Fig. 2.

Phase portraits of classical games with $r_1=1$ and $r_2=2$. The payoff values and the qualitative behavior in (a) Prisoners' dilemma, (b) Hawk–Dove game, and (c) Stag hunt game are the same as in Fig. 1. However, the trajectories are different and the dashed lines in (b) and (c), given by $x_2/x_1=(a-c)/(d-b)$, are not invariant as in Fig. 1.