  Over the last twenty years of research on quantum game theory have given us
many ideas of how quantum games could be played. One of the most prominent
ideas in the field is a model of quantum playing a 2x2 game introduced by J.
Eisert, M. Wilkens and M. Lewenstein. The scheme assumes that players'
strategies are unitary operations the players act on the maximally entangled
two-qubit state. The quantum nature of the scheme has been under discussion
since the article by Eisert et al. came out. The aim of our paper is to
identify some of non-classical features of the quantum scheme.
