Blockmate: Cube Chess

Blockmate is chess played with a set of geometric blocks, in the spirit
of the 1924 Bauhaus workshop: the shape of a piece tells you how it moves.

A pawn is a small cube - one square forward. A rook is a bigger cube,
square and straight. A knight is a step, the exact L it jumps in. A bishop
wears a cross on its head: its two diagonals. A queen carries a sphere,
because she rolls any way she likes. And the king is a cube turned forty
five degrees - the odd one out, the one you cannot lose.

Everything a chess app should have and nothing it should not. Four
opponents, from one that will hand you a piece to one that thinks for
three seconds and does not. Two players on one phone. Take a move back,
ask for a hint, flip the board, read the move list in real notation.
Castling, en passant, promotion, stalemate, the fifty move rule and
threefold repetition are all in there, and the engine is checked against
the standard perft positions before every release.