Orthokon is a two-player game. Each player has four pieces at the start, arranged on opposite ranks of a 4x4 field.
 
A piece moves either diagonal or orthogonal through empty spaces, stopping only when encountering another piece or an edge of the playing field. It then changes all pieces which are orthogonally adjacent into pieces of its own color.
 
The game is won when the opponent no longer has any pieces or possible move.