Board and starting pieces
Play on an 8×8 board. White starts. The kings are visible on e1 and e8; each side's other 15 pieces are covered in their normal starting squares. Their real roles are decided only when they first move. Kings never appear in the reveal pool.
How do the pieces move?
The ? badge marks a covered piece. Its symbol shows how it moves and attacks on its first move. After revealing, it follows its new role.
Move by the cover, then reveal
A cover moves, captures and attacks like its symbol: rooks along ranks/files, bishops diagonally, queens both, knights in an L, pawns forward with diagonal captures. Sliding pieces cannot jump; knights can. After a legal first move, reveal the moving piece and use its new role from then on. A covered rook can therefore become a knight at its destination.
Probabilities and captured covers
Each side starts with Queen 1, Rook 2, Bishop 2, Knight 2, Pawn 8. A reveal draws in proportion to the remaining counts and removes one of that role. Initially Queen is 1/15 and Pawn is 8/15. Capturing a covered piece does not reveal it or change its owner's pool. The remaining total equals covers still on the board plus covers captured before revealing.
Check and checkmate
Kings move one square and are never captured. A move must leave your own king safe. Covered enemy pieces attack by their covers; revealed pieces attack by their new roles immediately. If the player to move is checked and has no legal response, that player loses by checkmate. No legal move without check is stalemate and a draw.
Castling with a covered rook
Castling requires the king and corner rook to retain their castling rights, a clear path, and no check on the king's start, transit or destination squares. The corner must hold an unmoved rook cover or an eligible revealed rook. O-O moves e1→g1 and h1→f1; O-O-O moves e1→c1 and a1→d1, mirrored for Black. A covered rook reveals on that same move. Moving or capturing the corner piece removes that right permanently.
Pawns and en passant
White pawns advance toward rank 8, Black toward rank 1. A pawn on its home pawn rank may advance two squares if both are clear. A two-square pawn-cover move creates en passant only if the piece reveals a Pawn. If it reveals another role, no en passant is allowed. The right expires after the opponent's next move; en passant may not expose your own king.
Promotion and underpromotion
A revealed pawn reaching the last rank promotes to Queen, Rook, Bishop or Knight. A cover of any role that arrives there and reveals a Pawn also promotes immediately. Choose the conditional promotion before confirming that move; the choice only applies if a Pawn is revealed. It cannot influence which role is drawn. The move, reveal and any promotion count as one turn.
Repetition and draw limits
Claim a draw after three identical positions or 50 moves per side without a capture, pawn move or reveal. A non-revealing intended move may support the claim. Identical positions require the same board, covers, pools, turn, castling rights and usable en passant. Five repetitions or 75 quiet moves per side draw automatically; checkmate takes priority. Insufficient-material draws are evaluated only after all surviving covers have revealed. Unused pool entries for captured covers cannot return to play.
Play, clocks and saved games
Find an online opponent, invite a friend, play together on one device, or choose one of five computer levels. Online clocks follow your room settings; running out of time loses unless the opponent cannot possibly mate. Resignation loses and an agreed draw ends the game. Completed reveals stay fixed when you reconnect or replay. The computer considers the same remaining possibilities you can see.
What should beginners watch for?
Plan the first move using the cover piece's movement. After the reveal, reassess threats using the revealed identity; do not treat the cover as permanent.
Rules and references
- ChessPlayX — online rules published on this page
This guide describes play on ChessPlayX. Platform-specific conventions are stated in the relevant sections; tournament administration may differ.