/R/B/N before confirming. Arrow keys navigate the board, Enter/Space selects, and Escape cancels; in 3D All levels view, Page Up/Down moves the keyboard cursor between levels. Reset restores the initial orientation and framing without changing the game.