In this chapter we give an overview on the theory of noncooperative games. In the first part we consider in detail for zero-sum (and constant-sum) noncooperative games under which necessary and sufficient conditions on the payoff function and different (extended) strategy sets for both players...

In this paper we discuss the level set method of Joo and how to use it to give an elementary proof of the well-known Sion's minimax result. Although this proof technique is initiated by Joo and based on the inter-section of upper level sets and a clever use of the topological notion of...