The article explores how hard it is to find Nash equilibria in certain types of games. They found that it's impossible to determine if a Nash equilibrium exists when players use random strategies, but it is possible when they use fixed strategies. This is true even if there are restrictions on the rewards players can get. The problem of finding Nash equilibria is also unsolvable in some cases for turn-based games. However, when players use fixed strategies that don't change over time, the problem becomes solvable.