I will use this talk as an opportunity to introduce my scientific work to the members of the Formal Methods group. I will present the research I have done during my PhD on the semantic foundations of "probabilistic" modal mu-calculi. This is mostly based on Game Theory, but I will not assume any particular knowledge of the subject in my talk. If time permits I will also outline some of the work I have done during my previous Postdoc and in particular about the result I have presented last week at FoSSaCS 2013, Rome. During the talk I will try to emphasize the points I would like to investigate further during this year of postdoc here at CWI.