Playing Raumschach

Raumschach is an old german version of spatial chess. It was invented by Ferdinand Maack in 1907. It need more pieces than in chess for each player:  two pawn and two new pieces; the unicorns . This spatial chess is played in a 5x5x5 board (like a cube). Of course it is hard to play. 

In this example, the knight is giving check to king from the third level to the first.