Enemy pieces are hidden blank discs until they capture.
How to play
Each side's 16 pieces start shuffled randomly across its first two rows (the king always on the back row), and enemy pieces appear as blank discs: their identity is hidden until they make a capture, which reveals them for good. Your own pieces are always visible to you. There is no check: win by capturing the enemy king, wherever it hides. Pawns promote to a queen (and stay hidden if unrevealed).