MiniChess: A 41-Cell Cross-Grid Chess Variant with a Dual-Mode AI Engine

MiniChess is a chess variant played on a 41-cell cross-shaped board embedded in a 7×7 grid. The geometry preserves the central files and ranks of standard chess but removes the four corner 3×3 quadrants, yielding a smaller and more tactical game with shorter average game length. Each side has 12 pieces: a king, queen, two rooks, one bishop, one knight, and six pawns. The cross geometry forces three rule adaptations: rook- and queen-style horizontal/vertical slides skip the void cells between the cross arms, pawn forward motion likewise skips voids on the central files, and the rules omit castling, en passant, and the two-square pawn opening — none of which the geometry permits cleanly. This report specifies the rules, documents the iOS reference implementation, and describes the search engine, which is shared with a parallel standard 8×8 chess mode included for comparison and accessibility.