  The Moscow State University Extensive Air Shower (EAS-MSU) array studied
high-energy cosmic rays with primary energies ~(1-500) PeV in the Northern
hemisphere. The EAS-MSU data are being revisited following recently found
indications to an excess of muonless showers, which may be interpreted as the
first observation of cosmic gamma rays at ~100 PeV. In this paper, we present a
complete Monte-Carlo model of the surface detector which results in a good
agreement between data and simulations. The model allows us to study the
performance of the detector and will be used to obtain physical results in
further studies.
