  We consider games with two antagonistic players --- \'Elo\"ise (modelling a
program) and Ab\'elard (modelling a byzantine environment) --- and a third,
unpredictable and uncontrollable player, that we call Nature. Motivated by the
fact that the usual probabilistic semantics very quickly leads to
undecidability when considering either infinite game graphs or
imperfect-information, we propose two alternative semantics that leads to
decidability where the probabilistic one fails: one based on counting and one
based on topology.
