Example: Checkers

Checkers uses an 8×8 grid, 12 pieces per player, move vs jump (with mandatory jump), and kinging.

Entities

• mainGrid — Grid 8×8.
• checker — perPlayer, count 12, state isKing: false, displayProperties: ["isKing"].

initialPlacements put each player’s checkers on their first three rows.

Turn stages

• jumpIfPossible — activePlayers: currentPlayer in this stage. initialMoves: if NoPossibleMoves for jump, set stage to moveIfNoJump. moves: jumpChecker (MoveEntity with then: RemoveEntity on jumped piece, then SetActivePlayers to keepJumping).
• keepJumping — Same jump move; when no more jumps, SetActivePlayers to kingPieces.
• moveIfNoJump — initialMoves: PassTurn if no move. moves: moveChecker (MoveEntity one step diagonally), then SetActivePlayers to kingPieces.
• kingPieces — initialMoves: ForEach over spaces that Contains a piece and are on the back row (using Evaluate with coordinates and relativePath to player), SetState isKing: true; then EndTurn.

Move/jump destination conditions use relativeCoordinates with expression to choose direction by player (e.g. player == '0' ? [-1,1] : [1,-1]). InLine ensures the jumped piece is between source and destination.

End condition

endIf: Evaluate passCount > 0 (using gamePath to _meta.passedPlayers.length) → winner is expression (currentPlayer + 1) % 2 (opponent of who just passed).

Full definition: server/examples/checkers.json.